A little question on crop factor

[baofeng]

I am choosing between whether to buy a Canon or Olympus DSLR for birding. I am wondering why so many people here choose Canon when Canon crop factor is 1.5x while Olympus is 2X. It is about 1.4 times extra and wouldn't it be wonderful for birding? Why do birders here like to choose Canon DSLR and for the sake of extending their reach, they buy teleconverter which causes them to lose f-stop. Why don't they use Olympus DSLR instead. I sure they is a reason but I cannot find the reason anywhere.

[AC/DC]

The crop factor is by no means everything. Having a smaller sensor means increased noise problems. The Canon crop factor on an APS-C sensor is 1.6X - Nikon's is 1.5X.
Canon and Nikon are established brands with a huge range of accessories and lenses. They produce more lenses suitable for birding than olympus do. They offer more upgrade possibilities, and their high end bodies are probably better - at least in terms of noise. The popularity of the two companies means more lenses and accessories can be found secondhand, too.
If olympus could offer a decent 400mm lens, then maybe more people would seriously consider the system.

[tdodd]

I agree with AC/DC, but I'd go further, and caution you that a higher crop factor does nothing at all to make your subject bigger. It does not yield any extra magnification. See if this post helps explain what I am talking about....

http://www.birdforum.net/showpost.php?p=1534042&postcount=129

I also have no idea how good the Olympus AF system is for action, like BIF, for example.

[Keith Reeder]

While I agree with Tim that there's no "real" magnification from a crop (and used to argue quite vehemently along the lines of Tim's comments) I've been converted to the view that - in practice - you do get this benefit.

See "Expt. 1" on this page (http://www.ophrysphotography.co.uk/pages/tutorialfullframeandcrop.htm)for what you get from a crop compared to a full frame sensor (at least before you start cropping, which is of course a whole other subject): hard to deny that you get a bigger subject in frame from a cropper.

For me, it's the noise issue that is the main "problem" with Four Thirds and similar itty-bitty sensors - that's why compacts (which have tiny sensors) rarely have anything like decent noise abilities.

There's also the important point, as mentioned by Steve, that Canon and Nikon have a range of excellent long lenses, many with IS/VR, at (relatively) realistic prices, that Olympus et al don't get anywhere near.

[tdodd]

(at least before you start cropping, which is of course a whole other subject)
But the cropping is the whole point of the crop factor "argument". If your glass is too short then you will be cropping. Stick a 400mm lens on a 5D2, 1D3, D300, 50D or something from Olympus and if 400mm is too short on the Olympus it will be too short on all the others too. You will end up performing a software crop on images from all the cameras and you will end up with exactly the same useful area of sensor remaining, regardless of which camera you used. It might be 12x8mm; It might be 8x6mm, but to achieve the same composition you will end up with the same area of sensor being used from all the cameras. At that point the discussion about crop factors is moot. All the cameras will have been software cropped to exactly the same crop factor, meaning no difference whatsoever in terms of image size from any of them.

The idea that "crop factor" contributes to some sort of image magnification is preposterous. It doesn't. All that crop factor does is to narrow your angle of view, save you money on the camera and possibly reduce the file sizes you have to process. A crop viewfinder will make it more difficult to locate a small bird in the frame when using a long lens, possibly very difficult at times. A camera with a larger sensor, wider angle of view, and full 100% viewfinder display will assist you in locating your subject quickly.

As for "small" sensors having the worst IQ, again, if you are cropping images from each sensor down to the same physical size, in mm, then to all intents and purposes all your sensors are the same size. If the pixel structure was identical between cameras and the only difference was the sensor size then there wouldn't be a scrap of difference in IQ from any of them, once you'd cropped the image down to the same sensor area.

What then differentiates the cameras is the IQ per square mm of sensor area and that is a whole lot harder to get to grips with since there are so many variables to consider.

At the end of all that, let's not forget that there may be times when your lens is far from too short, and you have no trouble filling the frame. Well, now it's a very different story. The larger the sensor area you can project your subject/scene onto, the more light you will gather and the better the IQ you will achieve. This is the time when the limitations of little sensors reveal themselves and the larger sensor take an overwhelming lead in IQ.

IQ is principally driven by the amount of light gathered. You gather more light by projecting a larger image onto a larger sensor area. To get a larger image you need longer glass. Fiddling around worrying about pixels, pixel densities and per pixel noise is neither here nor there, relatively speaking. What counts, primarily, is the area of sensor put to good use. It's that simple.

Is a 4/3 camera with a 50mm lens going to give a 5D, 5D2, 1Ds3, D3 or D3x and 100mm lens a run for its money? No, not in a million years. A 4/3 sensor has approx 40% of the area of an APS-C sensor, which itself has an area only ~40% as large as a full frame camera. 40% of 40% is only 16%, a lot better than a point and shoot but a long way from the big boys.

Buying into 4/3 is likely retreating away from full frame and heading back into the woods with the point and shoot cameras. It's the wrong direction to be heading in if IQ is your concern. If cropping tighter was the solution to improving IQ I'm not sure there would be the market there is for 500/4, 600/4, 800/5.6 lenses and teleconverters on top. Where is the upgrade path from the 4/3 system?

Now, I don't want to be mean about the 4/3 system, but its appeal must surely lie in its compact size and modest entry level price for a body and quite a bit of focal length. But where do you go when 300mm is no longer enough? Remember, the magnification from a 300mm lens on an Olympus body is no different than 300mm on a Canon or Nikon, despite the impression the "crop factor" gives to some people.

[Keith Reeder]

"Preposterous" or not Tim, the subject is bigger in the frame in images from croppers - there's just no denying that.

If that doesn't add up to "magnification" - for want of a better phrase - then nothing does: it has the same effect in terms of the size of the subject in the frame as a TC of the same magnification.

[tdodd]

The subject is the same size. The frame is smaller. That is the more accurate way to look at it. It also happens to be a physical fact. To suggest otherwise only serves to perpetuate the myth that croppers give you greater magnification.

[goodwin912]

It's not just the magnitude of the crop but the sensor that you also have to take into account.

A 12MP sensor with a 1.fx crop will produce (on screen) the same size image as a 12MP full frame sensor, as dictated by the number of pixels present.

However, the crop camera image will give a magnification in this case, it will be physically the same size image (in terms of pixels) but the crop camera image will show the subject much tighter in the image space.

This theory only works with the same size of sensor though, if you put it into real terms and play off two manufactured DSLR's. Full frame cameras always have a larger number of pixels so cropping on the computer to the same factor as the crop sensor models produces similar or superior results depending on the cameras in question.

I also echo what others say about noise and other issues with smaller sensors, this post is just about the physics of the image space and sensor type.

Cheers, Rich

[AC/DC]

"Preposterous" or not Tim, the subject is bigger in the frame in images from croppers - there's just no denying that.

If that doesn't add up to "magnification" - for want of a better phrase - then nothing does: it has the same effect in terms of the size of the subject in the frame as a TC of the same magnification.

+1 Keith. You can't argue with the fact that a 1.6X cropper with the same or more pixels than 1.3X or ff body will mean slightly more percieved reach.

[tdodd]

Steve, why are you confusing the issue by introducing pixels to the subject? The discussion is supposed to be about crop factors, not pixels.

If you must talk about pixels then consider that a full frame 5D2 and a 1.6X crop 30D have the same pixel density. Does a 30D have any advantage over a 5D2 in terms of "reach" due to its crop factor? No. Of course not. Crop factor does not affect reach or subject magnification.

I might be persuaded that you can take advantage of increased pixel density to pretend you have more reach, but that's nothing to do with the crop factor. That's to do with the pixel density. If it's all about pixel density then a 50D has more reach than a 40D and a 40D has more reach than a 30D. But they all have the same crop factor, so again crop factor apparently doesn't affect reach/magnification after all.

So what really contributes to reach - i.e. real magnification of the subject? It's not crop factor. It's not pixel density. It is focal length.

[AC/DC]

Steve, why are you confusing the issue by introducing pixels to the subject? The discussion is supposed to be about crop factors, not pixels.

If you must talk about pixels then consider that a full frame 5D2 and a 1.6X crop 30D have the same pixel density. Does a 30D have any advantage over a 5D2 in terms of "reach" due to its crop factor? No. Of course not. Crop factor does not affect reach or subject magnification.

I might be persuaded that you can take advantage of increased pixel density to pretend you have more reach, but that's nothing to do with the crop factor. That's to do with the pixel density. If it's all about pixel density then a 50D has more reach than a 40D and a 40D has more reach than a 30D. But they all have the same crop factor, so again crop factor apparently doesn't affect reach/magnification after all.

So what really contributes to reach - i.e. real magnification of the subject? It's not crop factor. It's not pixel density. It is focal length.

Erm, perhaps because it is relevant to the issue of the crop factor? Besides, goodwin introduced the idea of pixels.

I agree that in theory the crop factor offers no more magnification, but the reality is that a lot of cropper cameras do give more magnification because of the amount of pixels they have. Yes, I know it's not the same as the crop factor, but this discussion is also about pixels. The OP didn't say 'lecture me on the crop factor please'. It so happens that the OP realises that the 2X crop factor of the olympus cameras is an advantage over the canon and nikon crop factors. He wanted to know why people choose canon over olympus despite this.

[Mono]

Assuming we are taking pictures of birds in the distance a 1.6 (or whatever) crop factor camera will land more pixels on target than a same pixel count camera with a full frame. The wanted bit of the image (the bird) will be bigger. If you want to make that bird bigger with the full frame camera you will need more mms of glass. That ammounts to an increase in real world maginfication. Yes we all know a 400mm lens will be a 400mm lens no matter what body you attach it to, but for little things a large way away crop factor does mean more pixels on target.

[Roy C]

Although we all know that the crop factor is not the same as an increase focal length etc....... I have notice these days that even some of the biggest names in bird photography often refer to croppers as having more 'reach'.
Just to thrown in a bit of useless info - It is interesting to note that for a full frame camera like the 5D II which starts with 21mp it ends ups with just 8.2mp when cropped to the same FOV as a 1.6 cropper.Likewise the 1.3 crop 1D mkIII is reduced to around 5.8mp when cropped to a 1.6 cropper FOV (this is by my dubious reckoning anyway so I stand to be corrected).

edit: just seen Mono's post above and I agree entirely.

[AC/DC]

I'm glad to see I'm not the only one on this wavelength - what Mono said is very similar to what I said when quoting Keith.

[tdodd]

Just to thrown in a bit of useless info - It is interesting to note that for a full frame camera like the 5D II which starts with 21mp it ends ups with just 8.2mp when cropped to the same FOV as a 1.6 cropper.
It's not useless info. It is very much to the point. A 30D does not have more reach than a 5D2. None at all. They have equal reach because they have equal pixel density. I already made that point in post #10.

Following this argument further, a 30D actually has less reach than a D3X, because it has a lower pixel density.

The point of all this is that the reach comes from pixel density, not crop factor. Crop factor has bugger all to do with it.

Whether that extra reach is useful/useable is a whole other topic, since some people feel the 50D, with its high pixel density, offers no improvements over the 40D in terms of IQ. It may be interesting to note that an Olympus E-620 has a higher pixel density than the 50D, at 5.1MP per square cm vs 4.5. Does that mean the Olympus might have more reach but the IQ is even worse? One thing is certainly true - the higher the pixel density the higher quality your glass needs to be and the better you need to be as a photographer, since any tiny error in focus, shake, blur, diffraction will be picked up more readily, thus reducing or completely negating any advantage in "reach". You'll also need better light, or the noise will intrude more for any given ISO if you try and stare at those tiny pixels individually.

p.s. An Olympus E-450 only has 4.1MP per square cm, giving it less "reach" than a 50D. It's NOT the crop factor.

p.p.s A Canon Powershot SX200 IS has a pixel density of 43MP per square cm, almost 10X the density of a 50D. Does that give it more useable reach, for birding, than a 50D? I have my doubts. Up to a point, higher pixel density can improve IQ, but beyond that point it all goes downhill as you rob Peter to pay Paul.

If you want quality you want a large sensor, filled with lots and lots of really big pixels (think 5D2), and a huge lens to make full use of all that lovely sensor area.

[goodwin912]

Seems to all that everyone is arguing the same case.

Crop factor can make a certain differance in smoe applications but is by no means a reason to buy a specific camera.

Canon offer much better quality lenses and accessories to go with it's cameras. Being one of the forefront manufacturers is caught in a kind of 'arms-race' with Nikon to constantly update and develop it's line up.

The best possible lens for an olympus camera is a £5.5k 300mm f2.8, and no doubt we have all drooled on our keyboards over canon's 1200mm f5.6.

Summary : crop factor is not the be all and end all of bird photography.

Rich

[baofeng]

Seriously, do anyone use Canon SX10 for birding? It has high pixel density, f5.7 at 560mm, and it 5X cheaper than a decent DSLR. However, with such a small sensor (crop factor ~6), I believe that the equivalent lens that is mounted on it is a 100 (560/6) mm lens. Anyway, Sony even has the same offering at 560mm too, f5 at max telephoto.

Soon, I am going to get a DSLR with crop 1.6X. I am going to mount a 100mm lens on it and focus on some distant objects and compare it to my Canon SX10 (will crop the DSLR later). Any guess who will be a winner?

I will also use a 200mm lens and do the same test comparing it to SX10. Any guess which one will be a winner?

[tdodd]

I will happily put my 50D and 100-400 zoom lens (640mm equivalent at the long end) at 400mm (640mm) and f/5.6 up against an SX10 at "560mm" and f/5.7 and compare results.

Here's an example shot yesterday, handheld at 400mm (560mm equivalent), 1/800, f/5.6, 400 ISO. First the full image, then a 100% crop....

If an SX10 can deliver results to compete then I will be very impressed.

EDIT : I've added another shot/crop from a week ago, again with the 50D and 100-400, this time at 400mm, 1/1000, f/5.6, 400 ISO and with +2/3 increase to exposure in Lightroom. Sharpening is at Lightroom defaults.

I should add that as a birding photographer, or any sort of photographer, I have a long way to go, so these are certainly nothing special, but I think the equipment did quite well, all things considered.

[baofeng]

I will happily put my 50D and 100-400 zoom lens (560mm equivalent at the long end) at 400mm (560mm) and f/5.6 up against an SX10 at "560mm" and f/5.7 and compare results.

Here's an example shot yesterday, handheld at 400mm (560mm equivalent), 1/800, f/5.6, 400 ISO. First the full image, then a 100% crop....

If an SX10 can deliver results to compete then I will be very impressed.

EDIT : I've added another shot/crop from a week ago, again with the 50D and 100-400, this time at 400mm, 1/1000, f/5.6, 400 ISO and with +2/3 increase to exposure in Lightroom. Sharpening is at Lightroom defaults.

I should add that as a birding photographer, or any sort of photographer, I have a long way to go, so these are certainly nothing special, but I think the equipment did quite well, all things considered.

That was impressive. As it is night time in Singapore where I live, I have to wait till tomorrow before taking a picture. However, I can assure you that SX10 cannot take sure photo that can withstand so much cropping.

[JohnZ]

I am probably being a bit dim here but the pics from Keiths link all look the same size to me. Therefore as the image from a cropping camera is that much larger then....... ?

[Roy C]

(560mm equivalent at the long end) at 400mm (560mm) and f/5.6 up against an SX10 at "560mm" and f/5.7 and compare results.

Here's an example shot yesterday, handheld at 400mm (560mm equivalent), 1/800, f/5.6, 400 ISO. First the full image, then a 100% crop....


That Swift crop is impressive - when you say 560mm I assume you were using a 1.4tc or did you mean 640mm ?

[Nikon Kid]

Is there really any point in hard cropping a distance bird, the only thing I would think its good for is ID of a certain species, Now none of you would put them hard crops in your gallery would you ? I am afraid when its said these are good shots they look c**p to me.

I know I wear glasses and all that, but my eyesight is not that bad :eek!:|8)|:cool:

[tdodd]

That Swift crop is impressive - when you say 560mm I assume you were using a 1.4tc or did you mean 640mm ?
Oops, I mean 400mm X 1.6 for the crop factor = 640mm. Obviously 560mm is one of the figures that sticks in one's head, because of teleconverters, and I plucked it out of my memory instead of doing the maths.

So those shots were at 400m actual, 640mm AOV allowing for the crop. I shall correct my original post.

While out today I spotted this fellow, shot once again with my handheld 50D, 100-400 at 400mm (640mm equivalent!), 1/1000, f/6.3, 400 ISO and converted from raw to JPEG in Lightroom with no edits.

First is a shot from a little way away, full frame and a 50% crop. Then I moved a little closer and took another shot, which I've also included as a full frame, a 50% crop and a 100% crop....

[AC/DC]

To John Z, if you look @ the pictures of the butterfly chart thingy, you'll see there are differences in size.

Tim, I've read this a couple of times now, and I get your points a bit more - I think when people talk about the crop factor though, they almost always talk about pixels in addition - the fact that something like the 40D is a 1.6X cropper means it has a higher pixel density than a 1dmkiii despite the same number of pixels - but people (me included) say that it has a greater reach than something like a 1dmkiii because of the crop factor - when in fact it is the higher pixel density caused by the cropped sensor, which isn't really the same thing, although still closely linked to the crop factor. Or am I talking nonsense!

[tdodd]

Is there really any point in hard cropping a distance bird, the only thing I would think its good for is ID of a certain species, Now none of you would put them hard crops in your gallery would you ? I am afraid when its said these are good shots they look c**p to me.

I know I wear glasses and all that, but my eyesight is not that bad :eek!:|8)|:cool:
Terry, anyone who actually wants to make use of a 100% crop as their actual photo is, in my opinion, really clutching at straws. That is no way to do photography. I put the examples up merely to illustrate what the 100% crops look like. Quite frankly, if you are having to use an image from a 50D at anything over 50% viewing magnification then you are too far away from your subject and/or your glass is too short. The problem with digital is that it makes it too easy to pixel peep, and that's when people whinge and moan about per pixel noise, and sharpness, instead of looking at the actual images produced when they perform their photography properly.

Staring at a 50D image at 100% on a screen from 12-18" away is, quite frankly, madness, but some people like to do it. A 50D image viewed at 100% is equivalent to the whole frame being blown up to around 4' across. That is an insane amount of magnification at which to judge IQ. Quite honestly it shouldn't be allowed. That is why the 50D gets a bad press. It's because of idiotic pixel peeping as a substitute for making use of the whole sensor area you paid for.

If pro quality printing requires 300 pixels per inch then a 50D might be good for prints up to 4752/300 = 16" across. That's pretty much the size of a 17" monitor, just a little more. So, to be honest you should be looking at 50D full frame images at approx "fit to screen" size to see if the are up to snuff. That's actually pretty close to viewing at 33% on my system. It may be even less on monitors with lower resolution than my 1920x1200 screen.

I think it's fair to say that for 100% crops of BIF, from a 50D and a zoom lens, those images are not bad at all. As actual useable images they are indeed poop.

All of this really reinforces my point that quality comes from bigger glass and more silicon, not cropping ever tighter onto tinier and tinier and noisier and noisier pixels.

I would recommend that people consider 35mm as a baseline for making photographic judgements and that instead of working in terms of pixels they work in terms of magnifications from that captured image. e.g. a 35mm frome is 36mmx24mm. To make a 12x8 print from a 35mm frame requires a modest magnification factor of 8X. If you take the whole image from a 1.6X cropper then to generate a 12x8 print from that you will need to magnify the captured image by almost 13X. That is a significant increase in magnification that will emphasise noise/grain, shake, blur, misfocus, diffraction etc.. If you then make heavy crops into a 1.6X sensor, or use an even smaller sensor to begin with, like a 4/3 or compact sensor then to get a 12x8 print at decent quality is asking a lot. Forget the chuffing pixels. Look at the real magnifications you are dealing with based on the actual physical size of the image you have captured vs the final product you want to create. When you expect perfect image quality from a 50X magnification of the captured image is the time you should realise you are doing something wrong. Very wrong.

p.s. A 50D image viewed at 100% on my screen is equivalent to a physical magnification of 40X. Is it any wonder that it doesn't look perfect?

p.p.s. At that sort of magnification you can also chuck your DOF calculator out the window. Your DOF will be damn near 0, for a bird photo with a long lens.

[tdodd]

Steve, you are spot on with that last post. Yes, there is a relationship between total number of pixels, sensor size/area and pixel density but the only value which, on its own, defines "reach" is the density. Keep the density the same and you can have any size sensor you like - the reach will be the same.

I think when people talk about the crop factor though, they almost always talk about pixels in addition
I think they almost always do not, and that is the crux of the problem. Look at the first post again. Baofeng appears to be under the illusion that "reach" comes purely from crop factor. Not a mention of pixels or pixel density anywhere. It's a perfect illustration of the confusion and misunderstanding that is perpetuated by people who keep referring to crop factor rather than pixel density affecting reach.

These people who yammer on about crop factor increasing reach need to qualify their remarks by also discussing the number of pixels involved at the same time, but they often don't. They simply say "a crop camera give more reach than a full frame camera". That's nonsense. What they need to say is that "a crop camera with the same number of pixels as a full frame camera will have more reach". Kerching! Yes. So why not just say higher pixel density gives more reach, in the first place. Why confuse things by talking about crop factor. That influences nothing on its own except angle of view.

[Nikon Kid]

Terry, anyone who actually wants to make use of a 100% crop as their actual photo is, in my opinion, really clutching at straws. That is no way to do photography. I put the examples up merely to illustrate what the 100% crops look like. Quite frankly, if you are having to use an image from a 50D at anything over 50% viewing magnification then you are too far away from your subject and/or your glass is too short. The problem with digital is that it makes it too easy to pixel peep, and that's when people whinge and moan about per pixel noise, and sharpness, instead of looking at the actual images produced when they perform their photography properly.

Staring at a 50D image at 100% on a screen from 12-18" away is, quite frankly, madness, but some people like to do it. A 50D image viewed at 100% is equivalent to the whole frame being blown up to around 4' across. That is an insane amount of magnification at which to judge IQ. Quite honestly it shouldn't be allowed. That is why the 50D gets a bad press. It's because of idiotic pixel peeping as a substitute for making use of the whole sensor area you paid for.

If pro quality printing requires 300 pixels per inch then a 50D might be good for prints up to 4752/300 = 16" across. That's pretty much the size of a 17" monitor, just a little more. So, to be honest you should be looking at 50D full frame images at approx "fit to screen" size to see if the are up to snuff. That's actually pretty close to viewing at 33% on my system. It may be even less on monitors with lower resolution than my 1920x1200 screen.

I think it's fair to say that for 100% crops of BIF, from a 50D and a zoom lens, those images are not bad at all. As actual useable images they are indeed poop.

All of this really reinforces my point that quality comes from bigger glass and more silicon, not cropping ever tighter onto tinier and tinier and noisier and noisier pixels.

I would recommend that people consider 35mm as a baseline for making photographic judgements and that instead of working in terms of pixels they work in terms of magnifications from that captured image. e.g. a 35mm frome is 36mmx24mm. To make a 12x8 print from a 35mm frame requires a modest magnification factor of 8X. If you take the whole image from a 1.6X cropper then to generate a 12x8 print from that you will need to magnify the captured image by almost 13X. That is a significant increase in magnification that will emphasise noise/grain, shake, blur, misfocus, diffraction etc.. If you then make heavy crops into a 1.6X sensor, or use an even smaller sensor to begin with, like a 4/3 or compact sensor then to get a 12x8 print at decent quality is asking a lot. Forget the chuffing pixels. Look at the real magnifications you are dealing with based on the actual physical size of the image you have captured vs the final product you want to create. When you expect perfect image quality from a 50X magnification of the captured image is the time you should realise you are doing something wrong. Very wrong.

p.s. A 50D image viewed at 100% on my screen is equivalent to a physical magnification of 40X. Is it any wonder that it doesn't look perfect?

p.p.s. At that sort of magnification you can also chuck your DOF calculator out the window. Your DOF will be damn near 0, for a bird photo with a long lens.

Why is it Tim you are so clever, good answer as usual :t:

[tdodd]

Why is it Tim you are so clever, good answer as usual :t:
It's actually because I have been giving this subject a lot of thought lately and it has become all too clear to me how absurd it is to expect faultless IQ from a 50D when viewing at 100%.

By dragging things back to 35mm film, as a baseline for applying certain rules of photography (DOF for starters, SS >= 1/FL for another, physical image magnification for a third), only then can we appreciate how unrealistic our expectations have become, compared with what has gone before

Consider that images in real life - in nature - are not digital things. Light passing through a lens has infinite detail and tonal variation. Our eyes, to all intents and purposes are analogue devices. We do not see the scenes before us represented as bundles of little dots. Our vision is one continuous, seamless representation of the light coming from the scene before us.

By digitising a scene with a camera we chop it up into tiny little bits (pixels). If you have a low resolution capture device (say a 30D) then you only approximate what each piece of the puzzle should really look like, relatively crudely. By increasing pixel density, and chopping the captured image into finer and finer pieces, such as with a 50D, we increase the precision with which we capture that image data. But there is no more "image" coming through the lens whether it is a 30D or a 50D capturing it. The photon count is the same for any given area of silicon. A 50D pixel will capture fewer photons than a 40D pixel. It should come as no surprise that a 50D pixel has more noise. But assemble all the 50D pixels back together again, to form a whole image, and the noise should be about the same as the whole image from a 40D.

The benefit of the finer granularity of detail captured by the 50D is not so that you can blow it up larger than a 30D or 40D image. It is so that with the two images compared side by side, at the same physical magnification, the 50D version will contain finer detail throughout. The 50D does not give you an excuse to magnify the image from a 50D by 1.4X larger than that from a 30D or 1.22X larger than a 40D. Magnify them equally and enjoy the superior detail from the 50D. Do not magnify the 50D image 1.4X more and then complain that you can see noise, and it is soft.

This is very much a case of the whole being greater than the sum of the parts. Do not look at the parts (pixels). Look at the whole - the image - at a reasonable level of magnificaction.

At the risk of repetition, this brings me back one again to the issue of sensor area and the focal length being the main influences on IQ. The way to really improve your IQ is to capture more photons from your subject. The way to capture more photons is to use longer glass to optically magnify the image from your subject more. Then you can use a large sensor area with which to capture that image. All this pratting about jiggling pixel densities doesn't really alter how much light you captured. It might chop it up into smaller chunks, which in itself is not necessarily a bad thing, but it won't make a step change in IQ. Is there a massive leap (or drop) in IQ from the 30D to 40D to 50D? Not really. Is the IQ from an xxD body any better than from an xxxD body? Not really. Is the IQ from a 1D3 better than from any 1.6X cropper, when coupled with glass 1.3X longer? Hell, yeah. Is the IQ from a 5D2 the best of the lot, when coupled with suitable glass? You bet you. Is IQ going to increase by buying a 4/3 body and pretending your 200mm lens is really 400mm? Not on your life.

So, does a higher pixel density really give you more reach after all? Well I'd be very careful there. Maybe, a little, but not as much as you might hope/think. You can only spread those photons so thin, and if you haven't got enough of them captured then you can't spread them very far.

[Roy C]

Is there really any point in hard cropping a distance bird, the only thing I would think its good for is ID of a certain species, Now none of you would put them hard crops in your gallery would you ? I am afraid when its said these are good shots they look c**p to me.

I know I wear glasses and all that, but my eyesight is not that bad :eek!:|8)|:cool:
Terry,I regularly use heavy crops for web images, attached are some 100% crops that may not be up to the standards of a lot of people but they are good enough for me for web use. Certainly not up to your standards Terry but like I have said before one man's meat is another man's poison, we all have different standards.
p.s. we have not all got managed reserves and semi tame birds to shoot at ;)

[tdodd]

Roy, not a bad set there at all :) The clarity indicates great skill/technique on your part. The thing is, that's as far as you can go with those images - small webshots. If those are all 100% crops, they will never make it to a print to hang on the wall, or be fit for sale to the public at large. That's in no way a criticism of what you have there at all, but we do shoot for different reasons.

Personally I am not hugely interested in accumulating a whole bunch of web sized images. I want to shoot stuff I can sell, or at least enjoy full screen on my 40" 1920x1080 HDTV. Quite honestly, it is asking a lot of me and my gear to get an image of a moving subject, like a BIF, from my 50D and 100-400 that will fill a 1920x1080 screen, with a nice composition and large subject, and which looks sharp and clean at 100%. I'd far rather have 3840x2160 pixels, resized to 50%, which means I have some room to crop, but not a lot. Now, for a perched or fairly staic bird I might manage to get away with a 100% crop, but even that is not enough if my subject is too small to make a nice composition at those pixel dimensions.

Most of the bird related stuff I shoot ends up as "practice shots" because I am simply not close enough to get an image that suits my quality objectives. They might suffice for sharing on a web forum, for a bit, but many of them are not going to be keepers.

[Roy C]

Roy, not a bad set there at all :) The thing is, that's as far as you can go with those images - small webshots. If those are all 100% crops, they will never make it to a print to hang on the wall, or be fit for sale to the public at large. That's in no way a criticism of what you have there at all, but we do shoot for different reasons.

Personally I am not hugely interested in accumulating a whole bunch of web sized images. I want to shoot stuff I can sell, or at least enjoy full screen on my 40" 1920x1080 HDTV. Quite honestly, it is asking a lot of me and my gear to get an image of a moving subject, like a BIF, from my 50D and 100-400 that will fill a 1920x1080 screen, with a nice composition and large subject, and which looks sharp and clean at 100%. I'd far rather have 3840x2160 pixels, resized to 50%, which means I have some room to crop, but not a lot. Now, for a perched or fairly staic bird I might manage to get away with a 100% crop, but even that is not enough if my subject is too small to make a nice composition at those pixel dimensions.

Most of the bird related stuff I shoot ends up as "practice shots" because I am simply not close enough to get an image that suits my quality objectives. They might suffice for sharing on a web forum, for a bit, but they aren't going to be keepers.
Tim, each to their own, I am not worried about printing and at my age I am not remotely interested in selling pics (I have given away some prints to local birders but would never charge anyone). I do it purely as an hobby in my old age. I am also not interested in travelling far to get shots, I am strictly a local patch man and my only goal it to get web size shots of birds on my local patch.

The whole point of me supplying these pics is because someone suggested that nobody puts heavy crops in their gallery - my guess is that quite a lot of shots submitted to the galley are big crops.

[tdodd]

Fair point, Roy. I don't travel far for my birding photography either. In fact I just grab the breaks as they present themselves when I'm out walking the dog. You certainly won't catch me couped up for hours in a hide waiting for something to happen. Of course, that approach does severely limit my chances to nail award winners, but once in a while opportunity knocks. :)

At best I might drive 7 miles to my nearest RSPB reserve, but quite frankly that is a massive disappointment, photographically speaking. It's like someone paid no heed to the direction of the sun when laying out the boardwalks, and the opening hours give you no chance to shoot during early morning sunshine, when the light is coming in from the side and lighting the underside of the birds. With a 400mm lens, even on a 50D, it's too far to get anywhere near filling the frame with a single bird and I don't bother with flocks, birds on the ground or (with a few exceptions) in the water. Might as well leave the camera at home :(

What is the point in only opening from 09:30 to 17:00 in summer? The best light is between 05:00 and 07:00 and then again from 19:00 onwards. The rest of the time the sun is too high for optimum results.

[QuantumTiger]

I think they almost always do not, and that is the crux of the problem. Look at the first post again. Baofeng appears to be under the illusion that "reach" comes purely from crop factor. Not a mention of pixels or pixel density anywhere. It's a perfect illustration of the confusion and misunderstanding that is perpetuated by people who keep referring to crop factor rather than pixel density affecting reach.
I think there is a combination of factors here. Firstly people often use terminology (crop factor, magnification, megapixels, resolution) without being precise about what it means. Secondly there is a tendency to think in terms of single factors (eg to solve problem a I need to do b). Most situations are not single factor. Thirdly many people struggle with photography because they're not used to dealing with non-linear effects. Pretty much everything in photography revolves around square numbers (because photographs are areas) and that doesn't help. (For example doubling the number of pixels does not double resolution, it increases it by 1.4x)

For such reasons it is better to avoid talking in abstract terms and use real world examples. I've owned three eight mega-pixel cameras. A Minolta A2 (4x), an 20D (1.6x) and 1D MkII (1.3x). If I take a photo with any of these cameras at f/4 with a focal length of 50mm and print it at A4 I will have the same resolution image (in terms of pixels per inch). The Minolta image, however will look signifcantly zoomed in (equivalent to a 200mm lens). In terms of IQ printed at 6x4 there will not be much in it although the colour balance of the 1D is significantly better.

If I never actually crop my images then the argument about whether the A2 genuinely gives a higher magnifcation or not is irrelavent. To all practical purposes it gives me a closer view of the subject and for most people that is enough.

The 4x crop sensor has several advantages over the SLR. I'm dealing with a 50mm image so camera shake is less of a problem than with a 200mm lens - I can hand hold at slower shutter speeds. The depth of field also is the depth of field of a 50mm lens at f/4 not a 200mm lens at f/4 so it is not as narrow. It is also smaller, lighter and much less conspicuous. I tended to carry it more often and take more photos.

Fret not though. It also has a number of significant disadvantages over the SLR. I can't change lenses - and the lens on the camera is nowhere near as sharp as my L glass 70-200. I can start to see softness as I enlarge as well as other lens distortions. The noise characteristics are much worse too so if I crop in to get equivalent field of view to 400mm shot I can really start to see problems with the image even at 100 ISO.

On the other hand if I stick a 400mm lens on the 1D the image is much sharper, and the noise characteristics are much cleaner. I can crop my 400mm image to equivalent 800mm field of view and it is still very usable at 400 ISO.

Between the 20D and 1D there is much less difference. 1.6x to 1.3x is much less of jump than I had expected, but the larger pixels of the 1D are definately (but slightly) better quality!

The bottom line is they are all good cameras. For landscape work I miss the depth of field of the A2 and my shoulders didn't ache at the end of the day! For wildlife I would not be without my SLR. For me the decrease in crop factor from the 20D to the 1D was not biggest change. The 1D gets more shots - it's that simple. The biggest differences are autofocus accuracy, shot-to-shot speed, overall IQ and colour balance. I suppose what I'm saying is worry less about the numbers, because most modern cameras are beyond the point were detailed analysis will reveal one as much better than another. Worry instead about the things that actually help you get the shot.

Apologies for the long post!

[Roy C]

Fair point, Roy. I don't travel far for my birding photography either. In fact I just grab the breaks as they present themselves when I'm out walking the dog. You certainly won't catch me couped up for hours in a hide waiting for something to happen. Of course, that approach does severely limit my chances to nail award winners, but once in a while opportunity knocks. :)

At best I might drive 7 miles to my nearest RSPB reserve, but quite frankly that is a massive disappointment, photographically speaking. It's like someone paid no heed to the direction of the sun when laying out the boardwalks, and the opening hours give you no chance to shoot during early morning sunshine, when the light is coming in from the side and lighting the underside of the birds. With a 400mm lens, even on a 50D, it's too far to get anywhere near filling the frame with a single bird and I don't bother with flocks, birds on the ground or (with a few exceptions) in the water. Might as well leave the camera at home :(

What is the point in only opening from 09:30 to 17:00 in summer? The best light is between 05:00 and 07:00 and then again from 19:00 onwards. The rest of the time the sun is too high for optimum results.
I am with you on not sitting in hides Tim (not that I have an hide within 50 miles of me anyway!). Another thing I am not prepared to do is crawl around in the mud to get shots - I tend to be a walker who takes along a Camera.
Not that I am knocking anyone who puts a lot of effort into getting their shots, they get what they deserve and the best of luck to them.

[wilfredsdad]

Hi - having just moved from Olympus kit to Canon kit for bird photography - possibly I might offer some useful comment.
I started bird photography with an Olympus E510, Sigma 50-500mm, Zuiko 70-300mm, Olympus 1.4 tcon. One of the reasons I chose Olympus was the 2x crop factor. After a lot of effort I came to the conclusion that my high failure rate was not entirely due to my lack of skill. I found that even in reasonable light conditions with birds that weren't too far away I still ended up with a lot of poor results - the main problem being poor focus. The Zuiko was considerably better than the Sigma but then again 300m (even with the 1.4x tc) is still a bit limiting for bird photography.
I am sure that both of those lenses are perfectly good lenses for general photography, possibly sport or aircraft photography, but my experience was that they just weren't up to the demands of bird photography.
It seems to me that the question of the value of the 2x cropping factor has been well discussed above - bottom line seems to be that it offers no real advantage in practical terms. IMHO extra pixels ie pixel density does offer a bit of an advantage (basically for a given size of subject you gather more data) but it does require that noise is well controlled. From my experience with Olympus and Canon I found the 10mp sensor on the Olympus E510 to be much noisier than the 15mp sensor on my new Canon EOS 500D.
As many have said above - what really matter is the lens, and in this area Canon is a long way ahead of Olympus. There is no fixed focus 400 or 500mm lens available for the Olympus - all that is available is a 300mm f2.8 which, no doubt is a fabulous lens, but it costs over £5k. Again IMHO a fixed focus lens of minimum 400mm f5.6 (or a very high quality zoom which goes to 400m) is a basic requirement for bird photography - anything less than that is going to be a struggle.
I contacted Olympus UK to try to point out to them the need for such a lens and asked if they were going to offer one in the near future - they did not respond.
I have also noticed that whilst Canon and Nikon do have a presence at the bird and wildlife fairs, Olympus are conspicuous by the absence.
I think (for what my opinion is worth) what matters most is the lens - and Olympus don't offer what is needed for bird photography and Canon (and I think Nikon) do.
I bought my EOS 500D and a second hand (2 year old) Canon EF 400mm f5.6 USM lens for a bit less than you would have to pay for an Olympus E620 and a Sigma 50-500mm. I have found almost immediately that I get much better results (sharper and less noisy), the focus is lightening fast - even in not such brilliant conditions - and it seems to be more accurate. Further the lens is much lighter than the Sigma - and I have found that also really is a significant factor.
I don't often stick my neck out but if anybody asked me which to chose I would say Canon without doubt - hope this helps, regards Pete

[tjsimonsen]

The subject is the same size. The frame is smaller. That is the more accurate way to look at it. It also happens to be a physical fact.
That, Tim, is how a microscope works as well.

Thomas

EDIT: should have been electron microscope..

[JohnZ]

Terry, What do you think of the pics I have posted on here ? Amazingly they are all 100% crops ! This partially due to the risk of the bird flying away and probably to do with a slight touch of desperation ?
AC/DC, I have measured the pics from Keiths link and they are all the same size. 6 x 4 I believe. For whatever reason the cropped pic, using the 40D, has come out bigger than the other two ?
Tim, Large cropping is in no way a sign of clutching at straws. This is ably demonstrated by Roys pics. Perhaps you would also like to comment on the pics I have posted. Oops sorry you are not in favour of large crops are you. Please do not let your quality objectives drop for goodness sake.

[tdodd]

John, I have no wish to engage in a willy waving contest about people's 100% crops. If you are using a prime lens and a camera with moderate pixel density and shooting stuff that is moving about little, if at all, then you can indeed get very acceptable quality from 100% crops that will get you a decent 800x533 image or thereabouts. I don't have a prime longer than 85mm, so for me with my 100-400 zoom it is far more demanding to produce a razor sharp image from a 50D when viewing at 100%. When attempting BIF, which is my preference, it is even more difficult to get a useable image when viewed at 100%. The reason is not poor equipment, or poor photographic technique (other than being too far from the subject). It is simply that the magnification factors are pushing the boundaries to the extreme.

Back in post #25 I was talking about using 35mm film (or full frame sensors) as a baseline for extrapolating all things photographic, and proposed a 12x8 print as a yardstick for a "reasonable" level of magnification of 8X. Let's call that our "Gold Standard".

I also said that to generate a 12x8 print from a 1.6X crop body was a magnificaction of 13X. Let's call that our "Silver Standard".

Well, if we do the maths for a few cameras, when cropping to 800x533, let's see what we find. We'll need to agree on a monitor resolution density in order to convert from physical pixels to the image display size in inches. I propose 100 pixels per inch, which is close to one of many standards of 96ppi, but makes the maths a little simpler. So, if you carve out 800x533 pixels from an image, any image, it will display on that monitor at 8x5.33 inches. Let's establish that as our new "print" size. For ease goiing forward let's convert that to mm, giving a displayed image size of 203x135mm. Now let's look at what that means in terms of magnification factors when we crop at 100% from various cameras.

30D
Sensor dimensions = 22.5x15mm, 3504x2336 pixels.
A crop of 800x533 from that camera uses an area of the sensor equal to 5.14x3.42mm
The magnification factor to get from that crop to our 8x5.33" display is 39X.
That is 5X greater than our "Gold Standard".

40D
Sensor dimensions = 22.2x14.8mm, 3888x2592 pixels.
A crop of 800x533 from that camera uses an area of the sensor equal to 4.57x2.88mm
The magnification factor to get from that crop to our 8x5.33" display is 44X.
That is 5.5X greater than our "Gold Standard".

50D
Sensor dimensions = 22.3x14.9mm, 4752x3168 pixels.
A crop of 800x533 from that camera uses an area of the sensor equal to 3.75x2.50mm
The magnification factor to get from that crop to our 8x5.33" display is 54X.
That is a whopping 6.75X greater than our "Gold Standard".

1D3
Sensor dimensions = 28.7x18.7mm, 3888x2592 pixels.
A crop of 800x533 from that camera uses an area of the sensor equal to 5.91x3.85mm (That's 2.43X larger in area than an 800x533 crop from a 50D)
The magnification factor to get from that crop to our 8x5.33" display is 34X.
That is 4.25X greater than our "Gold Standard".


So, as you can see, a 100% crop from a 50D is far more punishing/ambitious/demanding than a 100% crop from a 40D, which in turn is more demanding that a 100% crop from a 30D (or 5D2), which is more demanding than a 100% crop from a 1D3. Also, even with the most lenient of those crops, you are still looking at image magnification factors that are over 4X greater than our "Gold Standard".

To put it another way, if a pro quality print requires the input pixels from our captured image to be rendered at 300ppi, and our screen only displays at a resolution of 100ppi, we should be squeezing input pixels from our captured image into our output pixels on the display at a linear reduction factor of 1/3, or 33% if you prefer. Not 100%. i.e. to produce an 8x5.33 print you would ideally want an image, after cropping, of 2400x1600 pixels, not 800x533.

So, at the end of all that, yes, you may be able to get the quality you desire when cropping to 100%, but the higher your sensor pixel density the more demanding (unrealistic?) that becomes, and your keeper rate is likely to fall. If your target is moving, like a BIF, then the challenge is even greater. Scrape by with a zoom lens with slow AF and, well, good luck.

It is for this reason that I find that for BIF I usually get just as much reach from my 1D3 as from my 50D. All that I accomplish by using the 50D is a more accurate capture of any blur/shake/misfocus, plus more pixel level noise. I rarely end up with more useable feather detail. For static subjects that is another matter altogether, but for BIF.....

p.s. - of course, for BIF, you usually want a high shutter speed, and to combat shake/blur at high magnifications you'll need a very high shutter speed, which will necessitate pushing the ISO, which in turn pushes noise. That is why I find 100% BIF crops from my 50D to be generally unsatisfactory. That is not the fault of the camera. That is my fault for having absolutely lunatic expectations for what my gear and I can deliver. Again, slow it all down for waddlers, waders, floaters and perchers and everything becomes so much easier.

To conclude, I attach an example shot yesterday with my 50D and 100-400 lens, handheld at 400mm, 1/1000, f/6.3, 400 ISO, IS on, no edits. I include the full image, a 50% crop and a 100% crop. In my opinion the 100% crop is very unsatisfactory, and really not useable. The 50% crop would be OK, just, with some tweaking, but as a print that image is only good for a 5x3 or thereabouts. I know my focus is well calibrated. I do not use a filter. I used One Shot AF and fired off several frames, in short bursts, and refocused a few times. This is representative of the batch. No absolute duffers, no clear winners. At 100% it is simply not good enough. I really do not think I could have achieved better results if I had used a tripod or continued shooting for a week. Quite simply, a 100% crop, with my gear, is pushing things too far.

EDIT : for kicks I've thrown in another image of the KF, shot a few moments earlier, this time as a full frame and 50% crop only.

[JohnZ]

Tim, I suspect that we are in agreement really and that it is my lack of fieldcraft that lets me down. However I also attempt BIF shots and have, to a degree, a few minor successes as I hope the shots posted demonstrate.
The Kestrel was going like a bat out of hell and should be considered very fortunate but then again none of the birds posted were exactly hanging about !
In the end it is all about what folks regard as an acceptable image ?

[tdodd]

A lovely set there, John. Once in a while I can get a half decent BIF when viewed at 100% but it is very rare. Perhaps it is my lack of BIF skill that is the problem, but I think I'd struggle to get even 1% of my BIF shots as sharp as that, probably nearer 0.1%. I shall continue to practice and maybe one day my "luck" will improve. :)

May I ask which lens you use? I imagine it is not the 1-4 zoom.

[JohnZ]

I use my trusty Canon 400mm f5.6. I also use AI Servo, just in case, if you know what I mean.

[AC/DC]

AC/DC, I have measured the pics from Keiths link and they are all the same size. 6 x 4 I believe. For whatever reason the cropped pic, using the 40D, has come out bigger than the other two ?

I meant the size of the subject. In the photo taken with the 40d, the subject is bigger.

Btw, I really like the hobby and kestrel in flight. Both birds I would love to get a half decent shot of!

[JohnZ]

Thank you very much AC/DC. Very kind of you.

[cab1024]

I would recommend that people consider 35mm as a baseline for making photographic judgements and that instead of working in terms of pixels they work in terms of magnifications from that captured image. e.g. a 35mm frome is 36mmx24mm.

To me, what you are asking here negates your entire argument. The image captured with my 1.6x 40D will give me a larger bird when the full-framed image is blown up to 8x12", than a full-frame 5dii, printed full-frame at 8x12" would with the same lens.

And my bet is, you would be hard pressed to tell any difference in IQ at that enlargement size, assuming good light and the lowest ISOs used. But I could be wrong here as I rarely print anything.

As a corollary, I also think the 40D was the sweet spot for pixel densities in a 1.6x crop. The 50D is too dense, thus too noisy. I love pixel peeping at my 40D images when they are perfect. Love it much less when they are not.

[mrmarklin]

Yes, tdodd your last post is quite astute.

Most correspondents have missed the fact that it's not only the pixel count, but also the size of the pixels that matter, all things being equal, larger pixels are better.

In addition, 4:3 will always be pixel size challenged with regard to FF or other crop cameras. A lot of this is historical, as Olympus' claim to fame in the film world was lightweight 1/2 frame cameras.

I really feel that all this will be moot in a few years. FF will dominate the pro and prosumer cameras. Crop cameras were always intended to be an amateur alternative (at least for Canon) due to price considerations. Now that technology has brought the price of FF into the realm of most of the rest of us, and will soon bring it to all but the most price conscious, cropping won't be a serious consideration. After all, the 5D2 with 21MP must certainly satisfy all but the top professional. When I got my 5D it seemed ridiculously good and why would I want a crop camera? (Keeping in mind the challenged MP cameras of the time way back in early '06!)

In summary, while there now appear to be some advantages in a crop camera, one must look to the long run, and buy lenses accordingly to prepare for FF days ahead. The pixels sizes on all 35mm format cameras will only decrease as counts go up, but advantage: FF.