A little question on crop factor (1 Viewer)

baofeng

Well-known member
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.
 

stevetb

Registered user
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.
 

Keith Reeder

Watch the birdie...
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 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.
 
Last edited:

tdodd

Just call me Tim
(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.
 
Last edited:

Keith Reeder

Watch the birdie...
"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

Just call me Tim
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.
 
Last edited:

goodwin912

Member
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
 

stevetb

Registered user
"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

Just call me Tim
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.
 

stevetb

Registered user
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

Hi!
Staff member
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

Occasional bird snapper
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.
 
Last edited:

stevetb

Registered user
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 call me Tim
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.
 
Last edited:

goodwin912

Member
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

Well-known member
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?
 
Last edited:

tdodd

Just call me Tim
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.
 

Attachments

  • 20090723_180033_0480_Neat_LR.jpg
    20090723_180033_0480_Neat_LR.jpg
    36.6 KB · Views: 151
  • 20090723_180033_0480_Neat_LR-2.jpg
    20090723_180033_0480_Neat_LR-2.jpg
    61.2 KB · Views: 201
  • 20090717_085801_0222_LR.jpg
    20090717_085801_0222_LR.jpg
    41.8 KB · Views: 144
  • 20090717_085801_0222_LR-2.jpg
    20090717_085801_0222_LR-2.jpg
    95.5 KB · Views: 156
Last edited:

baofeng

Well-known member
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

Well-known member
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....... ?
 

Users who are viewing this thread

Top