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MegaPixels, what's that about????

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Old Wednesday 30th March 2005, 22:35   #1
Mickymouse
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MegaPixels, what's that about????

Both my previous cameras where 2 megapixel and gave good results for general photography, when I loaded them on my PC the images where big enough to have to scroll them all over the place to look at them, my newest one is 3.2 megapixel so I have to scroll even more to look at them, ok so I can reduce the size easy enough for viewing and printing but what is the point in getting all excited about even more megapixels, flummoxed!!!

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Old Thursday 31st March 2005, 06:53   #2
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One of the big advantages of having lots of meggypixels is that you can do a lot of cropping.

If you take a pic of a bird that's a long way off, it may only occupy the middle 20% of the frame. With your 2MP camera that'll mean the bird is imaged by only 400x200 pixels - which will result in either a very small picture on your PC, or a 'blocky' picture, as each of those pixels is expanded in size.

With an 8MP camera that same picture (all other things being equal) will have the bird represented by twice as many pixels - 800x400 - resulting in a clearer, sharper, larger picture.

When it comes to printing meggypixels are even more important. Your monitor only displays about 80 dots per inch. But printers produce many more dots per inch. It's generally reckoned that a good print requires 300 dots per inch, although 150 dpi will do.

So your 2MP image will just about do for a 6x4 print (which really needs 6x300 x 4x300 = 2.16MP). But an 8MP image will be able to produce prints of the same quality that are twice the size - 12x8 inches. Or you can crop the 8MP image and still get a good 6x4.

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Old Thursday 31st March 2005, 20:09   #3
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Thanks for that, I had honestly not noticed any quality difference only that the pictures where bigger and they already seemed plenty big enough to me so I shall go off and experiment.

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Old Friday 1st April 2005, 10:01   #4
iporali
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Mick,

I think you raised a very good question. IMNSHO the trend towards 7-8Mpix point-and-shoot cameras is pure craziness. In theory you have lots of resolution to crop or magnify, but in practice even the lens may not be capable of that - and if the camera has not been perfectly focused and stably supported (on a tripod) those megapixels are completely wasted diskspace. I am afraid that there are many, who always shoot at maximal resolution but never make larger prints than 4x6 (10x13/15cm) - and maybe even don't know how to crop - well, not necessarily on this forum.

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Old Thursday 19th May 2005, 19:17   #5
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Mick,

7MP is overkill. I was quite shocked the other day when I took the attached photo of a swan. I looked at the picture on the PC screen and thought "there's a speck of dirt on this shot". Then I thought, "no, it's a mosquito on the swan's back". Then I looked at the shot at full 1:1 scale 5MP resolution. I found I could count the legs on a mosquito on the back of a swan with a picture taken from about 25 metres away. Just how much more resolution do you need?

Duncan.
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Old Thursday 19th May 2005, 22:16   #6
delia todd
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Quote:
Originally Posted by Yelvertoft
Mick,

7MP is overkill. I was quite shocked the other day when I took the attached photo of a swan. I looked at the picture on the PC screen and thought "there's a speck of dirt on this shot". Then I thought, "no, it's a mosquito on the swan's back". Then I looked at the shot at full 1:1 scale 5MP resolution. I found I could count the legs on a mosquito on the back of a swan with a picture taken from about 25 metres away. Just how much more resolution do you need?

Duncan.
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Old Tuesday 28th June 2005, 21:46   #7
Jay Turberville
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Quote:
Originally Posted by Yelvertoft
Mick,

7MP is overkill. I was quite shocked the other day when I took the attached photo of a swan. I looked at the picture on the PC screen and thought "there's a speck of dirt on this shot". Then I thought, "no, it's a mosquito on the swan's back". Then I looked at the shot at full 1:1 scale 5MP resolution. I found I could count the legs on a mosquito on the back of a swan with a picture taken from about 25 metres away. Just how much more resolution do you need?
.
Need? That's hardly the question. The question is how much do I want. And for me, that's about as much as I can get and afford.

I like making prints. I especially like making big prints. I don't think a camera can deliver too much resolution. I recently bought a 4x5 view camera because I know it will be quite a few years before digital can affordably resolve as much detail. I scan the transparencies at 2400 Dpi and get 90Mp images. I'll also stitch digital images together to get even larger pictures.

Detail and resolution are good things, IMO. 7Mp overkill?!? I don't think so. I want much more.

http://www.jayandwanda.com/birds/cwren_zoom.html

The nice thing about digitals is they almost always allow you to choose shooting in a lower resolution if you prefer. So you lose littlle by having the capability to shoot with a greater resolution.

Of course, everybody has somewhat different needs. If all you do is look at images on your screen, email photos and make the occasional 5x7 or 8x10, then certainly, a 2 or 3mp camera is completely sufficient and perhaps even too much resolution. But from a print quality quality standpoint, you probably need 5Mp or better (conventional sensor design - megapixels to NOT equal resolution BTW) to get print image quality that approaches 35mm film. 3Mp is nice, but it doesn't provide the overall image quality that a good 35mm camera provides.

'm sure there are people chasing after megapixels that won't really benefit from them and consequently they are wasting their money. So for some people, the chase is silly. You just have to define what it is you want to do with your images before you can know.

BTW, its nice that you can count the legs on the mosquito, but by my eyes, that is only because I happen to know to expect six legs. The mosquito is quite indistinct. This level of fuzziness would limit how far this image could be successfully enlarged. Furthermore, mosquitos can easily be over an inch long. So I'm not sure that seeing this mosquito this says a lot about the detail resolved in the image.

The megapixel counts rise much faster than the actual increase in resolution because the megapixel count is an indication of the number of sensors in the picture area. Twice the resolution requires four times the number of pixels (assuming the same sensor design). 7Mp isn't "overkill". Its only a 20% resolution increase over 5Mp.

Personally, I''m waiting for a 10Mp Nikon DSLR at an affordable price. That should serve me well for a number of years. And then, I'd expect even more sensor design evolution and cameras capable of even greater resolution - which would be just fine for me - but not necessarily what everyone should buy.
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Old Wednesday 29th June 2005, 08:49   #8
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my 2 cents....

To get the same amount of results(print-size, i mean), as regular 35mm film,
a digital image needs to be approx 24MP.

With the same print quality, the size of the print of a 12MP D2X image will
be half that from a regular 35mm film. Thats what i believe.
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Old Wednesday 29th June 2005, 11:33   #9
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Quote:
Originally Posted by jobkjoseph
my 2 cents....
To get the same amount of results(print-size, i mean), as regular 35mm film,
a digital image needs to be approx 24MP.

With the same print quality, the size of the print of a 12MP D2X image will
be half that from a regular 35mm film. Thats what i believe.
Maybe, but it depends on how big you want to print. Here's a quote: "If you think that at some point you will want to print one of your photographs at 8 x 10 (which can be nice if you get a real winner), then you just need a 4.0 megapixel camera. Don't let a salesperson tell you that you need more." http://www.digicamguides.com/learn/megapixels.html

I've never printed bigger than 8x10 inches (200x250mm). Most of my prints are postcard sized anyway so 2MP would do most of the time.
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Old Wednesday 29th June 2005, 13:44   #10
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What about different senser designs. In casually reading about the newer DSLRs I seem to remember some saying a good 5mp can yield better results than a cheap 8mp.
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Old Wednesday 29th June 2005, 15:09   #11
Jay Turberville
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Quote:
Originally Posted by jobkjoseph
my 2 cents....

To get the same amount of results(print-size, i mean), as regular 35mm film,
a digital image needs to be approx 24MP.

With the same print quality, the size of the print of a 12MP D2X image will
be half that from a regular 35mm film. Thats what i believe.
That sounds like the conclusion you might reach if you are only looking at resolution figures. In reality, what accounts for image quality is more complex. Noise, for instance, is also an important factor. Digital cameras deliver much lower noise than even the finest grain film cameras. You might want to do some reading here: http://www.normankoren.com/Tutorials/MTF7.html

From a practical standpoint, people generally find that a 6Mp or 8Mp DSLR delivers image quality that it visually the equal or superior to 35mm film images for most photographic circumstances. The DSLRs with 11Mp and above are observed to deliver prints that approach or rival medium format results. There is, of course, some overlap in these numbers since various films have different grain and resolution and digital cameras deliver different results at different ISO settings. But this seems to be the concensus among most professionals and serious amateurs using these cameras. It also jibes with my personal experience. I find that I can make an 11x14 print from my 5Mp CP5000 that looks as good or better than the 11x14 prints I made on an optical enlarger 20 years ago with 35mm Kodachrome. I expect my new7Mp C7070 to do somewhat (but not dramatically) better.
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Last edited by Jay Turberville : Wednesday 29th June 2005 at 21:19.
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Old Wednesday 29th June 2005, 15:17   #12
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Quote:
Originally Posted by RobConnel
What about different senser designs. In casually reading about the newer DSLRs I seem to remember some saying a good 5mp can yield better results than a cheap 8mp.
Its really not even a good idea to use megapixels to refer to resolution. The relationship isn't that direct. Small sensored cameras deliver somewhat less actual detail per megapixel than do DSLRs (for the most part at least) and different sensor designs such as Fuji's Super CCD and the Foveon will deliver more resolution (per x-y cell grid location) and also have different image characteristics than conventiona Bayer mask cameras. Things are actually much more like the situation with computer CPUs. Megahertz does matter, but you shouldn't rely on that alone when evaluating processor performance. Likewise, don't rely on just the megapixel number when evaluating image resolution and quality.

As a case in point, the 7Mp sensor used in the Olympus C7070 seems to be delivering image quality about on par with the larger (physically and by pixel count) 8Mp sensor found in many other cameras. This is counter intuitive, until you realize that the 7Mp sensor is about a 2 year newer design. So it is perhaps better optimized.

My suggestion is to use megapixel counts only as a general guide and to look at the detailed test results if you want to know what the camera is really doing. But this matters only if you plan on doing a lot of printing at 8x10 and larger. Otherwise, just about any modern camera will deliver plenty of resolution and good image quality that will make most people happy.
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