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Old Jul 9, 2002, 11:45 AM   #1
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Default little pixels better than big ones?

big pixels vs little pixels:

Call me skeptical!

I have been trying to decide between the a DLR and the Nikon 5700. I see many issues, but finally decided to avoid dSLRs until they either standardize on a physical chip size of produce a full frame 35mm look alike.

However, as I looked into the issue, I began to wonder if there is not some hype out there about existing dSLRs. I am a scientist and, by training skeptical.

For example, the Nikon rep tells me that the D100 is inherently sharper than the 5700 because the chip is larger in the D100.

This does not make sense to me.

any good quality lens should resolve well beyond the physical pixel size at the image plane of either camera. Putting the pixels closer together should, I think, only mean losing resolution IF the circle of confusion of the optics is bigger than the the size of the pixels.

Moreover, assuming that the lens is designed to provide optimal sharpness at its designed image size on the film plane, then, as we all know using only PART of the image, e.g. as in digital zoom, means LOSS of resolution power of the lens! BUT, this is exactly what is done in a D-SLR since the chip covers only part of the image plane.

Frankly, all other things being equal (and I am sure there are other considerations) the 5700 should, IMO give a higher resolution than the D100!

The ideal dSLR may be one built around a SMALL chip! Imagine an SLR the size of the 5700 or even the size of the Oly 20!
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Old Jul 9, 2002, 12:07 PM   #2
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This should answer your question.

http://www.luminous-landscape.com/dq.htm



[Edited on 7-10-2002 by steve]
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Old Jul 9, 2002, 12:51 PM   #3
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"any good quality lens should resolve well beyond the physical pixel size at the image plane of either camera"

That's where AF-S and L series lenses from Nikon and Canon come into play. Compared to ANY lens on fixed lens digital cameras, AF-S and L lenses are sharper, faster, yield more accurate color (not muddy), and much more distortion free (chromatic, pin cushion, barrel, etc). But they ain't cheap at all. Cost vs benefits, you know the rest

And as for sensor dimentions, size does matter. Smaller sensors pack individual pixels much too close to one another compared to larger DSLR ones, which means signals can crosstalk, or interfere causing image noise. Sure there are noise reduction algorithms that can be employed, but it's like treating the symptom and not the disease. Also, with the DSLR's the extra money goes to better algorithms that convert raw data into the images we see. Oviously, the folks at Kyocera must've employed a poor algarithm to convert their full-frame ccd raw data, because the N1 Digital's images look as grainy, if not more so than the images from my E-10. And there's a $6000 gap in price here... Wonder what all that money goes for in the N1 :P It could also be that the Philips ccd used is not that good to begin with, certainly not in the same league as Kodak, Canon or Nikon sensors used in their DSLR's (for their consumer cameras they use smaller Sony ccd's).

[Edited on 7-10-2002 by marokero]
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Old Jul 9, 2002, 2:08 PM   #4
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Another advantage to large CCD size is the physical scale of focal length and aperture. Small CCDs mean small true focal lengths and corresponding small physical aperture sizes. When stopping down a lens you quickly run into diffraction problems not to mention the problems in building the iris that tiny. I like my D7 but the lens only stops down to f9.5. The Oly E-10 and E-10 go a half stop further to f11. Some of my Nikon film lenses stop down to f32 though admittedly the best image quality is at f16-f22.

I can't justify a DSLR yet as there's no way I can amortize the cost before it becomes obsolte. I won't be getting one now but expecet to within a few years. When Nikon has a full frame DLSR with no magnification ratio and 14-16 million pixels it will be much more attractive.
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Old Jul 10, 2002, 12:16 AM   #5
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Sorry but I do not buy into the nose problem with small pixels. Each pixel is a discreet element on the chip, the only reason they would have cross talk is light scatter at the chip level and I assume the engineers can handle that. As long as the circle of confusion is smaller than pixel, I do not see why this would be the case.

The issue of diffraction with shorter FL lenses is more interesting. I really do not know if this is true. Diffraction occurs when an object approaches 100-200 microns (.1-.2 mm). This is a physical limit related to the wave lengths of visible light. and will show up in the size of the circle of confusion ,the smallest object a lens can produce as an image. Even at 5 megapixels, I suspect the circle of confusion is much smaller than a pixel since photography grains are smaller and there are a lot more of them then there are pixels!

The issue of color correction ion more expensive lenses, as with other issues of lens quality, seem to me to be more serious. HOWEVER, at least some of this is given up by having a chip to small to use the full field. Obviously, the smaller the field of view of the chip, the worse the picture for the same reason that digital zoom is a bad idea!
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Old Jul 10, 2002, 10:47 PM   #6
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Light vs electrical noise.

As with any electronic device there will be an inherent amount of electrical noise. Since that cannot be entirely eliminated it comes down to a simple matter of physics that determine the signal to noise ratio.

Less photons will hit a smaller pixel, than a larger one. The photons are equivalent to signal. Less signal for the same amount of noise on a smaller pixel will yeild a lower signal to noise ratio than a CCD with larger pixels.
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Old Jul 10, 2002, 11:02 PM   #7
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Default Just something to think about...

Quote:
Sorry but I do not buy into the nose problem with small pixels.
In the relevant sense, noise is somewhat of a constant while signal is highly variable. Larger photo sites capture more data which enhances the signal to noise ratio thus providing images with less noise.

The primary problem with crowding too many sensor points on the chip is adjacent photosite electrical leakage in high contrast areas causing blooming. The combination of adverse signal to noise ratio and blooming coupled with extremely short true focal lengths create the major disadvantages with consumer grade sensors.

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Old Jul 11, 2002, 2:24 AM   #8
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1. phtons per pixel ...

Obviously the number of photons is less if the pixel is smaller. However, the major effect of this would be on sensitivity. This >>coiuld<< be noise is the electornics used to detect a weaker signal generates more noise. OTOH this would also mean that small sensors would be less sensitive.

Actually , is it true that the pixels are physically larger on the larger chip? or are they more spread out.

2. leakage ... I am nto sure, do the pixels function in an analog or digtial manner? Given the large size of the pixels as compared w9th details in other chips, I am skeptical here too.

It would be very nice to see some real worl resolution tests to answer the question!
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Old Jul 11, 2002, 8:53 AM   #9
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Default More on above...

Quote:
Actually , is it true that the pixels are physically larger on the larger chip? or are they more spread out.
Yes on both counts - the photosites on professional level sensors are "Huge" in comparison to their counterparts in consumer level sensors.


Quote:
It would be very nice to see some real worl resolution tests to answer the question!

I suspect here is where the confusion lies. Absolute "resolution" is determined, in the electrical sense, by nothing more than the pixel count - and in the optical sense, by the lens.

Your rep who told you that sharpness was greater "because of pixel size" was not specific enough. Smaller pixel size would "actually" promote perceived sharpness because of obvious reasons, but the superior noise reduction and greater dynamic range provided by the professional sensor, plus the decrease or elimination of adjacent photosite leakage in high contrast areas (blooming) result in a printed image which appears "sharper" to the human eye because there is less overall visual "noise" to detract from perceived image quality. Perceived sharpness, in the relevant sense, is a product of increased edge awareness accomplished by increasing relative contrast in a small area of pixels bordering edge detail on subject material.

There are numerous examples of these differences on some of the reviews where resolution charts are photographed. Though actual resolution measured in line pairs per mm may be identical or even lower for professional cameras with lower pixel counts - prints from these cameras are significantly better in terms of clarity and perceived sharpness, even though actual "detail" may be better in a consumer camera with a higher pixel count than it's professional counterpart. A good example of this are prints from a Sony DCS-707 versus prints from a Canon EOS-D30. Though the D30 gives up two million pixels to the F707, prints from the D30 are significantly "better" than identical subject prints from photos made by the F707.

The bottom line here is that there is more to the "quality" of a printed image than resolution alone would suggest.

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Old Jul 11, 2002, 10:33 AM   #10
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This reminds me of some of the old debates about Zeiss vs Nikon lenses.

There >>could<< be a variety of reasons why the larger pixel camera woudl be better and I certainly believe fixed zooms can nto equla interchanegeable lenses.

Still, the issues you raise are largely subjective. I would like to see a double blind trial of the 5700 vs. the D100.
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