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pixel size vs. sensor size

Charles Stobbs , Nov 27, 2012; 10:25 a.m.

I am just starting to use a digital camera almost exclusively and realize how lirtle I know. My camera has an APS-C size sensor but I notice that different cameras with that sensor may advertise different numbers of megapixels. Does that mean they have different size pixels and do printers size the dots accordingly?

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Andrew Rodney , Nov 27, 2012; 10:38 a.m.

Yes, the pixel size can vary quite a bit between camera systems (and to some degree, bigger is better). The medium format digital backs are an example where number of MP's alone doesn't tell us about image quality.
Printers too have varying sizes of dots they can produce.

Keith Reeder , Nov 27, 2012; 12:25 p.m.

(and to some degree, bigger is better)

Only - maybe - in terms of DR (although it's a huuuuge "maybe" - I'll have my 7D's DR over that of my old 30D every time; and I'd certainly want the Nikon D7000's DR over that of my old D70), but in any other meaningful respect not only are bigger pixels not necessarily "better" than smaller pixels, but in some respects they're demonstrably worse.

Other things being equal, there's definitely no overt noise advantage to large pixels (again, 7D over 30D every time - more noise per pixel is irrelevant when averaged across the whole image, and at the image level small pixel sensors are often cleaner); and in terms of micro contrast and detail I'll have lots of small pixels over fewer big 'uns, every day of the week.

Lots of small pixels are better for cropping/pixels per duck at any given sensor size too.

Come to think of it, I can't think of one single metric for which larger pixels demonstrably, routinely, provide a benefit over smaller pixels, at any given state of the art...

Andrew Rodney , Nov 27, 2012; 01:25 p.m.

Only - maybe - in terms of DR

That's a huge influence in image quality! The larger the pixel on the sensor, the more sensitive.
http://www.luminous-landscape.com/essays/sensor-design.shtml

In summary, if you try for ever higher resolution in a small chip – something's gotta give. The smaller the pixels, the lower the quality as compared to a similar sensor with larger pixels. Very small pixels (sub 5 micron) start to run into the laws of physics, where signal to noise ratio, and the simple ability to capture enough photons limits their ability to sustain significant improvements given known technologies.

-----

Come to think of it, I can't think of one single metric for which larger pixels demonstrably, routinely, provide a benefit over smaller pixels, at any given state of the art...

Again, the larger the sensor's pixel, the more sensitive it is compared to the same number of pixels on a smaller chip. That isn't to say the smaller sensor isn't newer and has better processing capabilities etc. If we stick to apple to apples comparisons that is:
http://www.clarkvision.com/articles/does.pixel.size.matter2/

A small pixel can not collect as much light as a large pixel, much like different sized buckets in a rain storm: the large bucket collects more water. But how much? For the range of cameras tested so far, that range amounts to a factor of about 16.

The number of photons a digital camera collects in each pixel is directly related to the size (area that converts photons into electrons) of the pixel and the lens feeding light to those pixels. The more photons collected, the better the signal-to-noise ratio in the image, thus the larger pixel sizes using larger lenses do better in this regard.

Charles Stobbs , Nov 27, 2012; 08:35 p.m.

What I'm really wondering is will all prints from APS-C sensors be the same size regrdless of the cameras megpixel specs, either a lot of small dots or fewer big dots? (asuming I haven't done any up or down rezzing)

Andrew Rodney , Nov 27, 2012; 08:37 p.m.

What I'm really wondering is will all prints from APS-C sensors be the same size regrdless of the cameras megpixel specs, either a lot of small dots or fewer big dots?

In a word, no.

Tim Lookingbill , Nov 27, 2012; 09:37 p.m.

This thread may quell your concerns about camera resolution vs printer...

http://photo.net/beginner-photography-questions-forum/00acnx

Rob Bernhard , Nov 27, 2012; 10:12 p.m.

Charles,

Print size is a function of the pixel dimensions of the input image. It does not matter if the sensor is small or large. If, for two sensors, the total number of pixels in both directions is the same, then the image size, printed at the same dpi, will be the same.

This is different than discussing the /quality/ of the output. Images can be printed large or small from a variety of sources. How big you print depends on the /quality/ of the image and the complexity (detail) of the subject matter. A secondary issue is the viewing distance. If you expect your images to be viewed from a few inches away, then you would want as much detail as possible. If your images are being viewed from a 65mph car on a highway, detail is less of an issue.

Dave Luttmann , Dec 06, 2012; 09:38 a.m.

Well, I'm not one for Clarevison...nor the LL (Remember, the D30 outresolves 35mm film). On a spec sheet, for measurebators, larger pixels matter. In the real world, where things are reduced to the great equalizer (print) it rarely matters. In fact, the highest DR and lowest noise cameras aren't MF.

Andrew Rodney , Dec 06, 2012; 10:21 a.m.

Well, I'm not one for Clarevison...nor the LL (Remember, the D30 outresolves 35mm film).

You mean:
http://www.luminous-landscape.com/reviews/cameras/d30/d30_vs_film.shtml
Specifically, what's your disagreement with the findings of this article?

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