« on: December 28, 2014, 05:09:52 PM »
I agree that smaller pixels can resolve more detail if the lens has sufficient resolving power.It is funny I have been saying this same thing for years, nearly 7, when I first compared the 7D to the 1Ds MkIII and I used to get no end of crap for saying it. Probably the most vocal maths oriented poster here used to crucify me, he was a 7D owner and insisted that his camera had vastly more 'resolution' than mine, he has since got a 5D MkIII and done the tests, guess what? His estimation of the crop cameras 'resolution advantage' has gone from >60% to around 15% at best on manual focus bench tests.
You are taking so many things I've said way out of context there, it's unbelievable. First, I've never said the 7D had a mere 15% advantage over the 5D III. I did say it might be about 25% on average for the average use case (i.e. no tripod, less than ideal focus, etc.) The 60% statement was qualified with the fact that ignores the bayer array or AA filter...i.e. it's the raw, monochrome mathematical advantage of the 7D's pixel size.
I believe under more ideal conditions, the 7D can realize about a 45% advantage over the 5D III. That is just a resolving power advantage, which when were talking about micrometer sized pixels, isn't something that jumps out of the screen at you...that would be something more like a 200% or 300% advantage, which at the moment only small form factor sensors have with 1.0-1.2 micron pixels.
You and I see different things, which is why subjective comparisons are useless. Maybe I sit closer to my screen than you do, who knows. I see the advantage of the 7D, you do not. Neither of us is right until someone actually does a proper test with proper testing tools and gets some actual resolution numbers. However we all know how well real numbers go down here on these forums as well...so again, it's all entirely pointless.
Simple fact: smaller pixels resolve more detail. I think that has been demonstrated thoroughly well over the last decade, throughout the continual march towards ever smaller pixels paired with frequently improving optics.
In practice, does pixel size affect low light performance for the same sensor area?
By "for the same sensor area", I assume you mean when your subject fills the same absolute area of sensor (i.e. you would need to crop the FF to get the same FoV as the APS-C). In that case, the pixel size isn't really going to affect things much. Assuming same lens, same aperture (which would be necessary for identical subject size and DoF at the sensor), then your going to gather the same amount of light in total for your subject, regardless of which sensor you use. The FF could have bigger pixels, or it could have the same size pixels as the APS-C. The pixel size doesn't really matter...it's just an arbitrary factor. In the end, for an APS-C sized crop of an FF sensor, you gathered the same amount of light as the APS-C itself. Therefor, noise should be the same once the results are normalized. If the FF has the same pixel size as the APS-C, then simply cropping would be enough to normalize. If the FF had larger pixels than the APS-C, then downsampling the APS-C to the same image dimensions as the FF would average pixel data together, resulting in the same noise.
Now, if you framed the subject the same with both cameras, and used the same aperture with both, then the FF camera, regardless of pixel size, is going to perform better.
Pixel size, ultimately, affects resolving power. Smaller pixels, higher resolving power. If you move from an FF sensor with 10 micron pixels to an FF sensor with 5 micron pixels, your going to resolve more detail. Strait out of camera, the image made with smaller pixels will appear noisier...unless you downsample it to the same dimensions as the 10 micron image. Then noise will appear the same, however the 5 micron image will still be sharper and more detailed.
Smaller pixels, assuming same or better technology, can never be a bad thing. On a normalized basis, smaller pixels mean more detail (all else being equal.)