Pixel Density / Pixel Size Question

AJSJones wrote:
<SNIP> The total number of pixels captured by the three cameras is different (8, 12 and 22) but the amount of detail that can be made out on the bird's feathers is the same for the 8 and 22 and it's more than from the 12. That's all I'm saying.

BTBeilke wrote:
<SNIP>For the record, I'm not trying to diminish the 20D at all. That may very well be the camera that I end up buying. I just want to make sure I understand the sensor technology independent of the camera as best I can. In the past I've read discussions about a 12-16MP APS sensor where everyone was concerned about noise and image quality due to the small pixels and higher pixel density. Recently, it seems like a lot of 20D users/proponents are singing a vastly different tune and I'd just like to cut through the smoke and get to the facts.

Thanks for the discussion!

AJSJones wrote:
Thanks Jerry, very helpful, not!

The original post asked for enlightenment for a specific set of assumptions. Not for a blanket statement as to which is "better"!

Since then some other conditions have been discussed, so the meaning of a "Which is better?" question isn't so obvious!

From the original post, where the assumption was that the composition is the same (because the cameras use different lenses), the 12MP option is clearly capturing more details than the 8MP option - in that sense it is "better". That was already accepted in the 3rd post

The enlightenment was around the issue of when you can't fill the frame with your longest lens with the 1.6 camera (common with photography of small critters). In that case, the 8MP option is "better" because - if you can't fill the frame of a 1.6 you surely can't fill the frame of a FF camera - the assumption (about equal framing) breaks down.

BTB - folks who feel the film analogy is relevant to a "detail" discussion are familiar with the concept of fine-grain ( dense pixel spacing) and coarse grain (large pixel spacing) films. When I scan my film (Provia100F) at 2500 ppi, I don't see grain to any significant extent. When I scanned NPS160, a Fuji wide dynamic range negative color film, it's terribly grainy and I can't print it as large without the grain being very evident, compared to the Provia at the same enlargement. In any case, it was "only" an analogy and certainly noise plays a role in measurements of resolution as do MTFs etc.

BTB said:
"Now, if you can't use a longer lens or get closer to the subject, the reverse would be true. You'd end up with more pixels on the subject (more detail) with the 20D than you would with the 5D due to the 20D's 1.6x crop factor. But that is a far different issue than saying that the 20D sensor has some inherent detail advantage over the 5D. That is a 1.6x crop factor advantage, not a sensor technology advantage."

I am indeed saying that the 20D sensor has some inherent detail advantage over the sensor in the 5D, because it has a higher pixel density, linear resolution, Nyquist frequency (however you want to name it). This is referring to the "quality" not "quantity" of the details. Look at the central 10mm by 10mm of the 20D, the 5D and the mythical 1Ds3 (the one which has 22MP in a FF sensor) when e.g. a 500 mm lens is focused on a small bird, whose image falling on the sensor is 9mm high. The 20D and "1Ds3" will produce an image of the bird that is 1400 pixels high, while the 5D image is 1100 pixels high. (In terms of data collection - I recently retired from biophysics and spectroscopy so I'm there - this is substantially higher density data, so finer detail is recorded) This is *solely* due to the pixel spacing and *nothing* to do with the format or crop factor. The total number of pixels captured by the three cameras is different (8, 12 and 22) but the amount of detail that can be made out on the bird's feathers is the same for the 8 and 22 and it's more than from the 12. That's all I'm saying.

AJSJones wrote:
All other things being equal, a larger or higher photon capacity, sensor element will have better noise characteristics and therefore a larger dynamic range. If that was your question initally, there'd have been no discussion I don't think anyone said the 20D pixels were "better" than those in the upcoming 5D, they've said the 20D sensor has higher linear resolution than their expectation of that from the 5D (or other sensors with wider pixel spacing) and that they like that. I do and it has practical consequences. I don't think we're in disagreement, are we?