Originally posted by Rondec I guess I sort of agree and disagree with you, Marc. There are definitely differences in image quality between cameras and they show up in differerent situations where cameras are stressed. If you state up front that you are only going to use your camera for shooting web photos, will only shoot iso 100-800, and will never crop, then any camera with more than about 3 megapixels will suffice.
I'd say this is a reasonable assessment, although I think one can go *a bit* further without inviting too much dissent.
As far as resolution goes, we can actually go quite a bit farther. 3MP is already more than sufficient for printing 4x6" at 300dpi, so even at 3MP it is not *just* about web viewing. And if you have at least 6-8 MP (which is to say, virtually all DSLR's made over the last several years), you've got enough pixels that one would really struggle to tell any difference in terms of resolution when printing an uncropped image up to 8.5x11" (the largest most can generally print at home). Those same 6-8 MP also give you room to do a fair bit of cropping on pictures that will be viewed on the web or printed only 4x6".
So with most modern DSLR's, it's really only pictures printed 8.5x11" that are *also* cropped heavily, or pictures printed much larger than that, where there would be likely to be a noticeable difference, at least when it comes to resolution. Differences in color rendering and so forth tend to be much more subjective, and also easily affected by choice of WB or other in-camera settings, as well as choice of PP methodology. While I won't deny that those intimately familiar with their own cameras and their own particular PP methodology can often tell the difference between cameras in their own images, it really becomes pretty hopelessly subjective trying to claim one camera has "better" IQ than another based on these "intangibles".
That's all assuming relatively low ISO. As ISO levels get higher, differences are indeed going to be more noticeable. But even at ISO 1600 it's still the case that viewed at screen size or in 4x6" prints, the difference between the K-x (Pentax's best high ISO camera) and K10D (their worst) is fairly small to my eyes. If anyone wants to see for themselves, check out the K-x and K10D "comparometer" images for ISO 1600:
http://75.126.132.154/PRODS/KX/FULLRES/KXhSLI01600_NR2D.JPG http://75.126.132.154/PRODS/K10D/FULLRES/K10DhSLI1600.JPG
The difference is clear enough in these images when viewing at 100%, but try or viewing them full screen or printing at 4x6". Especially considering that these are just default JPEG's, and that even five seconds spent applying an NR preset in your favorite PP program would be likely to lessen the difference, I'm guessing you could print close to 8x10" and many people wouldn't spot much difference. Of course, we are now getting to territory where more and more people *would* be able to tell. No doubt, when we push to the extremes - high ISO, larger print/view sizes - differences become increasingly obvious. Really, the only question is *how* far we have to push things before the differences become visible enough to any given person.
So despite all the bickering in this thread, I still think these are worthwhile issues to discuss and to try to put in real world context. Was my original statement unnecessarily provocative? Apparently so :-). But if it leads to a more in depth discussion of the issues, I'm OK with that.