I got a question please guys.
Most photographers I know don't put much stock into the number of megapixels, often citing printing size as the sole benefit.
Is this true? Is there really nothing else to megapixels other than printing size?
The ability to crop is (or can be) a biggie. When I am shooting fast moving sports I often give myself a little extra margin in camera knowing that I can crop it later.
Indeed! And with wildlife, small birds, particularly, cropping gets the shot if you don't have a long enough lens.
This is often said, but rarely backup with proof, mainly because it isn't actually true.
Here is a same generation crop sensor at 100% and a cropped ff sensor upscaled to the same pixel number. Whilst there is a fraction more detail in the 7D image this was a bench test under ideal conditions; using AF, hand holding, higher iso etc, would all level the field. The 7D crop has over twice the pixels the 1Ds MkIII crop has!
Is there a good reason to own a crop camera? Sure, it might have better AF, it is easier to frame as the subject is magnified more in the viewfinder, the image you see is closer to the image you will get etc etc, but there is a mere fraction of difference in actual image resolution and even that small difference isn't realisable in real world shooting.
This argument is flawed on two fronts. First, the same things you claim detract from any benefit the 7D has also apply to the 1D IV. Camera shake, for example can diminish IQ well below the potential for either camera.
Second, and more important...final image resolution is the result a blend of each factor that detracts from initial resolution. Since final image resolution is a convolution of camera shake, AF missfocus, lens aberrations and diffraction AND sensor resolution...the 7D would still come out on top even WITH all of those things affecting IQ. Assuming the same amount of camera shake, AF missfocus, and lens resolution...the only difference between the two then is sensor resolution...and the 7D wins.
First, I am not presenting an argument, I am presenting empirical results of a test.
Second, I used a FF 1Ds MkIII not an APS-H 1D MkIV.
Third, I agree the 7D "wins", though I don't agree with the oversimplified knee jerk rhetoric. I even pointed out in my initial post that the 7D does have more resolution, just nowhere near as much as anybody would guess or expect, most people are pretty emphatic that the far denser sensor of the 7D would trounce the less than half the pixel numbers of the FF, but it just is not so. The 18MP of the 7D equate well to the 36MP of the D800, we all know, as a system, the 5D MkIII at 24MP and the 24-70 f2.8 MkII resolves more, as bench tested, than the D800 and Nikon 24-70 f2.8, 18MP to 15MP.
I know and understand image resolution is a result of system resolution, I just pointed out, with images, the system resolution of an 18MP crop camera is not very much different from a crop from a 21MP FF camera. Again, that is not an argument, it is an empirical observation.