“Full Frame Equivalence” and Why It Doesn’t Matter
Bullshit reasons for FF.
Higher resolution – not true except for the D800.
Sharper – this is only true out of camera with default parameters. Bump up the sharpening a bit on crop and there’s no difference.
Color rendition – with the exception of high ISO, pretty much all FF, crop, and 4/3 sensors are the same here. Your choices with camera settings and/or RAW conversion make the difference.
DoF “control” – FF gives more shallow DoF, but this doesn’t equate to better or “more control.” Crop gives more DoF for a given aperture, which means you can more easily shoot wide open for the light gathering or for blur in the background. (Blur near the plane of focus is determined by DoF. Blur well behind the plane of focus is determined by physical aperture size and is the same regardless of format. If you want a model’s entire face to be sharp but the background to be smooth, it’s easier to achieve on crop.)
I find fast primes to be too shallow on full frame, and always end up stopping down thereby losing light and some background blur (unless the model is very near the background).
Real reasons for FF.
If you need to shoot above 6400, FF kicks ass over crop.
There are some fast, wide primes and T/S lenses with no real equivalents (for the FoV) on crop.
If you can’t afford MF but want the highest possible resolution, the choice right now is a FF body (D800).
FF does yield about a stop more DR.
The very best pro sports bodies are FF, though the crop 7D is quite frankly up to the task of pro sports, at least in decent