« on: October 19, 2012, 09:00:11 AM »
No crop sensors don't add reach, a 400mm is a 400mm no matter what size sensor it is put on. It will give the same optical effect if you are at the same distance. You will see the difference when you display (print) your images; for instance comparing the 1DX and the 7D, both 18MP sensors. Imagine you take a picture at the same distance with both cameras, subject filling the frame of the 7D. You then crop the 1DX to the same framing. Your photos will look exactly the same, however when you print then out @ 300dpi the 7D will be roughly A3 size the 1DX slighly under A4 (18MP vs 7.2). What if you only print out at A4? You downsize the 7D and upscale the 1DX image a tiny amount, you then have exactly the same image (not accounting for pixel quality).
If your intention is to print and display your image at A3 300dpi, then your 7D requires no upsampling; the 1dX image will require considerable upsampling and will more than likely introduce artifacts which will degrade the overall quality of the image. So the benefit of the 7D over the 1DX is only when displaying images at large sizes like A3 where large scale upsmapling a cropped 1DX image is likley to intorduce unwanted artifacts which would degrade the image to that lower than the 7D (never tried this but would think it would).
Ever seen those beautiful bird portraits with the buttery smooth background taken with a FF and 600mm, you can't do that as well with a crop and 400mm lens at the same (similar) distance (640 effective focal lens). A FF allows you to get closer to the subject and still retain the same framing as crop with shorter lens, therefore the bokeh is far better and is a more desirable quality in photographs which is the benefit of FF with long lenses. I'm not going to mention any more benefits of FF like cleaner files as we all know about that...