Quote Originally Posted by bburns223


Quote Originally Posted by calmars


bburns, the f/2.8 doesn't turn into a f/4.5 just because it's mounted on a 7D. Only with extenders. However I agree with everything else you and everyone have said. The 70-200 is definitely the way to go.



yes, it does. Not only does a crop body multiply focal length by 1.6x, it does the same to effective aperture. I learned that in this thread:


http://community.the-digital-picture.com/forums/p/2861/22988.aspx#22988


About halfway into it it's explained.


brendan



In terms of depth of field, yes - for an identically-framed subject, because to get that framing, you must be further away. Not in terms of light-gathering ability - the sensor does not physically affect the lens, obviously, although a crop sensor only 'sees' a portion of the image circle projected by an EF lens.