Quote Originally Posted by neuroanatomist View Post
It's a true statement, much like it's also true that the moon is made of green cheese. Whoever told you that, I'd recommend doubting them if they said the sky is up or water is wet.

Get the 70-200mm f/4L, budget permitting. Cropping that to the 300mm framing will give much better results. If you actually need more native reach, consider the 70-300L (not the non-L, which is very soft >200mm).
Squidy - I agree w/ Dr. Brain, never go back to who told you the 75-300 was in anyway an option - never - they may engaging and colorful, but either are completely misinformed or worse. The 70-300 much, much better, and the for the $$ the f4 70-200 is perhaps the best lens you can buy.

It is only 1 stop from the 2.8, weights a lot less, and provides nearly identical image quality to the 2.8 at f4 - particularly on crop bodies. at f5.6 there is only a difference for those that over enlarge and then get their noses against the glass of the picture frame.

Think of it this way, the "film" (sensor) on your camera is identical to the 7d, as such it can benefit from all the resolution and contrast any lens can provide. The sensor, can't record what doesn't get it, and if what gets to it is fuzzy so will be the recording. The pros use the best glass they can get... they could save the price differential on a several lenses - not just one at a time but several times, no one has unlimited budgets - if the quality didn't make a difference..... it simply does.