Two very similar lenses, huh?
Tripod, 2sec timer, ISO 100. 200mm.

75-300 4-5.6 III, 1/100th, f/5.6


70-200 (f4 non-IS version), 1/100th, f/5.6


75-300, 1/100th, f/8


70-200, 1/60th, f/8


This really surprises me. The 75-300 seems to be almost as sharp as the 70-200. Especially at f/8, not as much at 5.6.

The 70-200mm, f4L handily beats the 75-300mm, f4-f5.6 when the first is at f4 and the latter is at f5.6. As you say, the latter improves as you stop it down a bit, but look how much light gathering you lose. 2 stops is an efficiency factor of 4. Plus you lose some DOF control if you have to constantly stop down just to achieve "acceptable" sharpness.

That's the true value of the very expensive lenses like the Canon "L" lineup.

Exactly. But if you're always at f8 (although I have no idea who would be doing that in this range) then you might want to consider the cheaper option...

Originally Posted by ThatCanonGuy Exactly. But if you're always at f8 (although I have no idea who would be doing that in this range) then you might want to consider the cheaper option...

Interesting. I remember when I bought my 70-300 that the 75-300 was being bad-mouthed all over the place.

Looks like the 70-200 does a much better job with the colors.

Originally Posted by ThatCanonGuy This really surprises me. The 75-300 seems to be almost as sharp as the 70-200. Especially at f/8, not as much at 5.6.

Ummm .... not so much. Take a closer look at your corners and the bottom of the trunk. Even at f/8 and at this size image, there's a world of difference to be seen there.

This is weird. I had the 75-300 III from canon(non IS) and it was a truly horrid lens.
Maybe you got a rare good copy. I had to stop down to F9 to get decent stuff. even at F8 it was not sharp enough.

Originally Posted by Scott_Quier Ummm .... not so much. Take a closer look at your corners and the bottom of the trunk. Even at f/8 and at this size image, there's a world of difference to be seen there.

Agree. the detail from the L lens is really quite obvious, especially in the bark of the tree. And I am not saying that because I own the L lens.

Frankly, the reason the L is so much better is consistency: even after all these years, I am often surprised at how sharp and detailed shots are with it. It is the best price/performance lens in the Canon line-up.

Originally Posted by ThatCanonGuy Exactly. But if you're always at f8 (although I have no idea who would be doing that in this range) then you might want to consider the cheaper option...

First, to my eye, your shots show the 70-200 to be noticeably sharper and better in all respects. They are not close. Take a better, more critical look at them. Two, even if you shoot at f/8 there are good reasons to have faster glass. Your camera always meters and focuses wide-open, only stepping down the aperture when you press the shutter button. So faster glass lets in more light during the crucial steps of metering exposure and setting auto-focus. More light equals more data equals more accurate focusing and metering of your scene. It also helps immensely in low-light shooting (even if shooting at f/8).

Good points, I now notice how different the corners look. I wasn't saying that I'd rather have the 75-300 for the value (I love my 70-200) but just that it's closer than I expected.

Originally Posted by ThatCanonGuy Good points, I now notice how different the corners look. I wasn't saying that I'd rather have the 75-300 for the value (I love my 70-200) but just that it's closer than I expected.

the difference is even greater on a XXXD or XXD body, especially at the longer focal lengths