70-200mm f4L IS better than 70-200mm f2.8L IS?

And I'm referring to the 1st generation 70-200mm f2.8L IS, not the new II version.

Looking at this lens test page
http://www.the-digital-picture.com …omp=0&FLIComp=0​&APIComp=4

...the f4 version sure looks as good, and in many cases better, than the f2.8 version at any aperture 4.0 smaller.

Am I missing something here or is the f4 version a better lens (at f4 and smaller of course)?

yes, hands down. the new 2.8 is maybe better, or at least the same, with a useable extra stop. but the size/weight is substantial.

but you're original question is the 4IS is sharper.

True story.

When you need 2.8 its not.

I bet the majority on this site cant tell both apart when they both are @ f4 or beyond...

The f4 is sharper than the 2.8 when wide open,.. but hey, the f4 cant do 2.8,,,

Depend on what you mean by better, if you need f2.8 it is better than the f4

So Ive been told, but I have always thought my 70-200 2.8 IS was SUPER sharp. I am however considering selling it anyway to upgrade to the Mark II.

All of the 70-200 L's are sharp. As already stated, I doubt that most users could tell the difference in real world usage. I'd buy one based on budget and needs, not on sharpness.

Good point. There are photos of test patterns and then there is real photography. If I bought today, I think it would be 70-200mm f4L IS. Another $1000 or so days I don't need f2.8 THAT bad.

Yep, all depends if one needs an extra stop. When I get my telephoto, it will definitely be f/2.8 due to need for extra light. But before I had f/4 version, and it was tack sharp as well.

Its an interesting point, since bumping the ISO up a stop will compensate for the 2.8->4 difference. Ah but what if you want a 1.4x extender? Get a 18MP sensor and crop! LOL!. I love my 2.8, but... sometimes... I wonder if a lighter(ish) smaller(ish) lens wouldn't be more... sensible.

adamwynne wrote in post #10710434
Its an interesting point, since bumping the ISO up a stop will compensate for the 2.8->4 difference. Ah but what if you want a 1.4x extender? Get a 18MP sensor and crop! LOL!. I love my 2.8, but... sometimes... I wonder if a lighter(ish) smaller(ish) lens wouldn't be more... sensible.

Question about the extender. I know almost nothing about these except that in some setups they work and in some they do not.

I have a 50D. If I bought either of the 70-200's mentioned here, would an extender work? Which one?

canons extenders work with all of the 70-200s. skip the 2x, but the 1.4II is very good. another reason I got the 2.8II was to lose my 300 f4IS, which was never carried on a whim. with a good 2.8 and that extender, I'm at 280 f4 and IS. damn close, and all I have to carry is something smaller than the size and weight of a 50 1.8 (never had one, but I'm guessing).

an f4 70-200 gets you a 5.6 280. kinda lame.

those are all full frame numbers. the 200 becomes 320 and with 1.4 becomes 448. I guess a f5.6 448 isn't bad.

F/2.8 lets twice the amount of light hit the sensor that F4 does.
TWICE

I think we know that.

But what that means to one person is different than the next. For some, its action-stopping sports. I couldn't care less. For me, its a shallower depth of field. I don't think the hand-holdability in dim light is much different -- the weight of the 2.8 make it tougher. At f4, the 4IS is better than the 2.8. Better IQ. Also better at infinity focus at 200mm.

ASIDE:
I think another good question would be is the extra stop on the 4IS and 2.8II(IS) worth the extra bulk and weight. Yeah, yeah, TWICE the light-- but again, that means different things to different shooters. I'm sure sports shooters love it. But I'm not sure the stop of isolation (depth of field reduction) is worth it. I never used to question bringing the f4IS, now that I have the 2.8II, I do.