Image quality: Extender on FF vs crop

Both the 70-200 2.8 II and the 200L are very sharp lenses and are doing fine on either FF or crop. Not sure what Brian was doing with the 60D, but most of his 60D shots are kinda soft..., even on the 200 f/2L at f/4

Check out the 6D vs 70D on the 200 f/2L, at f/4. That's a very good comparison since the 2 cameras have exactly the same pixel count.
Sharpness is virtually the same, even though one's FF, the other's a crop (OK, the 6D is a hair sharper)

http://www.the-digital-picture.com …omp=0&FLIComp=0​&APIComp=3

No, I think that the 70-200 suffers at the 200 end and the addition of the teleconverter is not noticeable. Look how much sharper the lens is on the crop at 135 mm compared to the crop at 200.

Also, the aperture is f2.8 rather than f5.6, you may have that much room to up the ISO or you may not.

Mornnb wrote in post #16783134
I suspect this may be because the resolving power of the 200mm f/2 is much higher than the 70-200mm IS II. It exceeds the resolving power of a 20MP FF sensor and can provide enough resolution for the pixel density of a APS-C sensor! Yet it doesn't seem to suffer a teleconverter well...

A 20mpx FF sensor is much more forgiving than an 20 mpx aps-c sensor, if you look at pictures at 100%. If a lens can resolve to the APS-C needs, it certainly will work quite well on FF. Maybe that is what you saying above?

gabebalazs wrote in post #16783177
Check out the 6D vs 70D on the 200 f/2L, at f/4. That's a very good comparison since the 2 cameras have exactly the same pixel count.
Sharpness is virtually the same, even though one's FF, the other's a crop (OK, the 6D is a hair sharper)

How would you do a 100% sharpness comparison between the two if you use the same focal length? You would have to size one up, or the other down to create the same equivalent crop size.

TeamSpeed wrote in post #16783418
How would you do a 100% sharpness comparison between the two if you use the same focal length? You would have to size one up, or the other down to create the same equivalent crop size.

No, as you probably know, Brian at TDP, and most other review sites, disregard that and they frame both FF and crop identically, shoot the res chart completely filling the frame. Obviously they shoot the crop from a larger distance for the same focal length. They aren't concerned, at least during resolution testing, with reach and crop factor, uprezzing, downrezzing. They just want to see how the camera or lens performs when the res chart completely fills the frame, with identical framing for all cameras.
I know that for many people, especially those of us shooting wildlife reach and upsizing/downsizing does matter, since often we're focal length limited.
But they don't really care about that

Changing distance is much like changing focal lengths then, same thing really, other than differences in perspective, which don't matter when shooting test charts. However if they didn't use live view for focusing, some lenses focus can be a tiny bit off at different distances, so changing distances might cause slightly OOF images.

I have seen some primes that focus great, nearly perfectly at one distance, but then off a bit at a different distance, when using phase detect AF.

I'm sure I've read that they do manual focusing, I presume on a rack

TeamSpeed wrote in post #16783412
A 20mpx FF sensor is much more forgiving than an 20 mpx aps-c sensor, if you look at pictures at 100%. If a lens can resolve to the APS-C needs, it certainly will work quite well on FF. Maybe that is what you saying above?

Sort of. This is a matter of crop vs FF with a tele converter. I'm saying the lens is sharp enough for APS-C but on full frame with a tele converter, it's the tele converter which is the limiting factor. No doubt the tele converter has it's own resolving power limitations.
The 70-200mm IS II is not sharp enough for a 20MP APS-C sensor, the 200mm f/2 apparently is.

The problem is that the only crop sensor TDP tested with the 70-200 2.8 IS II was the 60D, which proved softish even on the 200 f/2L. Consequently, we can't know for sure if it was the lens or the 60D body that caused the softness (or a combination) but we can at least speculate based on the 60D's performance (not very good) with one of the sharpest lenses on Earth. I'm sure the 70D or T4i, which both performed much better on the 200L than the 60D, would yield better, sharper results on the 70-200 II, but we may never know since they were not tested on it, and likely will never be.

Take a look at the comparison on the previous page with the Sigma 150-500mm. There does not appear to be much of a difference between crop and full frame+teleconverter.

No, there isn't. A crop + lens is indeed close to FF + lens + 1.4x tc.
And then if you step it up, crop + lens + 1.4x tc is very close to FF + lens +2 x TC, just like my test photos show on the previous page.

But then you can't really step the FF further to the next level, while you can do a crop + lens + 2x tc, which will surpass the FF + lens + 2x TC combo, shot from the same spot.

Here is a 100% crop comparison; again, same exact mp count for both cameras: