What would you choose? f/2.8 or 400mm

photozone.de used to publish tests of the various Canon 70-200mm lenses with a Canon 1.4x telextender...generall​y there was a loss of about 10% in MTF scores. Unfortunately the tests no longer do this, so we have to rely only upon verbal lore...

70-200mm f/4L at 90% MTF ≈ 100-400 MTF

Tommy1957 wrote in post #15950750
I have a Sigma 70-200 f/2.8 OS HSM and 100-400L. Completely different lenses for different purposes. I also challenge your assertion that the 70-200 II w/1.4x TC is sharper at f/5.6 & 300mm than the 100-400L. Post some evidence, please.

I did provide evidence in the first post.

http://www.the-digital-picture.com …omp=0&FLIComp=5​&APIComp=0

Though I do know one picture does not equal the absolute truth, which is why I asked people if it seemed accurate to those who owned the lenses.

As far as the lens being completely different purposes, that may be so, but for the last 4 years I have been using the 70-200 as my only tele for wildlife... So to me, they would have the exact same purposes. I guess if I ended up keeping both, the 70-200 would only be used for indoor events... I don't go to many of them.

Hulka wrote in post #15951271
sorry better overall at 400.

My turn!

Better at shooting what type of shots?

I have a Canon 70-200 f/2.8 L and 100-400L. I use the 2.8L more because of the aperture and glass.