umut_h_toprak wrote: billsnature wrote:
These samples represent the use case. Shot in AFC as that is how I would use the lens. If it's OOF, that isn't my fault. It showed eye detect. I agree it looks a little front focused if you look at background, but if you look at the stick below the feet that should be sharper as its it's closer to camera, but its not. It appears to have a narrower DOF. Both the foreground and background are sharper in the 400-800.
I shot many frames and have been taking random pairs (not best vs best) and no pair so far has shown the 600 1.4x combo better but I will test many more.
I have no interest in manually focused comparisons as that isn't how I shoot.
I agree with your thoughts and approach except for one aspect: I think you should take the best-vs-best comparisons and also make a mental note of the keeper rate in bursts even for static subjects. This would allow you to compare both peak performance and focus reliability.
Here is the best of 6 shots from 600 with 1.4X vs a new random sample from 400-800 at 800. 400-800 on left and 600 w 1.4X on right. The 400 to 800 is still sharper. Even when scaled to match size. Notice the background sharpness showing greater DOF in 400-800mm in last image.
Possible explanations:
1) I have the best 400-800 ever made (Could be true. It is stellar)
2) f8 vs f9 is a big deal. Seems unlikely that if falls off a cliff like this but possibly
3) I have a bad copy of the 1.4X TC. Very possible, but looks OK on other lenses.
4) I have a bad copy of 600mm f6.3 (I will look harder at 300GM vs 600 to estimate)
5) 600mm f6.3 doesn't take TC well. This was true for 400mm f2.8 and could be true for this lens. The strange DOF difference could be a clue here
I am hoping others can confirm, but my results aren't way different than some YouTube reviews. Might look closer at longer distance.
Oct 16, 2026 at 11:03 AM
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