EF 70-200 f/4 L & 1.4x Extender - Soft at f/5.6?

[sdemetre]

Hi everyone,

 

I used my 70-200mm with the 1.4x extender (canon) on my MKIII for the first time last week-end and

noticed that images taken at f/5.6 were noticeably softer than at smaller apertures. The lens also seems to

be front-focusing with the extender, whereas it usually nails focus without it. Has anyone had a similar

experience or could shed some light on this? Many thanks!

[thomas_brabant1]

Do you mean soft at 5.6 aperture setting, which would be f8 with TC? Or wide open at f4, which would go to f5.6 with TC? I recently bought a canon 1.4 TC for use with my 70-200. But because I think I have read that 70-200 holds sharpness better with a TC a stop or two down, that's the way I have been using it. I'll have to try some test shots. Be interesting to see your other responses.

 

Tom

[ed_hurst]

Regarding general sharpness, try to use your lens stopped down about 2 stops - which with this lens will be f11. Using it at f5.6 is wide open once you have the converter on.

 

Regarding front focusing problems - can't help you there.

[sdemetre]

Thomas - I was shooting wide open at f4 (f5.6 with the TC). Stopping down definitely

produced sharper images. Thanks for responding. Cheers, S Demetre

[cnhoff]

On my 70-200 i have noticed a visible decrease in sharpness and increase in chromatic aberations with TC wide-open; stopping down one stop to f/8 got rid of both.

[mendel_leisk]

Have you tried shooting a focus test target?