6D AF at f/8 masquerading as f/5.6

Started Jan 5, 2013 | Discussions thread
OP John Sheehy Forum Pro • Posts: 18,856
Re: 6D AF at f/8 masquerading as f/5.6

Richard wrote:

How does the image quality hold up with this combination John?

Sorry for the delay; I thought I responded already.  I typed the post - I guess I never sent it.

My 300/4L IS has a problem with the IS; focus breathes while it is enabled, and it really needs to be repaired.  It is not as sharp as it could be, and displays more lateral CA than it should, so results at 2x are not stellar at the pixel level at wide apertures.

I just tried my 100-400L IS with a single Kenko 1.4x indoors with the CFL lighting, by taping the three pins on the lens, and it works better than the 300/4L (focus is snappier, and results sharper); I think I may be able to use this combo outdoors.  Within the next several days I should have a day out with the combo.  I hate having Exif info that doesn't tell you if you had the TC, though.  Maybe I'll have to get a DGX

I tried taping the 100-400 with the Canon 2x III but it was a no-go; even pointing the lens at the bulb itself, it could not focus, and always quickly overshot focus.  Quite a difference between f/8 and f/11!.  Live View contrast-detect AF worked very well with 800mm f/11.

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