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Autofocus problem EOS 6D Mark II and EF 100-400mm

tgo2002
Contributor

I have recently-purchased 6D Mark II camera and EF 100-400mm 1:4.5-5.6 L IS II lens.  The past few days the lens will not autofocus at 400mm some of the time.  If I zoom out to 250mm, focus, then zoom back to 400mm, it will focus.  I can re-create the problem easily on the 6D, but on my older 5D Mark III the lens works perfectly.

Has anyone else experienced this?  Is it a problem with the camera or the lens?

1 ACCEPTED SOLUTION

"Lens drive when AF impossible" was set to "Stop."  I switched to "Continue" and it seems to be working inside tonight.  I will try it in daylight tomorrow before declaring victory, but that might have taken care of it.

For what it is worth, the 5D was set on "Continue."

View solution in original post

16 REPLIES 16

Sorry I didn't spell out 6D Mark II both times.  I have that and the 5D Mark III.

Both of those cameras CAN focus at F/8. I would check the setting called "Lens Drive When AF Impossible". To see if the camera will keep searching for focus instead of stopping.


-Demetrius

Current Gear: EOS 5D Mark IV, EF 16-35mm F/2.8L USM, EF 24-70mm F/2.8L USM, EF 70-200mm F/2.8L IS III USM, EF 50mm F/1.8 STM, EF 85mm F/1.8 USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D

No filters, no teleconverter/extender.  The max aperture on the lens is 5.6.  I thought maybe low light would make a difference, but it happened today in daylight.

What about the subject's contrast. Your camera relies on CONTRAST to work NOT how bright it is. No first party Canon EF or EF-S lens has EVER had an aperture SMALLER than F/5.6 early lenses had wider open apertures. They were not smaller than F/4.5 but once they figured out that an aperture of F/5.6 provided enough light and contrast to the AF system. That allowed them to make cheaper and smaller lenses.


-Demetrius

Current Gear: EOS 5D Mark IV, EF 16-35mm F/2.8L USM, EF 24-70mm F/2.8L USM, EF 70-200mm F/2.8L IS III USM, EF 50mm F/1.8 STM, EF 85mm F/1.8 USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D

"Lens drive when AF impossible" was set to "Stop."  I switched to "Continue" and it seems to be working inside tonight.  I will try it in daylight tomorrow before declaring victory, but that might have taken care of it.

For what it is worth, the 5D was set on "Continue."

Older Telephoto and Super Telephoto lenses would often get lost and hunt if the camera couldn't lock focus. I had that problem when borrowing my friend's dad original EF 300mm F/2.8L USM (released in 1987) lens while using it on my old EOS 40D. That was Canon's first lens to feature a Ring Type USM AF. It also utilized focus by wire. This was before Canon had designed a clutch override system found in newer Ring Type USM lenses. 


-Demetrius

Current Gear: EOS 5D Mark IV, EF 16-35mm F/2.8L USM, EF 24-70mm F/2.8L USM, EF 70-200mm F/2.8L IS III USM, EF 50mm F/1.8 STM, EF 85mm F/1.8 USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D


@tgo2002 wrote:

"Lens drive when AF impossible" was set to "Stop."  I switched to "Continue" and it seems to be working inside tonight.  I will try it in daylight tomorrow before declaring victory, but that might have taken care of it.

For what it is worth, the 5D was set on "Continue."


Whenever there are two devices that should function the same but don't it is important to look for differences. You found one. Are the AF modes the same? Typically a mountain range is an easy subject for One Shot AF with single center point. Good contrast between the mountain and the sky. 

John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, Pixma TR8620a, LR Classic
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