5d3 F8 focusing

Posted this on FM also. Tried my 5d3, with a taped kekno 300 dg 1.4x. here are my thoughts
I went out and tried the 100-400L with a taped 1.4x tc. I tried it indoors, as well as in decent light outdoors.
For non stationary objects, the focusing is good and accurate. a little slow, but over all not bad. overall much better than both my 5d2 and 7D with TC. Spot focus also works.
Here they are, at reported f stop of 7.1 (f10), iso 1600,

very nice!

Not bad, I never really tried the tape trick but might give it a go on my 600L. I was really hoping that the 5DIII would be able to handle the 600L with a 2x multiplier, but I think that brings it above the threshold where autofocus would work. I did try it with a 5DII and it was no go. Manual focusing a 600L with 2x multiplier is really difficult and you have to have one heck of a solid heavy tripod. Does anyone know if a 1.4x would work on a 600L ... not sure what the f stop would be but am guessing around f5.6

I don't understand why Canon doesn't have an option where you can turn auto focus on if it can work with some tape. I think a lot of people would accept non stellar functionality if they are told the limitations.

by the way, the images definitely look better on my computer. flickr compression I guess.

Thanks for posting this.

I had somewhat erratic results using the 300/2.8, Canon 2X TC, and Canon 1.4X TC stacked. It would focus, but it was very erratic and would hunt rapidly before settling down with that combination. Not quite as good as the 5D2's center AF point, but better than the 7D which was very unreliable in this situation.

Here's a shot I took the other day with that combination...

Tom,

please report back on when you try that Kenko TC.

Will do, Rick. My intent is to try/use the Kenko on the 100-400L. It would certainly make for a relatively light walkabout lens setup if it works well.

Excellent. Now we just have to wait for Canon to update the firmware....

spear wrote in post #14212662
I don't understand why Canon doesn't have an option where you can turn auto focus on if it can work with some tape. I think a lot of people would accept non stellar functionality if they are told the limitations.

Purely PR - bunch of people will be all over internet screaming how bad is Canon autofocus (if used with 600 mm/f8)