AFMA - Huge Swing

[eos650]

Hi All,

Yesterday afternoon I shot pictures at a soccer match. One combination 5D Mark III, EF 400mm f2.8L IS II and EF 1.4X III gave me terrible results. Everything was severely back focused. I do AFMA my lens/body combinations occasionally and normally they are spot on.

This body/lens combo AFMA'ed at +9 on 10/7/2014. I didn't bother to re-calibrate it for yesterday's game and I know lenses/bodies change but I wouldn't have expected such a huge change. Today I re-calibrated the body/lens combination and ended up with a -9. That's an 18 point swing. I have done several test shots after re-calibrating and the body/lens combination now appears to be spot on.

What concerns me is the amount of swing. 18 points seems incredibly large. Neither the body or the lenses have been dropped, banged, etc.

The 400mm f2.8L IS II was spot on, on my 1DX during the same game, however I wasn't using the teleconverter in this combination. Also, I shot a bit with the 5DIII and a 70-300mm L, which was also spot on. This leads me to believe that my 1.4X III teleconverter might be the culprit.

Has anyone else here experienced such a huge change in AFMA that wasn't caused by some other event such as dropping a body or lens?

 

[No Mayo]

I assume that you also calibrated the 5d3 with the 400 2.8 without the extender back on 10-07-2014. I suggest that you calibrate the 5d3 and the 400 2.8 without the extender and compare those results from your previous calibration. If those are the same, then you will know that the extender is the culprit. Good luck!

 

[eos650]

Good idea, I'll give that a shot.

Thanks!

FYI: I did just calibrate the 1DX with the 400mm and 1.4X and it did move in the same direction, but only by a small amount. It went from +8 to +5, so only a 3 point swing.

 

[eos650]

I just AFMA'ed the 5D III with the EF 400mm f2.8 and it actually went the other way. It went from +3 to +6. It sounds like I may need to send my 1.4x back to Canon to be checked and calibrated.

Thanks!

 

[Mt Spokane Photography]

This is a pretty common finding, its difficult to get a accurate AFMA setting, and a lot of factors affect autofocus.

I've found that Focal does a much better and more reliable job than some of the other methods.

In the end, it can also be a lens issue, even if you did not do anything to the lens recently, there could have been a pre-existing issue.

Focal has a focus consistency test that can highlight focus issues with a lens, it does a lot more than just AFMA.

 

[Random Orbits]

Yes, TCs can affect AFMA quite a bit. If you use all Canon gear, at least the camera allows you to have different AFMA settings for each combination. I don't know how that works once 3rd party gear is introduced...

I had a similar issue when I first got the 2x III. I had a AFMA value for my 70-200, but when the 2x was mounted, it was a separate combination so everything was set to 0. Once I realized it and did AFMA with the combo, the images became much sharper. Took me a while to figure that out -- thought that the 2x was defective for a while.

 

[Don Haines]

A lens with the TC and the lens without are like two completely different lenses... you need to AFMA the bare lens and you need to AFMA the combo...

 

[Maximilian]

A lens with the TC and the lens without are like two completely different lenses... you need to AFMA the bare lens and you need to AFMA the combo...

+1

If you did compare AFMA results bare lens+Body to Lens+TC+body the difference wouldn't surpise me.
I suppose, you could go one aferter AFMA of Lens+TC+body without sending the TC to support.

 

[pwp]

Yikes! Where does this leave the EF 200-400mm f/4L IS USM Lens with Internal 1.4x Extender from a AFMA viewpoint?

-pw

 

[Maximilian]

Yikes! Where does this leave the EF 200-400mm f/4L IS USM Lens with Internal 1.4x Extender from a AFMA viewpoint?

I didn't have the time to get my yet to be bought 200-400 with my yet to be saved up money AFMAed
But I think I can recall that the lens reports to the body if the internal TC is turned in or not.
So different AFMA settings should be possible.

But: Good question. Maybe someone else knows better.

 

[Hispany]

Yikes! Where does this leave the EF 200-400mm f/4L IS USM Lens with Internal 1.4x Extender from a AFMA viewpoint?

I didn't have the time to get my yet to be bought 200-400 with my yet to be saved up money AFMAed
But I think I can recall that the lens reports to the body if the internal TC is turned in or not.
So different AFMA settings should be possible.

But: Good question. Maybe someone else knows better.

Thats correct Maximilian. The 200-400 reports when extender is used, so it can be AFMAed (is that even a word?) in all 4 scenarios (wide, tele, wide+ext, tele+ext).

 

[mackguyver]

I've had some changes, but usually in the 3-5 range, and that's after several months or more. Some things that could affect the settings are shooting distance, which focus points are used, and if extreme, temperature. I don't imagine these played any role, but maybe you bumped the camera or it was bumped/vibrated a lot in the vehicle?