Lens problem orTC or 1D MKIII lens calibration

[Wally Nussbaumer]

I was out taking images of mountain bluebirds yesterday...a bright sunny day, no cloud. Most times the bird would be sitting on an old rusty barbed wire fence. When I looked at the images I had taken I noticed that the barbed wire fence looked normal at viewing size, but when I started to look at it blown up by about 4-500% I noticed sort of a blue and green halo around the wire. First I thought it seemed to appear only in the shade, not full sun, or at least not that visible. But after quickly checking all the images it was just more noticable in the sharp focus area under the bird and diminished as it got further OOF. Anyone got an idea what may be causing this. First I thought it was my lens, then I thought it was the 1.4 TC, I am leaning toward the TC.
I have never noticed this with my 20D with that combination, just my new 1D MKIII:confused:

[Roger Clark]

Wally,
What lens and what 1.4x TC? A good lens out of focus could do this, but consumer grade lenses can do it in focus too.
Roger

[Wally Nussbaumer]

Canon EF 400mm USM L series f/5.6, I am leaning towards Canons 1.4 TC II, but what puzzles me is that I never noticed it when I used the combination on my 20D

[Robert O'Toole]

Its the 1.4X.
This is lateral color and it mostly shows up with strong lighting especially with a Extender wide open. If you want to repeat the problem shoot something strongly backlit like a tree branch or fence. You should see blue and purple fringing. Stopping down some helps minimize it.

Robert

[Wally Nussbaumer]

Thanks, I'll give it a test. Odd that I never noticed it with the 20D though.

[Axel Hildebrandt]

I agree with Robert, stopping down a bit helps and you can remove the rest in your RAW converter. The new version of ACR for example has a well-working lens correction tool.

[Robert Amoruso]

Some good explanations here:

http://www.vanwalree.com/optics/chromatic.html