What caused this halo?

[Stagecoach]

I noticed this halo on one of my wasp shots of today that has not been caused by any processing.

Lighting was the two SB200s (at equal power) on the front of the lens roughly opposed.

The image is from the raw, opened in ACR, default sharpening zeroed, nothing done but opened in PS, cropped and downsized.

Any ideas? I know it's easy to sort but just interested because I have not come across anything similar in the zillions of other similar shots I have taken.



Grahame

[DanK]

It's also on the top edge of the leg above the higher of the two white lines you drew. I think there may be some on the back of the thorax as well.

Could it be chromatic aberration? Is this one that you shot with a telextender? I use Canon equipment, but I sometimes notice degradation when I couple my 1.4x telextender (model II) with my 70-200.

[Stagecoach]

Could it be chromatic aberration?

I opened it in ACR Dan and adjusted CA/Defringe through the range, no difference at all.

Is this one that you shot with a telextender? I use Canon equipment, but I sometimes notice degradation when I couple my 1.4x telextender (model II) with my 70-200.

Yes, this is one of many with the 1.4TX but I can find nothing similar on any other shot.

I'm starting to wonder about 'light reflection' and is it something caused by the specific position of the lights in this shot, I was regularly moving the flashes around.

[odds]

I opened it in ACR Dan and adjusted CA/Defringe through the range, no difference at all.

It looks like halos appear just beyond the far DOF-plane, which makes me wonder if it is a "bokeh feature" of the optics, including the TC.

You may try to rig a test-series with a static and less hostile subject and shoot with varying apertures, optics and lighting to see if you can reproduce halos (preferably make them appear worse than in your wasp image) and then try to fine tune parameters to study effects on edges near the far DOF-plane.

If you haven't done so already, try reprocessing the raw file with a linear profile and no automatic software "enhancements". Manually adjust that dark dull image in small steps towards the final result while you inspect the halo areas. If software cleverness plays a role here, you may be able to work around it.

--
Odd S.