In a discussion with Vonkara in another thread, he posted some tables comparing the CA of a prime 50mm and a 18-125 Sigma Zoom, gold band. The worst number was around 0.8 px there. I'm using the latter zoom lens on a D200 as an allround lens but some wide angle landscape shots in the tropics show fringe that is much higher.

I'm posting some shots here for advice. Is this normal? The CA seems well above 0.8 px. Am I doing something wrong?
Note: same lens, no CA visible in studio.

1. Overview.



Location: 8 degrees N of equator, april, sun exactly in azimuth at 11.30am; time of shot 9am, sun around 35 degrees from the left, very hard, clear morning.

Nikon D200 - raw with no adjustements except exposure from 1 to 1.15;
Sigma 18-125 DC 1:3.5-1:5.6
ISO 100, 1/160s, F10, 18mm, all raw settings "normal"

2. Clip 1: shadows on pavement right-center-bottom


Top: 1:1. Bottom: 700%. Seems to exceed 0.8 pix, right?

3. Clip 2: trees left-center-top


300% and 1:1

4. Clip 3: tree stem left-center-top


Only 500%

5. Clips 4: uploaded version




Since the shot was borderline focused, I uploaded it reduced from 10 to 4MP, with lightness channel sharpening of 0.9px, 22% and removed the fringe. The process took 20mins which is not really productive. The clips are 1:1.

Thanks for any thoughts.

Yes I recently discovered that Lightroom trick too.  Works great!  You can "shift" the fringe a bit to the left/right and make it disappear, and also change its color.  That's 2 minutes instead of 20.  Well worth a try!

Call me a cowboy.... but I bit running a de-saturation tool over the fringed pavement area would probably clear that up for you! ;-)

That's what I do to, a 50% soft brush at the side where there is the least harm: the tree stems and not the foliage.

Thanks to LisaFX and Anyka for having a look. It's all a matter of workflow and time involved. Lightroom might be an option apparently, but to invest time and money in Lightroom just for that is perhaps counterproductive. On the Ken Rockwell site I read that the D90 does it in cam, like the D300, but I'm not sure about the reliability of Rockwell.

Can't you use Adobe Camera raw?
It has CA removal tools.
Works quite well and it only takes a few seconds.
You have to shoot raw, though.

Yes I'm always doing raw. I'll check. I reverted to my old CS2 and the raw developer is quite rudimentary.

Quote from: e-person on March 01, 2009, 13:02

Can't you use Adobe Camera raw?
It has CA removal tools.
Works quite well and it only takes a few seconds.
You have to shoot raw, though.

Yes I'm always doing raw. I'll check. I reverted to my old CS2 and the raw developer is quite rudimentary.

Unfortunately, CS2 does have a worse version of ACR. You need at least CS3 to see the improvements ACR 4.4 brought. I use ACR 4.6.