18-200 VR giving me purple/blue outlines -- Chromatic Aberration

[kithg]

Hello, I have an 18-200 VR lens that I use on my D50. I've had the lens since

February, but the longer I shoot, the more educated my eye is becoming, and

I'm seeing things I didn't used to notice. Every so often, I will find a one

or two pixel outline of some subject in blue or bluish purple. It's likliest

to happen if the background is light, but not necessarily. I've had a bright

blue outline around a purple iris against a green background. Or purple

outlines of tree branches against our classic Philadelphia "white sky of

summer." My question is this: Is this outlining (I'm not sure what to call

it.) a fault I can send this lens back to Nikon to fix? Or is it one of the

compromises one needs to accept in a very long zoom like the 18-200? Thanks

for your experience!

[tom_jenner1]

Hey Kit,

 

You need to live with it. What you have is a type of "chromatic abberration" called "purple fringing". There may some other types of chromatic aberations going on. It tends to happen where there is a high contrast in the scene. One or two pixels is fairly typical for a hyperzoom lens like yours. A good, cheap prime lens like the 50mm f1.8 will have much less purple fringing and chromatic aberations.

 

Check out http://en.wikipedia.org/wiki/Purple_fringing for a little more info.

 

Hope this helps!

 

-Tom

[robert_martin5]

A lens with a wide zoom range will have a problem like this. I have the 18-200 VR lens for my D200 and see the same thing. The amount of fringing is a function of the focal length you are using. At some focal lengths you will not have any fringing. You can correct this for each image with Photoshop CS2. If you are using RAW, this correction is under the lens tab of the Adobe RAW converter. If JPG, TIF, others use the Filter > Distort > lens correction. Zoom in at a high magnification along the edge of the image to make the adjustments.

[juan_parm_nides]

Hello Kit, I have the same lens and the same issue. Not noticeable if you print Din A3 (aprox 15 x 20 inches). And as Robert says, easy solution with CS2. Cheers.

[j_c38]

Even the top end glass will have this from time to time. I have a 17-55 and have gotten before. Only once or twice in a very high contrast scene. Only in a small portion of the image.

[kithg]

Thanks very much for all of your answers. I appreciate your clarity and promptness very much.

[elliot1]

there are numerous software programs that automatically correct purple fringing automatically.

[kithg]

Thanks Eliot and Peter. This is not a problem bad enough for me to villify the lens and immediately offer it for sale on e-bat. It's just something I've noticed on a few of my pictures under very specific circumstances. I consider it part of my eye-training that I'm now seeing things I used to miss. Peter, your three step process makes a lot of sense. Thanks.

[see_r]

"You can correct this for each image with Photoshop CS2."

 

Well...there is a feature do do this...but it does not work at all. Not one bit...perfectly useless.

[lex_jenkins]

Corel's Paint Shop Pro X has a couple of utilities for correcting CA and purple fringing, both of which are simple and effective.