fringing with dark against high contrast-help

[Carl911]

I recently took some pictures of trees in a wood.
Between the trees there was a bright white background which caused a considerable amount of colour fringinging, in particular, magenta & blue.
i was able to remove most of this in photoshop but I was a little surprised to see such a bad case of this from my 40D and 17-85mm lense.
Is there something I can do to avoid this happening again or is it just a case of not taking pictures of dark objects against bright backgrounds.
Any tips on this appreciated.
Is it the lense itself that may be parlty to blame?

Cheers Carl

[zona5101]

Could you post the image you are refering to???

[Carl911]

Originally Posted by zona5101

Could you post the image you are refering to???

This is the picture. I have actually posted it as a view my image but I have photoshopped this to remove as best I can the fringing that was very bad up the vertical edges of the trees. Some is still evident in the branches etc.
Even though I have removed the colour you can still make out some ghosting where it was.

[zona5101]

my eyes must be tired as i don't see what you're describing...i looked at the larger size on your flickr and didn't notice the problem...i am not on the best monitor or in the best room light now either. Perhaps someone else will be able to help...

[candleman]

i can see it..

i believe its "Chromatic abberation" and its Cyan and Magenta.. not blue

anyway, generally its caused by poor quality glass, and in contrasting situations like this.
Wikipedia it for an explaination..

i'm surprised its that bad tho'... so i'm semi-stumped

[kencaleno]

lateral chromatic aberration (fringing) can be green;yellow;blue;cyan;magenta, etc.,and is due to red green and blue light waves unable to focus on a common focal point on your sensor,better lenses do help, but to really control fringing you have to lay out big money for apochromatic lenses,which employ special doublet elements,to bring all three light wave to a common point. Best way for now to reduce this, is to not use extreme ends of your zoom lenses,and you will see a difference. The biggest offenders of this phenomenon, are the superzoom cameras,often erroniously referred to as "Bridge Cameras". Post process methods include:

- Lateral chromatic aberration (fringing) Removal

Ctrl+J select brush tool and click on the quick mask tool.
Choose a brush size to match the width of the fringe.
Draw all the areas that have fringing. When done, click icon next to quick mask
Select> Inverse.
Image> Adjustments> Hue/Saturation and pick the color closest to your fringe color Click eyedropper on the fringe color on your image.
drag Saturation slider to the left until the fringing goes.
Select> deselect
Save

Quick method for fringe elimination

Using lasso tool select area with fringing
Image> adjustments> Hue/Saturation
De saturate fringe color
Select> Deselect
save

- Transverse chromatic aberration (Moire banding) Elimination

- Filters/blur/Gaussian Blur at 1.5 pixels radius

regards, Ken

[Carl911]

Thanks for the replies.
I was using my 17-85 lense at 17mm. Maybe next time I should try 20-25mm.
Thanks for the tips on removal ken, Ill make a note of that for next time.
As I say, this is the first time I have ever noticed it on my new camera.
Im saving up for a 17-40mm lense which will hopefully be an improvement on my 17-85.
I would like the 16-35 but thats a bit expensive for my budget.

Carl