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View Full Version : chromatic abberation?



Kawarthabob
05-06-2010, 06:16 PM
I mainly use my 75-300mm lens to shoot wildlife. It seems that taking shots of the local bird population is hit and miss and while i seem to get off a good shot once in a while there is a bit of chromatic abberation in the pic. How do i solve this?

kat
05-06-2010, 06:53 PM
I just started some searches and really didn't come up with much in the way of help. I don't have the greatest knowledge on ca and purple fringing. I do know I get it as well and it's a pain.
I'm sure someone here will soon assist you further!

Some sights I've come across..although not sure how well they are. I hate the web for that..

Digital Photography World: CORRECTING CHROMATIC ABBERATIONS (http://www.paintedstork.com/digiblog/2005/07/correcting-chromatic-abberations.html)

http://www.brighthub.com/multimedia/photography/articles/33825.aspx

Mad Aussie
05-06-2010, 08:18 PM
CA occurs when a very bright section of pixels meets a very dark section of pixels. Some lenses are more sensitive to this than others. Trying to avoid it is the first thing but often it can't be avoided of course.

Lightroom has a good tool for removing CA at both the cyan and the purple end of the spectrum.
If you don't have LR, or it doesn't completely remove the CA then a program like photoshop is the next step for me.

Sometimes using the lasso tool to isolate the area in question and then using the replace colour tool words well.

Also, if needed I will duplicate the layer and then desaturate the lower layer and then use a layer mask to blend the now desaturated CA though to the top layer. A bit of contrast on the lower layer after that often helps as well.

Grant
05-06-2010, 08:53 PM
I guess the best way to avoid the purples is not to shoot against heavily back light but that is not often the real life.

First, an ultra violet filter may help.


But

The easiest way of eliminating them, in post process, is to create a Hugh/Saturation adjustment layer. Don't use the MASTER control in Edit. In your first image I selected the Edit: > Blue then used the eye dropper to identify the blue around the grackle and I dropped the Saturation to -50 and the Lightness to -28 and the fringe was gone. Also there is a slight green fringe at the bottom of some of the tree branches so I then switched to Edit: Green, selected the offensive colour with the eye dropper and dropped the Saturation to -75, no fine tuning was needed with the Lightness. The numbers are not constant as each image seems to be different but the good news is that the change is obvious so you will have not trouble seen the changes.

While it sounds complicated once you have done it you will see it is a very easy process,