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-   -   clean white (https://forums.steves-digicams.com/tips-tricks-71/clean-white-197305/)

stilllearning66 Mar 21, 2012 10:04 AM

clean white
 
I was taking photos of these white herons against a dark green background ( the leaves :) and when I looked at them on a big screen when I got home, all the white bits were sort of lined with pink/ purple. Why was this ? Is there a way to avoid it?

Thanks for your help:) And sorry if this question has already been answered somewhere

TCav Mar 21, 2012 10:29 AM

It could be from a number of different sources. Can you post a 100% crop of what you're talking about?

VTphotog Mar 21, 2012 6:51 PM

This is fairly common where white is overexposed - the edges of the overexposed areas show this kind of color fringing. The overexposure is probably due to the camera averaging in the darker background.

brian

stilllearning66 Mar 22, 2012 11:50 AM

So would it go away if I lowered the exposure?
Thanks

VTphotog Mar 22, 2012 12:16 PM

Probably. Another way, if your camera allows, is to spot meter. Also, if your camera has a histogram available, use it to see if there is a peak on the right hand side. This would indicate blown out highlights. I like to do a quick view, with histogram when I am in doubt. How you deal with tricky exposures can depend a lot on your camera's features.

brian

stilllearning66 Mar 22, 2012 12:55 PM

spot meter?
Sorry I'm not very good with all things photography...

TCav Mar 22, 2012 1:05 PM

Your problem may also be chromatic aberration. That's why I'd like to see exactly what you're seeing.

stilllearning66 Mar 23, 2012 11:51 AM

Sorry TCav, my parents are very protective and were already reluctant to let me join this site i the first place so they won't let me post any photos :(
I'm sorry. Looking back at the photos though, I have noticed that the problem occurs mostly (and more strongly) on the photos where the white birds are in flight, when they are moving.

chromatic aberration??
thanks

VTphotog Mar 23, 2012 5:00 PM

Can you tell us a bit about your camera model and what features it has? This may give us some clues as to what is happening, and ways to fix it.

brian

TCav Mar 23, 2012 5:32 PM

There are two types of Chromatic Aberration:
  • Axial (or longitudinal) presents consistant color fringes across the entire image in high contrast borders (i.e.: bright or white areas surrounded by black or dark areas.) The fringes would be, for instance, red on the left side of the bright areas, and blue on the right side. Axial Chromatic Aberration can be reduced by using a smaller aperture.
  • Transverse (or lateral) presents almost no color fringes in the center of the image, and the fringes would be more pronounced as they appear farther from the center. In addition, the same color fringe will appear on the outside of the border areas, and the opposite color fringe will appear toward the center of the frame.
You may also be seeing somethinn called Blooming, which is when the photoreceptors are overloaded with light. It's a blown highlight. That is, one or more small portions of the image are severely overexposed, even though the entire image is properly exposed.


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