Hey guys! A friend of mine got her first DSLR (Canon Rebel T3 with kit lenses), and is still learning how to use it with the non-manual settings.... she took it with her to Sanibel Island on vacation, and got some great shots of the wildlife there. But on a few of her shots of white birds, she notices a purple-hazy line on the edge of over-exposed white areas of film... this is an example.... so in your opinion, is this purple haze a product of user error / over exposure of the white areas, or a bad lens? Thanks in advance!
Purple fringing can be lens related or sensor related. Even if it is lens related, this does not necessarily indicate the lens is "bad." Kit lenses tend to be on the less expensive end of the range, therefore will generally not have as many corrective measures built in. Buying a lens designed to counter such will reduce this, but not eliminate it. Software can clean this up as well. Purple fringing, longer explanation.
Agree with @jenp . Kit lenses are plastic. If this is the way it looks before posting to the web, that's one thing. If it only looks like that after posting on the web, then maybe she should "save for web" or do a slight unsharp mask, it that would help (not sure)
I've read that there's a difference between purple fringing and chromatic abberation. I've even read why they are different, but the technical explanations are all over my head. From a practical point of view, some lenses have more of it than others. It's worse with some apertures than others. If it's purple fringing you will see it mostly at high contrast edges (like here), while CA can be found at other edges. Older lenses made for film cameras tend to be more prone to both (especially purple fringing) on a digital camera than lenses designed for digital sensors - digital sensors are more sensitive to such things. Some lenses have better coatings to combat these things than others. Solutions include avoiding high contrast situations (yeah, right - not very practical as far as I'm concerned), trying to avoid shooting a lens wide open (some lenses have a lot less CA when stopped down a bit), and correcting with software (which is how I deal with it - LR4 has nice, simple tools for both fringing and CA). For white birds, since so often they become white, featureless blobs (can't tell you how many shots I have like that!), try dialing in a -Ev to underexpose the shot. They won't be so blown out and you won't get so much fringing.
@mikew ... why the spam alert? I am not a professional, have never taken any classes, started with a kit lens myself and never ran into this problem. So when Karen asked, I figured is come ask those who would know!
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Purple fringing, longer explanation.