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Old December 2nd, 2007, 07:24 PM   #1
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Tips for Limiting Chromatic abberration

There's a lot of talk of CA, but there isn't a resource that spells out guidelines for preventing CA. Here are some instances that have caused CA for me.

For starters,

1) Avoid shooting through the long end of the lens

2) Avoid shooting with lens wide open

3) Avoid Bright/contrasty backgrounds.

What are some others?
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Old December 2nd, 2007, 09:07 PM   #2
 
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there's a few plugins that will remove CA. The one I use works with VirtualDub...not perfect, but, better than no correction.
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Old December 3rd, 2007, 01:45 AM   #3
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Quote:
Originally Posted by Bill Ravens View Post
there's a few plugins that will remove CA. The one I use works with VirtualDub...not perfect, but, better than no correction.
Thanks by I was thinking more along the lines of camera/lens settings. IE avoiding it in the first place.
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Old December 3rd, 2007, 03:04 AM   #4
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It sounds to me Bruce as if the fear of CA could be limiting your shooting options somewhat. Shooting wedding guests at the long end of the zoom and at maximum aperture sure does raise the CA levels, but at the same time the flattering perspective, the differential focus and the lack of intimidation gives me the portraits I want.

You might say that you shouldn't shoot at full wide because of the barrel distortion so prevalent in camcorders, but most clients want the perspective shots and won't be looking at the vignetting way up there in the corners.

tom.
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Old December 3rd, 2007, 08:23 AM   #5
 
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Brian...

There's not much you can do to reduce CA other than the items you listed. It's a weakness of the lens design. The most effective option, of course, is to change your lens. You may want to consider more fill light to reduce contrast, but, the wedding party might object as it's rather intrusive.
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Old December 3rd, 2007, 09:25 AM   #6
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can someone post a ca Sample? a Photo or something

what is that anyway?
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Old December 3rd, 2007, 09:35 AM   #7
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Chromatic abberation? When not all colours are brought to the same focus point. Jeff explains it well here:

http://www.dvinfo.net/articles/optics/lensdefects.php
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Old December 3rd, 2007, 09:38 AM   #8
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What's the "long end of the lens"? Is it zoom?

What's "wide open"? Is it the iris setting? ???
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Old December 3rd, 2007, 09:42 AM   #9
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The long end is the longer focal lengths. Wide open refers to the iris, yes.
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Old December 3rd, 2007, 12:23 PM   #10
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I've also heard of shooters getting CA at the wide end of the lens, anyone experience this?
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Old December 3rd, 2007, 01:10 PM   #11
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Thanks Tom
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Old December 3rd, 2007, 05:58 PM   #12
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Depending on how you shoot

whether tripod or shoulder, I find if I'm on a tripod I shoot using the flip out LCD, and I use the hoodman on it to reduce glare and solarization. I've found that I've learnt to look out for it, and as such I will pull back the zoom slightly to either get rid of the CA or diminish it.
The EVF you can probably do the same, but either it doesn't resolve enough to see it, or I just haven't observed it yet, as it was only on my last shoot I bothered to pay attention to it.
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