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09/24/2007 03:48:28 PM · #1 |
[thumb]591136[/thumb]
What's up with the blue fringe?
Is it from back lighting?
Is there a place in RAW or CS3 to deal with it, or do I get to try to pick it out.
Not worth it on this zoomed in image but it will come up again. |
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09/24/2007 03:53:55 PM · #2 |
CA or chromatic aberation (spelling is probably off).
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09/24/2007 03:53:55 PM · #3 |
| could be when you sat the colors......I think |
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09/24/2007 03:55:48 PM · #4 |
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09/24/2007 04:03:56 PM · #5 |
Chromatic aberration. Each frequency of light is bent slightly differently by a lens, so the focus will be slightly different.
CA is generally much worse at the edges of a lens; this looks like it's a tight crop from either the top of the bottom of an image?
It's directional (tends to be radial to the primary lens axis. Can be corrected to some degree in PS (so I hear - I don't use it) though I expect this goes beyond what can be saved. Expensive lenses will minimize, though not eliminate, CA.
To some degree the charges on a CCD can bleed to adjacent pixels when one pixel is saturated, as well - this is called "blooming" and is what bvlindalou is referring to. This may or may not be at play in this image.
//www.dpreview.com/learn/?/key=chromatic+aberration
//www.dpreview.com/learn/?/key=blooming
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09/24/2007 04:22:52 PM · #6 |
Unless this is a 100% crop ... I wouldn't expect CA to be so large. Is this the original or have you edited it? If you've edited it, do you have the original that we can look at?
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09/24/2007 04:40:37 PM · #7 |
Thanks for all the replies.
Here is a full crop
[thumb]591149[/thumb] |
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09/24/2007 04:42:03 PM · #8 |
Wiki is your friend...chromatic aberration. :-)
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09/24/2007 04:53:53 PM · #9 |
Nobody has really been able to make a good 70-300 range lens yet. It's the price you pay for the versatility.
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09/24/2007 05:03:50 PM · #10 |
Originally posted by DrAchoo:
Nobody has really been able to make a good 70-300 range lens yet. It's the price you pay for the versatility. |
LOL
When I went DSLR I promised I wouldn't clutter up my bag with a lot of budget lenses, but I'm too impatient. I just try to keep the focal length under 200mm.
Since this IS chromatic aberration should I be able to fix it in Adobe Raw under "Lens Correction"? It doesn't seem to help.
Fix Red/Cyan and Fix Blue/Yellow
What are these 2 sliders are for if not this?
Is this just too much?
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09/24/2007 05:09:01 PM · #11 |
| This one's an interesting one. Not what I'm used to seeing with typical CA. Open the shot in PS, and click on the Channels Tab in the Layers Palette. Now click on each of the R, G and B channels in sequence. See what the Blue channel looks like? It's not shifted with respect to the Red and Green. but has a strong "halo." This is not CA but looks more like blooming on the Blue channel. It could be lens-related (scattered blue light) or it could be the sensor blooming. The fact that it only appears on the bright white area makes me think it's sensor related. I could very well be wrong, though. |
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09/24/2007 05:09:57 PM · #12 |
Originally posted by BlueZamia:
Originally posted by DrAchoo:
Nobody has really been able to make a good 70-300 range lens yet. It's the price you pay for the versatility. |
LOL
When I went DSLR I promised I wouldn't clutter up my bag with a lot of budget lenses, but I'm too impatient. I just try to keep the focal length under 200mm.
Since this IS chromatic aberration should I be able to fix it in Adobe Raw under "Lens Correction"? It doesn't seem to help.
Fix Red/Cyan and Fix Blue/Yellow
What are these 2 sliders are for if not this?
Is this just too much? |
I've never used that tool but that's what it's for. Just duplicate the layer and blur the heck out of it, then change the blending mode to color and you should see a marked improvement. You may need to tweak it a little afterwards if you have some color bleeding elsewhere but it shouldn't be too bad.
Message edited by author 2007-09-24 17:29:02.
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09/24/2007 05:30:16 PM · #13 |
I'm curious what we would see if you were to shoot a black and white checkerboard pattern (fill the frame from edge to edge). Try it with the same lens you used here. And try it again with a different lens.
That should tell us if it is sensor related or lens related. And if lens related, whether it goes all the way out to the edges or not.
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09/24/2007 05:42:16 PM · #14 |
You asked if there was a way to take care of this in CS2(3). Yes. There is a lens adjustment tab (in Camera Raw) and you can fix the chromatic abberation there. Alternatively, you can go into the Filter > Distort > Lens correction option and fix it there.
When you do, be sure to hold the alt (option) button down (in Camera Raw). This will hide the channels so you can see exactly what you are doing. Also, remove any sharpening from Camera Raw when you do this. Finally, you should be at at least 100 % zoom.
I'd also get that lens checked out. Tamron is a good lens manufacturer. I have a Quantaray 70-300, cheap because I only use it once or twice a year, and I don't get nearly the CA that you get with that.
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09/24/2007 06:00:33 PM · #15 |
Originally posted by yanko:
Originally posted by BlueZamia:
Originally posted by DrAchoo:
Nobody has really been able to make a good 70-300 range lens yet. It's the price you pay for the versatility. |
LOL
When I went DSLR I promised I wouldn't clutter up my bag with a lot of budget lenses, but I'm too impatient. I just try to keep the focal length under 200mm.
Since this IS chromatic aberration should I be able to fix it in Adobe Raw under "Lens Correction"? It doesn't seem to help.
Fix Red/Cyan and Fix Blue/Yellow
What are these 2 sliders are for if not this?
Is this just too much? |
I've never used that tool but that's what it's for. Just duplicate the layer and blur the heck out of it, then change the blending mode to color and you should see a marked improvement. You may need to tweak it a little afterwards if you have some color bleeding elsewhere but it shouldn't be too bad. |
Your method may work but isn't legal in basic. Does it have any negative effects on the image to do it this way? |
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09/24/2007 06:10:48 PM · #16 |
Originally posted by mad_brewer:
Originally posted by yanko:
Originally posted by BlueZamia:
Originally posted by DrAchoo:
Nobody has really been able to make a good 70-300 range lens yet. It's the price you pay for the versatility. |
LOL
When I went DSLR I promised I wouldn't clutter up my bag with a lot of budget lenses, but I'm too impatient. I just try to keep the focal length under 200mm.
Since this IS chromatic aberration should I be able to fix it in Adobe Raw under "Lens Correction"? It doesn't seem to help.
Fix Red/Cyan and Fix Blue/Yellow
What are these 2 sliders are for if not this?
Is this just too much? |
I've never used that tool but that's what it's for. Just duplicate the layer and blur the heck out of it, then change the blending mode to color and you should see a marked improvement. You may need to tweak it a little afterwards if you have some color bleeding elsewhere but it shouldn't be too bad. |
Your method may work but isn't legal in basic. Does it have any negative effects on the image to do it this way? |
It can produce color bleeding that you don't want. If applied to the photo in this thread it probably would dull the color in the bird's beak as the surrounding color would easily bleed into it and passed it if you use a strong blur. However, this photo is an extreme case of CA (or whatever it is) so normally this technique wouldn't cause much problems but even if it does you can always use a rough mask to protect the areas you don't want effected which would be skinny things where the color would easily bleed over such as the bird's beak, the legs, etc. I don't have much issues with CA so I don't do this very often but when I have it's worked great.
ETA: And yes definitely not legal in basic.
Message edited by author 2007-09-24 18:12:34.
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