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06-25-2008, 04:55 PM   #1
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Strange Haloing... Help me solve.

I'm somewhat new to photography, but have found that in a few cases with my K10D that there's haloing around high-contrast edges.

What I'd like to know is:

How do I avoid this when I shoot the original photo? (or minimize it)

Are there any commonly used techniques to correct this in post?

Note attached image is slightly color corrected, and rotated to increase size. This is a 1:1 snapshot of a photo.

I've also shown two of the channels where it occurs the worst. Notice in both the Red and Blue channel there is a bright halo that extends from the outer edges of the ring inward. The Blue channel also has a very hard edge, which I thought was strange.

It's also slightly green on the bottom, and slightly red on the top. (remember the attachment is rotated). It even occurs in relatively lower contrast areas, which you can see in the edge of the far right ring.

Any advice would be greatly appreciated!

Thanks,

.:: Epoch

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06-25-2008, 05:05 PM   #2
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Turn down your sharpening!!!!
It looks like you might have a little bit of chromatic abberation going on as well, but sometimes oversharpenning will give weird artifacts.
06-25-2008, 05:19 PM   #3
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No sharpening was on in the camera.

That's one of the first things I turned off when I got the K10. It was also shot in RAW (DNG) and no color correction routines applied. Basically every setting that assures what gets stuffed onto the SD Card is unaltered. (I prefer to leave it to Photoshop than the camera)

I just double checked, and ACR had sharpening "To all photos" on, which made a very slight difference in the hard edge on the Blue channel. Glad that's caught and out of the way now.
06-25-2008, 05:28 PM   #4
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What lens were you using with these photos? That could have something to do with it too.

06-25-2008, 05:35 PM   #5
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The kit lens. I'm not sure what version, but I bought it new last summer.
06-25-2008, 07:03 PM   #6
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QuoteOriginally posted by Epoch of Entropy Quote
The kit lens. I'm not sure what version, but I bought it new last summer.
I've never seen that with my K10D. It looks like a CRT that has the electron gun out of adjustment.

You have a cheap UV filter on it or something? Does it occur with other lenses?
06-25-2008, 08:31 PM   #7
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QuoteOriginally posted by Epoch of Entropy Quote
No sharpening was on in the camera.

That's one of the first things I turned off when I got the K10. It was also shot in RAW (DNG) and no color correction routines applied. Basically every setting that assures what gets stuffed onto the SD Card is unaltered. (I prefer to leave it to Photoshop than the camera)

I just double checked, and ACR had sharpening "To all photos" on, which made a very slight difference in the hard edge on the Blue channel. Glad that's caught and out of the way now.
My next bet would be that you've managed to induce some aliasing.
06-26-2008, 12:20 AM   #8
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QuoteOriginally posted by Epoch of Entropy Quote
The kit lens. I'm not sure what version, but I bought it new last summer.
that's the first version, the II didn't come out until this year I believe...

06-26-2008, 01:51 AM   #9
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Do you have a different lens to try the same ?

Some lens do exhibit halo'ing around high contrast areas although have never heard of kit lens doing it. I recommend you try out a similar lens for the same shot or a different lens to rule out the body.

Cheers
Nish
06-27-2008, 09:17 AM   #10
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QuoteOriginally posted by konraDarnok Quote
You have a cheap UV filter on it or something? Does it occur with other lenses?
I've got a Heliopan UV filter that I keep attached to the kit lens at all time. I was assured that this is some of the best glass filters you can get.

QuoteOriginally posted by bnishanth Quote
Do you have a different lens to try the same ?

Some lens do exhibit halo'ing around high contrast areas although have never heard of kit lens doing it. I recommend you try out a similar lens for the same shot or a different lens to rule out the body.
I want to setup a high-contrast test with the kit lens and my tamron 70-200, to see if it's the lenses. With the suggestion above, I will also test the kit lens with and without the filter.
06-27-2008, 09:54 AM   #11
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What ever the cause, it removes quite easily with the chromatic abboration tool in PSP X2
06-30-2008, 03:42 PM   #12
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A quick follow up:

I did some tests with the kit lens and high contrast subjects. At home I made some longish exposures of a dark item on a bright white table with incandescent lighting. I set up the camera on a tripod, set the exposure timer to 10secs (to eliminate wobble as the cause) I focused right on the edge of the subjects.

What I found was that at higher apertures, there was distinct haloing.

This was resolved at around F5.6 where it was barely perceptible. Using any smaller aperture and it disappeared almost completely.

I will attach 100% zooms of screens if anyone wants.
06-30-2008, 04:31 PM   #13
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Epoch,

I am the first to admit that my technical knowledge is not the best, nor my eye for technical details -- but to me, it looks like CA/PF (chromatic aberration/purple fringing) caused by your lens. Some lenses -- particularly less expensive ones or superzooms -- exhibit this to a greater degree than high-quality glass. Even different copies of the same lens can have varying degrees of the problem, caused by misaligned internal components.

At any rate, my opinion is that it's a function of your kit lens. Have you seen the same problems with your 70-300?
06-30-2008, 04:54 PM   #14
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I haven't tried with the Tamron yet, but I will soon.

I also didn't take the UV filter off the kit lens, which may be affecting things at larger apertures.

Any useful info and I will report back.

This is making me think that buying lenses from the local shop is good. Trying them out there and finding one that has the best performance. I'm sure these guys have stringent manufacturing tolerances though, so it might be a waste of time.
06-30-2008, 07:45 PM   #15
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The kit lens is pretty good at controlling CA/PF, but it does creep in from time to time. However, it's usually pretty subtle. I tend to see it show mostly as green, sometimes as blue, and rarely as purple on this lens. While using a filter isn't certain to cause it, using one will never be better than not using one.
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