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Author Topic: Banding in photo  (Read 3319 times)

Craig Murphy

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Banding in photo
« on: February 23, 2008, 10:59:02 am »

Can anyone tell me what is causing the circular bands you see in this image?  It was created by filling a new file with green, then on a new layer with a darker green, then punching a hole for the center spotlight look.   I have seen this happen with other images when attempting vignettes.  I am on a NEC 2690.
« Last Edit: February 23, 2008, 11:02:30 am by Craig Murphy »
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Ken Bennett

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Banding in photo
« Reply #1 on: February 23, 2008, 11:30:01 am »

Are you working in 8-bit or 16-bit? Gradients without banding are one of the reasons to work in 16-bit mode. It doesn't always fix the problem, but it helps.
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Anthony R

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Banding in photo
« Reply #2 on: February 23, 2008, 12:30:09 pm »

Please google what banding is and why it happens. It's not simply an 8 bit vs 16 bit deal, far from it.
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Craig Murphy

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Banding in photo
« Reply #3 on: February 23, 2008, 02:38:42 pm »

8 Bit, 16 Bit.  No real difference.  Is this a monitor issue or a file issue?
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John Sheehy

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Banding in photo
« Reply #4 on: February 23, 2008, 06:28:56 pm »

Quote
Can anyone tell me what is causing the circular bands you see in this image?  It was created by filling a new file with green, then on a new layer with a darker green, then punching a hole for the center spotlight look.   I have seen this happen with other images when attempting vignettes.  I am on a NEC 2690.
[a href=\"index.php?act=findpost&pid=176880\"][{POST_SNAPBACK}][/a]

That's due to the 8-bit display (or 8-bit gradient), probably combined with software color management for the monitor.  Software color management posterizes the video.  What you need is to find an option to create gradients with dithering, or add your own noise to the image in 16-bit mode (just a tiny bit).

PS's gradient tool has a dithering option.
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brianchapman

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Banding in photo
« Reply #5 on: February 24, 2008, 11:29:50 pm »

This happens all the time using layer masks (with or without gradients per se) and is usually easy to fix by adding a little noise to the mask (or layer in this case).  

I'm sure John knows more than I do but I've tried the dithering options and have still had to add noise to fix the issue.  

Brian
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Craig Murphy

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Banding in photo
« Reply #6 on: February 28, 2008, 04:04:51 pm »

OK.  Thanks for all the responses.  I'll try the suggestions.
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meierruedi@hotmail.com

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Banding in photo
« Reply #7 on: February 29, 2008, 11:36:26 am »

I had the same issue when creating a new file (16bit) and then applying a black to white gradient: funny "banding" and some colour shifts altough it was black, greys and white.

At the time I tought it had to do with my aging CRT monitor but the same happens with my brand new NEC 2690.....

These files printed looked all right, so maybe it is some kind of monitor/profile issue


The attachment is a screenshot as seen on my Spectraview 2690

?Do people with Eizo/LaCie/Quato displays get the same?

[attachment=5337:attachment]
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eronald

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Banding in photo
« Reply #8 on: February 29, 2008, 03:43:58 pm »

The standard monitor test consists of creating an untagged RGB file with a white to black gradient, and then assigning it the monitor profile; if the monitor is good and decently profiled, the result should be fairly smooth. Doing the test with an sRGB or Adobe RGB file might sound smarter and yields information about the whole system including PS but is not especially informative about the monitor.

Edmund




Quote
I had the same issue when creating a new file (16bit) and then applying a black to white gradient: funny "banding" and some colour shifts altough it was black, greys and white.

At the time I tought it had to do with my aging CRT monitor but the same happens with my brand new NEC 2690.....

These files printed looked all right, so maybe it is some kind of monitor/profile issue
The attachment is a screenshot as seen on my Spectraview 2690

?Do people with Eizo/LaCie/Quato displays get the same?

[attachment=5337:attachment]
[a href=\"index.php?act=findpost&pid=178238\"][{POST_SNAPBACK}][/a]
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Panopeeper

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Banding in photo
« Reply #9 on: February 29, 2008, 03:47:30 pm »

Is this a photo, because it has been created by Photoshop?
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Gabor

David Barr

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Banding in photo
« Reply #10 on: February 29, 2008, 10:57:55 pm »

Quote
Can anyone tell me what is causing the circular bands you see in this image?  It was created by filling a new file with green, then on a new layer with a darker green, then punching a hole for the center spotlight look.   I have seen this happen with other images when attempting vignettes.  I am on a NEC 2690.
[a href=\"index.php?act=findpost&pid=176880\"][{POST_SNAPBACK}][/a]


Craig I downloaded your file and opened it in Photoshop.  If you turn on gamma warning you can see the banding very clearly.  I known that the gamma warning is to show what will happen in print but I believe it is part of the same problem if you are using colors that won't reproduce on screen then you can't get a smooth gradient.  

You might want to try "building your file again using colors that are monitor compatible.  Rather than use the Photoshop color picker go into the color libraries and choose something like DIC color guide colors which seem to stay in gamma.

Also you might try to build your centre spotlight look by filling the file with your background color and using radial tool/ radial gradient to give your the effect you are after.

My 2ยข
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