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Author Topic: Banding in Photoshop  (Read 1728 times)

Phil Corley

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Banding in Photoshop
« on: February 12, 2017, 02:16:55 PM »

Just noticed this; when editing in Photoshop CC using a number of adjustment layers, I seem to get banding on the display.  If I zoom to 100% or Merge Visible layers into one layer the banding goes away

This is on an iMac 27" 5k which has been profiled with I1 Display Pro

Any idea what causes this and how to cure it ?

Thanks

Phil
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Jim Kasson

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Re: Banding in Photoshop
« Reply #1 on: February 12, 2017, 04:35:00 PM »

Just noticed this; when editing in Photoshop CC using a number of adjustment layers, I seem to get banding on the display.  If I zoom to 100% or Merge Visible layers into one layer the banding goes away

This is on an iMac 27" 5k which has been profiled with I1 Display Pro

Any idea what causes this and how to cure it ?

Thanks

Phil

I've seen that happen because of aliasing in Ps's rezzing down the file for display on the screen. Unless you want to remove high-frequency components from the file (definitely not recommended) nothing to be done about it.  If merge visible cures it at the same screen view, it's more complicated than that.

Jim

BobShaw

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Re: Banding in Photoshop
« Reply #2 on: February 12, 2017, 06:08:31 PM »

Is your image mode 16bit? If not try that
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kers

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Re: Banding in Photoshop
« Reply #3 on: February 12, 2017, 08:44:38 PM »

16 bit images for one and if you flatten the image it will be gone usually.

It can be Photoshop to screen translation that is not real. But it can be real; measure the numbers to see if they jump.

if you print your image it can happen again but different, than caused by the translation to the printer and its capabilities.

perfection is always a difficult thing.

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CeeVee

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Re: Banding in Photoshop
« Reply #4 on: February 12, 2017, 08:59:14 PM »

I have seen this many times with images that have been "pushed" too far.
Look for a "comb" in the histogram. The data has been stretched too far and the banding will show on screen or in prints. If there's a way to average out the data in this event I haven't found it yet.

Sent from my SAMSUNG-SM-N900A using Tapatalk

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nirpat89

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Re: Banding in Photoshop
« Reply #5 on: February 13, 2017, 01:38:11 AM »

I have seen banding in cases where color changes are extreme, like an intense clear dawn sky - even without any added post-processing.  Drove me crazy the first time I encountered it.  I almost stopped taking dawn pictures because of that. 

In the case where it was not present in the original raw file but showed up after adding layers, the first line of defense is what you have already done, i.e. flatten the layers.  To do so non-destructively, you can simple make a new merge layer on top of the individual layers which you will still have access to later.  If this merging takes care of the banding then the problem is related to how Photoshop approximates the effect of each layer but not intrinsic to the final file.  If you still see banding after merging the layers, you can try converting your final file to a 8-bit one which will introduce dithering that could help as well.  Same result if you convert to jpeg. 

If none of this works or it shows up in the print, then introduce noise (filter>noise>add noise) in the problem area on the above-mentioned merge layer (making it a smart layer would allow you to play with amount.)  In my experience 2-4% noise levels dramatically alleviated the banding.  If still not good enough, desaturate the colors.  Or as I did in one of my most egregious case, covert it to black and white and pretend like that was what you wanted to do all along :).
« Last Edit: February 13, 2017, 01:49:48 AM by nirpat89 »
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Phil Corley

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Re: Banding in Photoshop
« Reply #6 on: February 13, 2017, 02:56:48 PM »

Thanks guys; it must be the way Photoshop is handling the layers on the 5k screen (I think!)

They are 16 bit files, the problem happens mostly in skies when a number of layers are in use, and is fixed by zooming into 100% - it goes but comes back when fitting the image to screen; or by flattening the layers.

Not sure if it makes any difference, but these are large files > 1.5gb (a number of layers with MF digital files from a Pentax 645z).

Suppose I have to live with it.

Or get another screen - would that help ?

Thanks

Phil
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paulster

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Re: Banding in Photoshop
« Reply #7 on: February 13, 2017, 03:02:03 PM »

What colour space are you using? There is a bug if you use ProPhoto RGB and have hardware acceleration enabled that I've been trying to get Adobe to take seriously for a couple of years now. This particular one doesn't go away at 100%, but it's typically more obvious at lower zoom levels.
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kers

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Re: Banding in Photoshop
« Reply #8 on: February 13, 2017, 03:33:01 PM »

...and is fixed by zooming into 100% -...
Phil

i forgot : 100% is the best view ( most straightforward)  then 50% and 25 % etc.
do you still see the banding in 100% flattened images?
then start measuring. ( 1 pixels size measure) to see if it is real.
it is one of the basic problems of working digital since everything is cut into hard blocks with one color.

Blue skies par example that gradually change color are easy victims for mostly one color channel (Blue) is used.

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Jim Kasson

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Re: Banding in Photoshop
« Reply #9 on: February 13, 2017, 03:37:39 PM »

Thanks guys; it must be the way Photoshop is handling the layers on the 5k screen (I think!)

They are 16 bit files, the problem happens mostly in skies when a number of layers are in use, and is fixed by zooming into 100% - it goes but comes back when fitting the image to screen; or by flattening the layers.

Not sure if it makes any difference, but these are large files > 1.5gb (a number of layers with MF digital files from a Pentax 645z).

Suppose I have to live with it.

Or get another screen - would that help ?

Thanks

Phil

If it is resampling for screen, one way for Ps to fix (most of) the problem would to be smarter about their resampling algorithm. That would probably slow the program down, thought. It may also be that Ps takes shortcuts on layer handling for fast screen preview, possibly doing the calcs in 8-pit precision. One way for Adobe to deal with both of those things without affecting performance all the time would be to have a recalculate button similar to what they already have for 15+bit histograms.

Jim

Jim Kasson

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Re: Banding in Photoshop
« Reply #10 on: February 13, 2017, 03:40:49 PM »

i forgot : 100% is the best view ( most straightforward)  then 50% and 25 % etc.
do you still see the banding in 100% flattened images?
then start measuring. ( 1 pixels size measure) to see if it is real.
it is one of the basic problems of working digital since everything is cut into hard blocks with one color.

Blue skies par example that gradually change color are easy victims for mostly one color channel (Blue) is used.

Outside of intentional abuse for testing purposes I have not seen banding in edited files due to inadequate precision with Ps using 15+ bit mode. Of course, this used to occur all the time with 8-bit precision, but those days are -- thankfully -- over.

Jim

Doug Gray

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Re: Banding in Photoshop
« Reply #11 on: February 14, 2017, 02:53:14 PM »

I have a 10 bit per channel monitor and PS CC does not always use 10 bits. It sometimes reverts to 8 bits depending on certain settings.  It might be worth experimenting in the following areas where I have seen the variation:

1. Enabling or disabling the graphics acceleration.
2. Changing the Desaturate Colors check box but keeping the percentage at 0%.

These settings affect the way the PS color rendering engine runs. In particular the soft proofing at low luminance levers and the bits of resolution that goes to the monitor at all luminance levels.

However, this in on a Windows machine so PS may operate differently with other OSes or even different display adapter tech.
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BobShaw

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Re: Banding in Photoshop
« Reply #12 on: February 14, 2017, 03:40:14 PM »

They are 16 bit files, .....
Yes, but are you working in 16 bit mode.
Go Image > Mode > 16 bits per channel
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Jim Kasson

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Re: Banding in Photoshop
« Reply #13 on: February 14, 2017, 03:59:15 PM »

I have a 10 bit per channel monitor and PS CC does not always use 10 bits. It sometimes reverts to 8 bits depending on certain settings.  It might be worth experimenting in the following areas where I have seen the variation:

1. Enabling or disabling the graphics acceleration.
2. Changing the Desaturate Colors check box but keeping the percentage at 0%.

These settings affect the way the PS color rendering engine runs. In particular the soft proofing at low luminance levers and the bits of resolution that goes to the monitor at all luminance levels.

However, this in on a Windows machine so PS may operate differently with other OSes or even different display adapter tech.

I don't know why Ps doesn't do error diffusion with 8-bit graphics subsystems. If performance is an issue, it could do it "lazily", in the background.

Jim

Doug Gray

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Re: Banding in Photoshop
« Reply #14 on: February 14, 2017, 04:29:09 PM »

I don't know why Ps doesn't do error diffusion with 8-bit graphics subsystems. If performance is an issue, it could do it "lazily", in the background.

Jim

I don't know either but I vaguely recall that some graphics card drivers would do this. Would work quite well at the pixel level because the localized color differences are not discernible. 
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Jim Kasson

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Re: Banding in Photoshop
« Reply #15 on: February 14, 2017, 04:41:19 PM »

I don't know either but I vaguely recall that some graphics card drivers would do this. Would work quite well at the pixel level because the localized color differences are not discernible.

Agreed. Heck, it even worked well with the old "16-bit" (5/6/5) displays.

Jim

Phil Corley

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Re: Banding in Photoshop
« Reply #16 on: February 14, 2017, 05:10:16 PM »

Hi Bob

Yes, working in 16bits per channel.

Yes, but are you working in 16 bit mode.
Go Image > Mode > 16 bits per channel
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