Difference Blend problem.

[JPvanR]

Hi.
I have no idea wether this specific problem has been adressed before or not. I did a quick search but couldn't find anything really relevant.

Here goes: when using a layer with blending mode set to difference in a multi layered document in order to change colours,
these colours are not interpreted correctly when saving or merging the document. (If necessary I can show an example.)
Did anyone ever encounter the same problem?
Did he or she find a solution/workaround?
Is it.... tatataaa... a bug?

I'd love to know, because it is very annoying.

Kind regards

Jean-Pierre van Rumste
Belgium

[davescm]

No bug here with difference blend mode but :

1. Make sure you are viewing the blend at 100% zoom. At zoom levels less than 66.7%,  8 bit previews are used to draw the screen blend- not the full image data. That can lead to some differences when merging. So the accurate preview is always the 100% zoom..

2. Some blending is now done on the GPU and can lead to issues if the GPU driver is buggy. Try going to Preferences > Performance and check "Legacy Compositing". Then close and restart Photoshop.

Dave

[JPvanR]

I can look at whatever zoom percentage I want, the problem is consistent at each and every one of them and has nothing to do with viewing. The problem occurs when merging or saving. Then all of a sudden the color changes due tot difference blending mode being either misinterpreted or simply ignored. I'm not sure which one. 
I use an NVidia GTX 970M with an Eizo monitor. Never had any problems.

[davescm]

If it is neither of the above then please post a link to an example file which shows the issue you describe. I'll try it here.

Dave

[JPvanR]

A couple of screenshots( made with Faststone): one before merging (as shown in the layered document), second after merging (ctrl
shift alt E). If you can tell me where I can post a psd file for testing I'd be happy to.

[davescm]

Hi

Well I can definitely see a difference in the screenshots.

You can upload to dropbox (or similar) and share a link or even to your CC Cloud and share a link from there

Dave

[JPvanR]

Hi Dave.
If I figured this out right you should be able to find a PSD file here:
Adobe Creative Cloud

Hope that works.

[davescm]

Hi

To share from Create Cloud click on the three dots

Then on Share

Set "Allow download"  then click "Copy Link"

Paste the link here

Dave

[JPvanR]

https://adobe.ly/2IXkNkc

[JPvanR]

Hopefully the above works.

[davescm]

The problem is exactly what I said in my earlier post (post #1)

No merging full layer stack still in place :

1. Screenshot 50% zoom (which uses 8 bit previews to blend):

2. Screenshot at 66.7% or greater zoom - which is blended using full 16 bit image data

You must check blending at 100% zoom.

Dave

[Chuck Uebele]

I'm getting the same issue with your file. Very odd.

[Myra Ferguson]

Dave is right. If you go to Image > Mode, change it to 8 bits/channel, and then merge, then the reddish color stays.

[davescm]

This is not a bug*. It is just tbe way Photoshop works and always has worked since the introduction of 16 bit capability. I understand it was done to speed up redraw and in most images makes no visible difference. However with certain images the difference can be dramatic.

Given the faster processing available from modern GPUs it would be nice if the zoomed out versions were done in full 16 bit, however until then the advice is always zoom in and check your blending at 100%

Dave

Edit : See later post. Although there are normall differences seen in blending between 8 and 16 bit, there may also be a specific bug involved in the way opacity and fill interact in difference blend mode between 8bit and 16 bit)

[Chuck Uebele]

Dave, Even with your explanation, this seems odd. Why the dramatic shift with 16 bit? If using 8 bit, this doesn't happen, and you get the composite view of the zoomed out version of 16 bit. Seems like a bug that 16 bit and 8 bit do not blend the same.

[davescm]

Hi Chuck

I've seen it before when a combination of blends and layer styles is used. The cumulative effect can be quite dramatic but I'll do a bit more digging in this file

Dave

[Chuck Uebele]

Dave, I created it with a other file, just to make sure that it wasn't a corrupted file. Just doesn't seem right that there is such a drastic difference with 16 bit. Do you know if this has been reported?

[davescm]

Hi Chuck

I've had a bit more dig and can replicate - but with more detail.

There are a few blend modes where applying Opacity 100% and Fill 65% looks different to Opacity 65% and Fill 100%. It has always been that way and applies to Linear Dodge, Vivid Light, Hard Mix, Color Dodge, Color Burn, Lighter Color and Difference

but....

With Difference it appears that reversing Opacity and Fill make the file look different (as expected?) in 8 bit but reversing them in 16 bit makes no difference - they look the same.

That has the knock on effect (as in the OP file) that when the Opacity is 100% and the Fill is 65% then the blend result changes when switching from 8 bit to 16 bit or vice versa.

Dave

[davescm]

I've raised it as a bug here (and unmarked my previous answer as "correct"):

Difference blend mode change from 8 bit to 16 bit | Photoshop Family Customer Community

Dave

[Chuck Uebele]

Thanks, Dave.

[JPvanR]

Well. OK. That's solved then. Still weird that it doesn't save correctly either!
And also not very nice of the adobe people to NOT mention this. (Unless of course you read through the entire help section probably, but I wonder who does that.

Anyway. A conversion to 8 bit solves the saving problem as wel.
Thnx for the time and willingness to help.
I consider my question answered.

Kind regards
Jean-Pierre van Rumste

[sylwesterł78733104]

I encountered the same problem - Dirrefence blending works different in 8-bit and in 16/32-bit mode.

Difference is one of the 8 special belnding modes, which means it renders different result when adjusting Fill and Opacity.

And it seems Difference is treated as "special" for 8-bit mode, and as "normal" in 16/32 bit modes. I'm not sure it it is bug or a feature....