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Difference layer mask

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  #21  
Old 04-11-2011, 05:40 PM
Flashtones Flashtones is online now
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Re: Difference layer mask

I've not read all the links in this thread, and maybe I'm way off here, but I always thought of a difference mask as the difference between a luminosity mask and an inverted luminosity mask. IOW, a mid-tones mask.

One can be made without calculations as such.
Go to the channels pallet and CMD+Click the composite channel to select the luminosity.
Hit the new channel button at the bottom of the pallet to create an alpha channel based on this luminosity.
Select the new channel to make it active. The original Luminosity selection should still be active, and now fill that selection with black.

At that point the blacks of your alpha channel should be filled with black (upon creation of the alpha thru the luminosity selection,) and the whites should be filled with black too from filling the still active selection with black. What's left are your midtones - the difference between the luminosity mask and the inverted luminosity mask.

Adjustments made through this mask would primarily affect midtones.

But maybe I'm misinterpreting.
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  #22  
Old 04-11-2011, 06:12 PM
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Boneappetit Boneappetit is offline
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Re: Difference layer mask

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Originally Posted by mistermonday View Post
Yes, that would work but wouldn't it be more efficient to just create a merge all layer and select the luminosity and hit the Create mask button?
Regards, Murray
That's exactly my point Murray... Julian, I created an Action using these simple steps, just what Natalia posted earlier... So now I can see it is just a matter of how Mr. Randall calls that... No wonder why we cannot find any info. under the term "Difference Mask", it is just a Luminosity Mask under a Difference blend mode... Thanx for pointing this out Murray...
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  #23  
Old 04-11-2011, 06:16 PM
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Boneappetit Boneappetit is offline
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Re: Difference layer mask

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Originally Posted by Flashtones View Post

Adjustments made through this mask would primarily affect midtones.

But maybe I'm misinterpreting.
Darn right Flashtones, it affects midtones...
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  #24  
Old 04-11-2011, 06:17 PM
julianmarsalis julianmarsalis is offline
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Re: Difference layer mask

Quote:
Originally Posted by Flashtones View Post
I've not read all the links in this thread, and maybe I'm way off here, but I always thought of a difference mask as the difference between a luminosity mask and an inverted luminosity mask. IOW, a mid-tones mask.

One can be made without calculations as such.
Go to the channels pallet and CMD+Click the composite channel to select the luminosity.
Hit the new channel button at the bottom of the pallet to create an alpha channel based on this luminosity.
Select the new channel to make it active. The original Luminosity selection should still be active, and now fill that selection with black.

At that point the blacks of your alpha channel should be filled with black (upon creation of the alpha thru the luminosity selection,) and the whites should be filled with black too from filling the still active selection with black. What's left are your midtones - the difference between the luminosity mask and the inverted luminosity mask.

Adjustments made through this mask would primarily affect midtones.

But maybe I'm misinterpreting.
I think we may have a winner here basically it was for adjusting midtones.

Per Mr Randall

Load it to make it active, and then ask for a layer curve. Now you can play with adding or detracting density from the midtone area to help create the illusion of more density. Usually this is a darkening move, but it can go the other way too. / ------

Thanks Fleshtones that clears that up most excellent...
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  #25  
Old 04-11-2011, 06:49 PM
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Boneappetit Boneappetit is offline
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Re: Difference layer mask

Quote:
Originally Posted by julianmarsalis View Post
I think we may have a winner here basically it was for adjusting midtones.

Per Mr Randall

Load it to make it active, and then ask for a layer curve. Now you can play with adding or detracting density from the midtone area to help create the illusion of more density. Usually this is a darkening move, but it can go the other way too. / ------

Thanks Fleshtones that clears that up most excellent...


Julian: I think that's not the Difference Mode, that's more like the tangent mode, LOL...
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  #26  
Old 04-11-2011, 07:08 PM
Flashtones Flashtones is online now
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Re: Difference layer mask

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Originally Posted by Boneappetit View Post
That's exactly my point Murray... Julian, I created an Action using these simple steps, just what Natalia posted earlier... So now I can see it is just a matter of how Mr. Randall calls that... No wonder why we cannot find any info. under the term "Difference Mask", it is just a Luminosity Mask under a Difference blend mode... Thanx for pointing this out Murray...

But a stamped merge layer in difference mode over the file that created it would yield zero difference, or a fully black mask, no?

Which begs the question, what is the "difference" one is trying to find/effect?

I don't think the purpose it to find the difference between two images (to what effect?), it's to find an area of luminosity within one image.
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  #27  
Old 04-11-2011, 07:13 PM
julianmarsalis julianmarsalis is offline
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Re: Difference layer mask

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Originally Posted by Boneappetit View Post
Julian: I think that's not the Difference Mode, that's more like the tangent mode, LOL...
Bone its not a mode its a mask your creating to just effect midtones with a curve layer lol key pt from Mr Randall is and then ask for a layer curve. Now you can play with adding or detracting density from the midtone area to help create the illusion of more density. Usually this is a darkening move, but it can go the other way too.


Its not a mode its a type of mask you use on a curves layer a difference mask >.>. I have the picture somewhere printed out lol...
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  #28  
Old 04-11-2011, 07:15 PM
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mistermonday mistermonday is offline
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Re: Difference layer mask

Quote:
Originally Posted by Flashtones View Post
I've not read all the links in this thread, and maybe I'm way off here, but I always thought of a difference mask as the difference between a luminosity mask and an inverted luminosity mask. IOW, a mid-tones mask.

One can be made without calculations as such.
Go to the channels pallet and CMD+Click the composite channel to select the luminosity.
Hit the new channel button at the bottom of the pallet to create an alpha channel based on this luminosity.
Select the new channel to make it active. The original Luminosity selection should still be active, and now fill that selection with black.

At that point the blacks of your alpha channel should be filled with black (upon creation of the alpha thru the luminosity selection,) and the whites should be filled with black too from filling the still active selection with black. What's left are your midtones - the difference between the luminosity mask and the inverted luminosity mask.

Adjustments made through this mask would primarily affect midtones.

But maybe I'm misinterpreting.
Hi Flashtones, what you have generated is known by me as a midtone mask. It can also be generated by Select>Color Range and select Mid Tones from the pull down menu.
To me a difference mask has always been a mask created to isolate fine differences between two almost identical layers and those differences are more often not in midtones. One example where I use it is to make a very precise selection using a Hue/Sat adj layer. A Hue/Sat adj can actually isolate certain pixels in a manner that can not be achieved with Selective Color or Magic Wand, or other tools. The problem is that Hue/Sat will not allow you to make a selection from the pixels that it is affecting. Setting the layer to Difference Blend mode and making a mask of the difference does the job.
Regards, Murray
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  #29  
Old 04-11-2011, 07:17 PM
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Boneappetit Boneappetit is offline
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Re: Difference layer mask

Quote:
Originally Posted by Flashtones View Post
But a stamped merge layer in difference mode over the file that created it would yield zero difference, or a fully black mask, no?

Which begs the question, what is the "difference" one is trying to find/effect?

I don't think the purpose it to find the difference between two images (to what effect?), it's to find an area of luminosity within one image.
Yes, if you apply the Difference Mode directly on the stamped layer, first we need to select the Luminosity mask, create it and then apply the DBM...
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  #30  
Old 04-11-2011, 07:22 PM
julianmarsalis julianmarsalis is offline
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Re: Difference layer mask

Quote:
Originally Posted by mistermonday View Post
Hi Flashtones, what you have generated is known by me as a midtone mask. It can also be generated by Select>Color Range and select Mid Tones from the pull down menu.
To me a difference mask has always been a mask created to isolate fine differences between two almost identical layers and those differences are more often not in midtones. One example where I use it is to make a very precise selection using a Hue/Sat adj layer. A Hue/Sat adj can actually isolate certain pixels in a manner that can not be achieved with Selective Color or Magic Wand, or other tools. The problem is that Hue/Sat will not allow you to make a selection from the pixels that it is affecting. Setting the layer to Difference Blend mode and making a mask of the difference does the job.
Regards, Murray
Robert talked about the limits of using select color...

Quote:
Originally Posted by Robert Randall
Quote:
Originally Posted by Ronald N Tan
Hiya Bob,

Some of the techniques and tips are being done in my images similar to yours sir. Earlier in the thread, I provided my thoughts in channel pulling and I mentioned that although these procedures are traditionally associated with masking and composition, I utilized them towards manipulating tone and contrast.

Highlight masking and shadow masking, which are available under the Select Color ( I think) I've done some cool things with them too.

But....

I have yet to try the different mask from your procedure. =) That sir, is what I plan to play with. =)
Are you talking about using Color Range as a tool to create masks? You might find that creating masks by using apply several times in multiply gives you a smoother transition than a mask created using color range parameters.
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