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Author Topic: Math Behind PS Blend Modes  (Read 1943 times)
fike
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« on: March 11, 2013, 04:16:11 PM »
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I have always had a hard time UNDERSTANDING what each blend mode is actually doing and how it works. As a result, I find myself iterating through many different blend modes to find one that does what I want.

Does anyone know if there is a resource that describes mathematically how each blend mode combines one simple layer with the one below it?

Regards,
Marc
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Fike, Trailpixie, or Marc Shaffer
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I carry an M43 ILC, a couple of good lenses, and a tripod.
opgr
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« Reply #1 on: March 11, 2013, 05:00:31 PM »
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Oddly enough you can find the formulas in the Adobe PDF specs, chapter 11, page 324, table 136

Be aware though that formulas have a tendency to mess with your creativity...
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Oscar Rysdyk
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Vladimirovich
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« Reply #2 on: March 11, 2013, 05:00:57 PM »
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http://zhur74.livejournal.com/  -> (use translate.google.com) ->


http://zhur74.livejournal.com/6298.html ( how to study )

http://zhur74.livejournal.com/6988.html ( Darken и Lighten )

http://zhur74.livejournal.com/8181.html ( Multiply и Screen )

http://zhur74.livejournal.com/9582.html ( Color Burn и Color Dodge )

http://zhur74.livejournal.com/10973.html ( Linear Burn и Linear Dodge )

http://zhur74.livejournal.com/14839.html ( Overlay и Soft Light )

http://zhur74.livejournal.com/15544.html ( Hard Light, Vivid Light, Linear Light, Pin Light )

http://zhur74.livejournal.com/17188.html ( Hard Mix, Difference, Exclusion )

http://zhur74.livejournal.com/17811.html ( Darker Color, Lighter Сolor, Dissolve )

http://zhur74.livejournal.com/20578.html ( Hue, Saturation, Color и Luminosity )

http://zhur74.livejournal.com/21254.html ( Luminosity )

http://zhur74.livejournal.com/30090.html ( brief summary )

« Last Edit: March 11, 2013, 05:05:22 PM by Vladimirovich » Logged
Schewe
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« Reply #3 on: March 11, 2013, 05:21:41 PM »
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I have always had a hard time UNDERSTANDING what each blend mode is actually doing and how it works. As a result, I find myself iterating through many different blend modes to find one that does what I want.

Careful what you wish for...understanding the math may not actually help you understand the aesthetic of using them. In general, for photo imaging, the basic ones such as screen & multiply, lighten and darken should be pretty easy to figure out. Overlay is a procedural blend of screen above 127 and multiply below 127 (middle gray does nothing). The others such as Luminosity, Color, Hue and Saturation should be self describing...

I think the better question (or questions) are what are the various blend modes good for. I really have no use for those other than what I've already mentioned...the others not mention may have some useful technical or mathematic use...but I don't find any use for digital photo imaging...
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fike
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« Reply #4 on: March 11, 2013, 05:58:38 PM »
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Careful what you wish for...understanding the math may not actually help you understand the aesthetic of using them. In general, for photo imaging, the basic ones such as screen & multiply, lighten and darken should be pretty easy to figure out. Overlay is a procedural blend of screen above 127 and multiply below 127 (middle gray does nothing). The others such as Luminosity, Color, Hue and Saturation should be self describing...

I think the better question (or questions) are what are the various blend modes good for. I really have no use for those other than what I've already mentioned...the others not mention may have some useful technical or mathematic use...but I don't find any use for digital photo imaging...

Understood. I agree, but I learned one or two interesting things by looking at Opgr's link from above:
http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/pdf/pdfs/PDF32000_2008.pdf#page=331

1) blending layers behave differently in a different color mode. I will need to experiment with this.
2) blending layers can be used to target only lighter or darker regions. I spend a lot of time with elaborate masking tactics to target certain ranges of luminosity or colors. Now I understand better how I can use lighten and darken blend modes.
3) I hadn't thought of using mostly blank layers with blend mode set to multiply, color burn, or color dodge and then painting in the blend mode effect with brushes--black or white, or a color I want to emphasize or de-emphasize. 

In the past, my use of blend modes was mostly reserved to lighten for layered long exposure star shots, hard light for local contrast enhancement with a high-pass filter, and difference blending mode for finding the best seams when manually blending panoramics.  What other interesting lessons about blend modes have I missed?
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Fike, Trailpixie, or Marc Shaffer
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Schewe
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« Reply #5 on: March 11, 2013, 06:42:01 PM »
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What other interesting lessons about blend modes have I missed?

What about the Blend If sliders in the Layer Style dialog...combined with blend modes, blend if (if you use the option/alt keys to split the sliders) allow a lot of specific blend targeting...pretty powerful.
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Jim Kasson
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« Reply #6 on: March 11, 2013, 07:48:56 PM »
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Be aware though that formulas have a tendency to mess with your creativity...

Then I'm in real trouble. I've lately been trying to make art without an image editor at all, but by writing code instead. Unfortunately, what I've done so far (like this) doesn't look good at web resolution. I'm hoping that the right and left brains can coexist in harmony.

Jim
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MarkH2
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« Reply #7 on: March 11, 2013, 09:41:44 PM »
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Does anyone know if there is a resource that describes mathematically how each blend mode combines one simple layer with the one below it?


The clearest explanation, including the math, I have ever found is a terrific article by Robert Thomas, "Photoshop Blend Modes Explained" at http://photoblogstop.com/photoshop/photoshop-blend-modes-explained

Includes "Blend If" luminance blending.
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snoleoprd
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« Reply #8 on: March 12, 2013, 10:23:14 AM »
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The clearest explanation, including the math, I have ever found is a terrific article by Robert Thomas, "Photoshop Blend Modes Explained" at http://photoblogstop.com/photoshop/photoshop-blend-modes-explained

Includes "Blend If" luminance blending.


I have to agree this is the best and easiest to understand explanation, I was about to post it as well.  Grin

Alan
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Alan Smallbone
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« Reply #9 on: March 12, 2013, 12:07:26 PM »
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The clearest explanation, including the math, I have ever found is a terrific article by Robert Thomas, "Photoshop Blend Modes Explained" at http://photoblogstop.com/photoshop/photoshop-blend-modes-explained

Includes "Blend If" luminance blending.


Excellent resource. Bookmarked.  Thank you VERY much for the link.
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MarkH2
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« Reply #10 on: March 12, 2013, 12:31:46 PM »
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You are welcome.  I suspect this article is not as well known as it deserves to be, IMHO, and clearly Alan's as well.
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Guillermo Luijk
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« Reply #11 on: March 14, 2013, 09:47:59 AM »
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Clear and rigurous formula explanation: How do Adobe Photoshop, Micrografx PicturePublisher and Pegtop XFader blend layers?
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Jim Kasson
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« Reply #12 on: March 14, 2013, 10:04:10 AM »
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...Micrografx PicturePublisher...

Oh, the memories! And not all of them good.

Jim
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