Comments on: How to express blend modes as curves http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/ The latest news about the top pixel wrangling application on the planet. Sat, 25 May 2013 08:41:56 +0000 hourly 1 http://wordpress.org/?v=3.5.1 By: vittiphoto http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-13211 vittiphoto Mon, 17 Nov 2008 21:26:05 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-13211 Dear Martin,

Great article, learned much about the math behind Adobe xfer functions.

scenario, I find Curves > Auto is usually pretty accurate, but find myself modifying the auto changes, reducing them. Is simply applying a Curves adjustment layer at 50% equivalent to halving the RGB moves made by the Curves > Auto function?

TIA,

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By: Martin Evening http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12176 Martin Evening Fri, 05 Oct 2007 06:06:23 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12176 But Tone Curves aren’t so straight forward in Lightroom either!

See: http://lightroom-news.com/2007/10/04/lightroom-versus-photoshop-curves/

Martin

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By: photoshop-user http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12159 photoshop-user Fri, 28 Sep 2007 18:29:15 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12159 i really have to say, thank god for Photoshop Lightroom!

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By: arne http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12150 arne Wed, 26 Sep 2007 22:26:03 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12150 Martin, I’m highly interested in your results. Please send me an email if you got any further. Thanks

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By: ThaGangsta http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12144 ThaGangsta Mon, 24 Sep 2007 20:43:31 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12144 woooow, this is the most weird thing I’ve learned for Photoshop so far :) ..thank you for the knowledge, sir :)

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By: Martin Evening http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12139 Martin Evening Sat, 22 Sep 2007 21:45:12 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12139 Sorry for the delay responding folks – I have been away on holiday for a couple weeks.

Arne,

I wish I knew the full answer here. My assumption is that a normal curve is like a bezier curve that uses mathematical expressions to describe the shape of the curve and therefore requires no interpolation to calculate the transformation of the levels at all points of the curve.

When you switch to arbitrary map mode, the curve is controlled by 256 discrete curve points rather than a pure mathematical description and this is where interpolation has to be used to calculate the in-between values. How Photoshop translates between the two curve modes I don’t know. You raise an interesting question though. Can you create an .amp curve setting, switch to the normal point curve mode and save the setting out as a .crv setting? If you loaded .crv setting versions for the curves, would they be different to the .amp curves? Would you see a more precise match at 16-bit? I should give this a test.

Martin

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By: gamini http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12129 gamini Wed, 19 Sep 2007 17:58:53 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12129 Martin..I like your books and this tutorial is brilliant !

I totally agree with Andrew Rodney regarding “Photoshop gurus” who come up with all these strange esoteric steps (some as long as 55 steps) to do something when you can do the exact same thing in one or two simple steps.

Remember Einstein said of Jean Piaget’s work “so simple that only a genius could have thought of it.”

http://gamini.org

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By: Andrew Rodney http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12105 Andrew Rodney Tue, 11 Sep 2007 17:13:36 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12105 [quote]As far as some people are concerned, Photoshop holds a certain mystique where it is assumed that a more complex approach will produce a more refined result. But very often the underlying math is the same as that used when applying a simpler approach. [/quote]

This is the most useful statement about imaging process I’ve heard in a long time. I’m so sick and tired of some so called Photoshop guru’s who try to be macho and make a 48 step process in order to make the user think its worthwhile due to all the steps. If only all Photoshop instructors used their head, as Martin has done here to illustrate this isn’t so. If I had a dime for all the presentations and tips I’ve read that DON’T follow this KISS rule, I’d retire. Thanks Martin. While the tips here are superb, the theory expressed is equally important for Photoshop users.

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By: 01af http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12099 01af Mon, 10 Sep 2007 13:37:33 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12099 Wow! If reading this blog doesn’t turn us into Photoshop experts then I don’t know what …!

Of course, representing blending modes as 256 x 1 pixel grayscale images (and consequently, as curves) works only because we are blending one image into itself. Is there also a method to represent the blending of *two* images as a grayscale image? It would be a 256 x 256 pixel image rather than 256 x 1. It would be nice to be able to create new custom blend modes this way …

And where can I see the formulas for all the blend modes? I already know the formulas for Normal, Multiply, Screen, and Difference as those are simple enough. I’d like to know the others, too.

– Olaf

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By: arne http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12098 arne Mon, 10 Sep 2007 12:49:13 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12098 Martin, it worked exactly as you described. Though I’m getting spikes in the histogram with the applied curve, possibly due to the interpolations between the 256 values, there is no posterisation visible to me whatsoever. I just wonder: How is it possible that the interpolation is so “primitively linear”. Shouldn’t the imported amp-file automatically be transformed into a smooth spline curve, when you click the “Edit Points” button in the curves dialog? At least it appears to me that if you do so and edit one point just slightly, you can go back to “draw curve” and the dotted curve is smooth like a spline… though it does not change my spiked histogram.
But maybe this is just nit picking :-)

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By: Jann Lipka http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12086 Jann Lipka Sat, 08 Sep 2007 07:54:56 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12086 Thanks a lot for very interesting adjustment approach !
Very smart .raw workaraound , that sounds so usefull !

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By: Martin Evening http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12083 Martin Evening Fri, 07 Sep 2007 08:20:19 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12083 Davide,
I would say not, since the blend modes you mentioned (Luminosity and Lighten) are, like all blend modes, formulas used to calculate the resulting tone adjustment. The article points out that certain of these blend modes, such as Screen, Multiply, Overlay and soft light can effecively be summarised as curves and produce an identical processed result at 8-bit. With the other blend modes you can in some cases use the steps to create a tone curve setting, but you cannot replicate the exact effect with a tone curve alone. So for example, a Luminosity adjustment is filtering out the effect a tone adjustment has on the colour component. As you already know, you end up targeting the luminance only. The same with Lighten, you are applying a formula that is based on the image content.

I would say stick with the technique you are already using and the only refinement I can suggest is to record the steps you use as an Action in order to apply this quickly.

Martin

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By: unDavide http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12079 unDavide Thu, 06 Sep 2007 19:45:05 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12079 Martin,
I used to use two clipped adjustment layers (a multiply clipped to a luminosity, for instance) to retain only the desired effect (darker without any color/saturation shift in the previous example) Playing around with this led me to interesting effects (soft light on lighten, etc). Do you think your technique would work with these “composite” use of blending modes?
Best regards and thanks for your enlightening article!

Davide Barranca

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By: Martin Evening http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12078 Martin Evening Thu, 06 Sep 2007 15:16:40 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12078 When you open the Photoshop raw file, set the Channel count to 3 and uncheck the Interleaved option. This will open the image up as an RGB file in the default RGB workspace. You can then edit the individual channels and save as an.amp setting and then try loading as a preset.

From what I can see this could work in colour, but I have not got around to testing how well it would work. If you try this out, let me know how you get on.

Martin

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By: arne http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/comment-page-1/#comment-12077 arne Thu, 06 Sep 2007 13:19:50 +0000 http://photoshopnews.com/2007/09/05/how-to-express-blend-modes-as-curves/#comment-12077 Seriously this is one of the best tip and Photoshop insight I’ve ever heard of! Thank you so much for your article!
I was just wondering if there is a way how one could use this technique also in RGB mode? This would be handy i.e. for simulating film color responses with curves. I could imagine that this will work, if one switches to rgb mode and then saves each color channel in a separate grayscale raw file. But then again: How does one load this three amp files into one curve adjustment layer? Maybe you have an idea.

Thanks,
Arne

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