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Image Processingvalue study - blend if

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PietFrancke
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value study - blend if

Post by PietFrancke » Fri Jan 25, 2019 2:13 am

I got back to reading an old book - the Art of Responsive Drawing by Nathan Goldstein -- An interesting quote within:

"In drawings that concentrate accurately but exclusively on the effects of light, texture, and atmosphere, a sense of volume similar to that in an ordinary snapshot of the subject can result. Such an overemphasis on surface characteristics tends to limit the impression of volume in the same way the photograph does." I think he is saying that too much detail can be detrimental, and that rather we should pick the detail that "helps" and perhaps in some fashion - emphasize that detail.

Anyway, under the premise of "less is more", I wanted to do a value study using only (roughly) three tones - Dark, Mid, Light.

So... First I pulled up a photo I had taken a few weeks ago of my hand. I painted out pieces of distracting background. I turned it to Black and White using Viveza. (I wish I hadn't done that, the colors would have helped better identify cheat spots and helps to see what is going on).
img1.jpg
B/W conversion of color photo
Then I created a new color fill layer and filled it with a dark value - probably 8 or 10 percent light. I clicked on the layer and used blend-if on the underlying layer such that the darker areas all took on the color of the dark fill layer.
img2.jpg
darks acquire the dark layer value
And then I repeated the process but add a Mid-Tone layer and used blend-if on the underlying layer.
img3.jpg
mid tones added
And finally added a Light-Tone layer for the brightest places.
img4.jpg
light tones added
What is cool is that you are in control of When/Where the tone changes by using the blend-if slider. And you are in control of the brightness of your given fill layer.

If you are so inclined, please grab a photo and break it into 3 tones (or 2, or 6). And show your starting image and the final simplification.

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Post by Psjunkie » Fri Jan 25, 2019 3:30 am

Yes Piet...blend-if is a wonderful tool, you know you can use it on adjustment layers, filters and so on...it along with "apply image" and "channels" are some of Photoshop's most powerful tools in my opinion.......


Just some paint...
Red in the highlights
Green in the shadows
Blue in the midtones
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Screen Shot 2019-01-24 at 9.52.14 PM.png

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Post by Duck » Fri Jan 25, 2019 8:30 am

This reminds me of a technique I sometimes use to analyze a composition. I wrote a tutorial on it here; "Three tone guide to composition"

This process is more for compositional analysis than what you're describing here but I thought you might be interested in the similarities.
"If you didn't learn something new today, you wasted a day."
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Post by PietFrancke » Fri Jan 25, 2019 12:18 pm

Duck, (EDIT … Whoops! FRANK I mean), I like how your colors showed the curves of the hand in the green areas - showing (amongst other things) perhaps that image would be stronger if the background was a mid tone.

I'm getting better with blend-if, but seldom/never use the channels. Note to self - play with channels! Thank you for that link, I will check it out. (EDIT .. and apply image too - thanks Frank)

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Post by minniev » Fri Jan 25, 2019 9:41 pm

PietFrancke wrote:
Fri Jan 25, 2019 12:18 pm
Duck, (EDIT … Whoops! FRANK I mean), I like how your colors showed the curves of the hand in the green areas - showing (amongst other things) perhaps that image would be stronger if the background was a mid tone.

I'm getting better with blend-if, but seldom/never use the channels. Note to self - play with channels! Thank you for that link, I will check it out. (EDIT .. and apply image too - thanks Frank)
Ya'll have definitely left me far behind. I don't know what you did with which of the many sliders on "blend if" (upper, lower, left, right, split or not). And I don't know what is supposed to happen next, in either Piet's or Frank's examples, and how I'm to use it for what.

I took a regular picture and by adding three different tonality layers, can push some sliders and make some things turn black or white instead of the colors they are supposed to be. But I am clearly missing some key concepts here.

Channels are another enigma, and the luminosity masks that go with them.

I ended up with a hot mess. I could see some effect from the layers with the darks and brights but not from the midtones, except if I pushed the sliders far enough the whole picture would turn tan. Is it because I picked too complicated a picture? Or just because I don't have a clue?
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x (1 of 1).jpg
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Post by Psjunkie » Fri Jan 25, 2019 10:39 pm

moving the underlying layer left(Black) slider to the right blends your effect into the highlights

moving the underlying layer right(White) slider to the left blends your effect into the shadows

holding the option and splitting the sliders makes a smoother transition...

you'll have to figure out how to look at them side by side but in the example you will see the white stripe blend into the highlights of the rock without affecting the shadows.....

I moved the white slider left a bit so you could see the right hand side of the black slider moved all the way right
notice the square is one color..moving the left half of the black slider to the right a bit will even out the color in the square

take your image and brush a white stripe across it..then play with the sliders and see what you get...
toggle the white stripe layer on and off and you will see the difference...it's hard to compare with my example
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Screen Shot 2019-01-25 at 4.21.16 PM.png
Screen Shot 2019-01-25 at 4.24.05 PM.png

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Post by Psjunkie » Fri Jan 25, 2019 10:45 pm

my brain is slow this afternoon...here is the image completed for you to open in a new tab next to your original and be able to see the difference...
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x (1 of 1) psjunkie.jpg

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Post by PietFrancke » Fri Jan 25, 2019 10:54 pm

minniev wrote:
Fri Jan 25, 2019 9:41 pm
PietFrancke wrote:
Fri Jan 25, 2019 12:18 pm
Duck, (EDIT … Whoops! FRANK I mean), I like how your colors showed the curves of the hand in the green areas - showing (amongst other things) perhaps that image would be stronger if the background was a mid tone.

I'm getting better with blend-if, but seldom/never use the channels. Note to self - play with channels! Thank you for that link, I will check it out. (EDIT .. and apply image too - thanks Frank)
Ya'll have definitely left me far behind. I don't know what you did with which of the many sliders on "blend if" (upper, lower, left, right, split or not). And I don't know what is supposed to happen next, in either Piet's or Frank's examples, and how I'm to use it for what.

I took a regular picture and by adding three different tonality layers, can push some sliders and make some things turn black or white instead of the colors they are supposed to be. But I am clearly missing some key concepts here.

Channels are another enigma, and the luminosity masks that go with them.

I ended up with a hot mess. I could see some effect from the layers with the darks and brights but not from the midtones, except if I pushed the sliders far enough the whole picture would turn tan. Is it because I picked too complicated a picture? Or just because I don't have a clue?
We will get it... When I did mine, the darks were on the bottom, then the Mids, then the Lights on top. The slider you have to adjust is the underlying layer (the bottom one) - but you know that! You have to set the sliders to set matching ranges. Luckily there are numbers that document the Left Side (dark) and the Right Side (light). My values were:

Light Layer - 133-255 -- on top -- the light layer is applied to anything beneath that is between 133 and 255.
Mid Layer - 79-133 -- in middle -- the mid layer is applied to anything beneath that is between 79 and 133.
Dark Layer - 0-79 -- on bottom -- the dark layer is applied to anything beneath that is 0-79.

I think truly it would be better if it was 0-78 and then 79-whatever, etc.. You see what is happening. Yeah, I saw the go gray sometimes too, I haven't figured out why it does that.

You can see how those ranges would "carve up" the image into three distinct groupings. Of course you could always "soften" the edge by using Alt on the slider button, but then you would lose the crisp edge.

We aren't going to lose you on this one!! Once you see how those ranges work, you can add more another one and divy it into four groups for example. The secret is to have the ranges be distinct and mutually exclusive.

Edit - and when you replace a value-range, it is best to replace it with a color/tone that is in the SAME range, otherwise, things get messed up above.

LOL - Frank answered too!

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Post by minniev » Sat Jan 26, 2019 12:11 am

Psjunkie wrote:
Fri Jan 25, 2019 10:45 pm
my brain is slow this afternoon...here is the image completed for you to open in a new tab next to your original and be able to see the difference...
I'm not doing this right. Trying to copy what you did, this is what I get.
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Screen Shot 2019-01-25 at 6.09.45 PM.png
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Post by Psjunkie » Sat Jan 26, 2019 12:14 am

Try holding down the alt/option key and splitting the slider..move the right half of the slider all the way right then the left half to taste...

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