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Author Topic: CS5 - How to select luminance range (spanning different colors)?  (Read 11256 times)
AFairley
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« on: September 26, 2010, 01:16:02 PM »
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I have not been able to find a way to select all parts of an image within a certain luminance range, no matter what the colors in that range are.  (What I want to be able to do is to select the luminance range, use the selection to create a mask so I can create an adustment layer to bring the values of everything in that range up or down together. Short of like a hyperfocues brightness adjustment, if you will.  Going into channels and usinge the autoselect there doesn't really help because I want to mask midrange values, plus I want an all or none mask anyway.)  Surely there is a way?

Thank you
« Last Edit: September 26, 2010, 01:22:31 PM by AFairley » Logged

Slobodan Blagojevic
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« Reply #1 on: September 26, 2010, 01:38:01 PM »
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How about Select>Color Range>Select: Highlights, Midtones, Shadows (in CS4 though)?
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Slobodan

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AFairley
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« Reply #2 on: September 26, 2010, 01:59:07 PM »
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How about Select>Color Range>Select: Highlights, Midtones, Shadows (in CS4 though)?

It's too locked down -- you can't vary the range it selects.  Ideally, I'd like to be able to click on a point with the eyedropper and expand the range with a slider, or use the + eydropper to expand.

One thing I just tried was to copy the collor image, convert to grayscale, select in the grayscale image by color range, expand as I wanted with the slider, create the adjustment layer mask, drag the adjustment layer onto the color image and align the mask on the image, but it seems a somewhat kludgy solution.
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Mark D Segal
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« Reply #3 on: September 26, 2010, 02:43:27 PM »
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If you are using adjustment layers for making the edits to the range you wish to select you can try using "Blend If" in the Layer Style dialog, adjusting those sliders to the range you need to include/exclude; it also allows the selection to be graduated so the transitions are not abrupt.
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Mark D Segal (formerly MarkDS)
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« Reply #4 on: September 26, 2010, 04:54:59 PM »
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Try this -
http://goodlight.us/writing/luminositymasks/luminositymasks-1.html
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AFairley
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« Reply #5 on: September 26, 2010, 05:17:46 PM »
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Wow!  That would do what I want, I guess.  I suspect a donation to get the actions is the most time/cost effective way to go.  Thanks.
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tived
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« Reply #6 on: October 05, 2010, 07:19:44 PM »
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i went ahead and donated/purshased the actions, though i haven't had time to use them.
i just wanted to say, that within hours i had the actions, a follow up email addressing my concerns regarding the large download via email.
All in all a very positive experience. I will get back to you all when I have had some time to play with the actions.

Good service

Henrik
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stephenmarsh
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« Reply #7 on: October 06, 2010, 02:18:45 AM »
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Wow!  That would do what I want, I guess.  I suspect a donation to get the actions is the most time/cost effective way to go.  Thanks.

The method mentioned by Mark in Post #3, Blend If Gray, is exactly what you were asking for, and it is free, just waiting there to be used in adjustment layers or standard pixel layers (in this context, "gray" equals RGB luminosity values).


Sincerely,

Stephen Marsh

http://binaryfx.customer.netspace.net.au/ (coming soon!)
http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/
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AFairley
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« Reply #8 on: October 06, 2010, 01:43:49 PM »
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The method mentioned by Mark in Post #3, Blend If Gray, is exactly what you were asking for, and it is free, just waiting there to be used in adjustment layers or standard pixel layers (in this context, "gray" equals RGB luminosity values).

True, though I think it would require me to sample luminance values and manually dial in the range I wanted, which would be OK.  I don't see how to graduate the transitions, though...

Thanks!
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stephenmarsh
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« Reply #9 on: October 06, 2010, 03:21:52 PM »
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True, though I think it would require me to sample luminance values and manually dial in the range I wanted, which would be OK.  I don't see how to graduate the transitions, though...

Thanks!

If one is after a precise range, then yes, one would need to sample* the start and end of the range of tones required (if eyeballing is not good enough for this context). *The info palette does not report luminosity values (RGB luminosity is not the same thing as Lab mode lightness).

One opt/alt clicks and drags the slider "triangle" to split it in two, in order to graduate the transitions.

More here:

http://members.ozemail.com.au/~binaryfx/blendif.html


Best,

Stephen Marsh

http://binaryfx.customer.netspace.net.au/ (coming soon!)
http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/

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Slobodan Blagojevic
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« Reply #10 on: October 06, 2010, 03:26:43 PM »
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... I don't see how to graduate the transitions, though...

By splitting the sliders...hold down the Alt key (Option on the Mac) and drag one-half of the slider away.
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Slobodan

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AFairley
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« Reply #11 on: October 06, 2010, 05:23:27 PM »
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Stephen, Slobodan, thank you for your help.
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Rob Reiter
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« Reply #12 on: October 07, 2010, 04:19:22 PM »
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On a Mac, in CS5:  Cmd-Opt-4. Then go into Quick Mask (Q key) and call up Levels (Cmd-L) and adjust the Input Level sliders to select the highlight range and mask density. Exit Quick Mask and you've got your selection.

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BradSmith
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« Reply #13 on: October 09, 2010, 03:08:37 PM »
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Rob,

What command are you giving it with "Cmd-Opt-4"?  I've tried to do what you said using CS3, but it didn't come out as your screen shows.
Brad


On a Mac, in CS5:  Cmd-Opt-4. Then go into Quick Mask (Q key) and call up Levels (Cmd-L) and adjust the Input Level sliders to select the highlight range and mask density. Exit Quick Mask and you've got your selection.


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stephenmarsh
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« Reply #14 on: October 09, 2010, 04:47:31 PM »
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The keycuts to load channels as selections were changed in CS5 (although one can get the old ones back). RGB luminosity can't be loaded from the composite~ (grayscale) or individual separate R, G or B (RGB brightness) channels. This may not be a concern for some editing methods, however for other methods it will make a huge difference and is a major concern - if one is after the true luminosity values of the  image (luminosity as defined by the Photoshop painting/layer blending mode).


Stephen Marsh

http://binaryfx.customer.netspace.net.au/ (coming soon!)
http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/
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Rob Reiter
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« Reply #15 on: October 09, 2010, 06:47:28 PM »
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Well, that's the problem. Adobe has changed this command several times. I believe at one time it was Cmd-Opt-Tilde (the upper case of the key to the left of the number "1".) Frankly, I don't want to think of the amount of time I've spent hitting all the control/shift/option/command keys in conjunction with the the the first four number keys...

But it will work in CS3 and it's a great help.
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stephenmarsh
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« Reply #16 on: October 10, 2010, 02:04:53 AM »
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Well, that's the problem. Adobe has changed this command several times. I believe at one time it was Cmd-Opt-Tilde (the upper case of the key to the left of the number "1".) Frankly, I don't want to think of the amount of time I've spent hitting all the control/shift/option/command keys in conjunction with the the the first four number keys...

But it will work in CS3 and it's a great help.


Agreed Rob, it is a real pain to relearn ingrained keycuts, this becomes a "balancing act" when different Creative Suite apps are being "integrated" vs. leaving a "stand alone" application alone so as not to confuse long term users. BTW, my mistake, it was in CS4 that things really changed:

http://blogs.adobe.com/jnack/2010/05/use_legacy_shortcuts_option_in_cs5.html

Back to my original point, the composite/master~ channel in the channels palette does not use RGB luminosity values, so one can't load RGB luminosity using a keyboard shortcut when the image is a standard full colour RGB. Even though there is a long standing tradition of people [mis]using the term "luminosity mask" when talking about loading the composite channel as a selection - the data is grayscale mode and not "luminosity*" (*RGB Luminosity as defined by the Photoshop layer blending mode or painting blend mode). Yes, grayscale mode has "tonal values" - however these are not the same values as found in the RGB luminosity values.

The OP was after a way to isolate a range of luminosity values. Only a small amount of Photoshop tools directly use RGB luminosity values. The composite channel as a selection does *not* use luminosity values, it will create the same values as your working grayscale space. The blend if gray option *does* use RGB luminosity values. As mentioned earlier, it may or may not actually matter in practice, it all depends on what one is trying to do.


Stephen Marsh

http://binaryfx.customer.netspace.net.au/ (coming soon!)
http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/
« Last Edit: October 10, 2010, 02:06:41 AM by stephenmarsh » Logged
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« Reply #17 on: October 10, 2010, 04:31:38 AM »
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Another way to create a selection of a very tight range of tones in your image is to use either the Threshold or Gradient Map adjustment layers. With the Threshold adjustment layer you define a luminosity value between 1-255, then create a stamped layer above this, copy this layer and you can paste it into a channel, anything below 125 and you'll need to invert the channel. This technique always benefits from a small amount of blur to smoothen out the pixel range.

Using a Gradient Map adjustment layer is a bit different, and also relies on the "Colour Range" selection tool which can be inefficient at the best of times, but combined with a hard coloured Gradient Map works quite well. Basically you create a Gradient Map layer then open the gradient editor and use a nice bright saturated blue for your blacks, then a nice bright saturated red for your whites, the create a third colour stop in the middle using either a white or a bright saturated green. Now you can move the position of your green colour stop to a specific tonal range in your original image, close down the blue and red to narrow the range of green. Now using Colour Range you sample greens only and adjust the fuziness to suit. This method gives you great control over what tones you want selected based on what pixels you make green using the Gradient Map. Attached is a quick example creating greens in a midtone and then using colour range to select the greens.

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Rob Reiter
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« Reply #18 on: October 10, 2010, 10:26:04 AM »
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I'll admit, then, to being confused on the issue, but the technique I describe does give me a way to select the highlights for masking, and that is how I heard it described-a "highlight" mask.  I guess I've never needed to distinguish between that and luminosity. Sorry to have confused the two.
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stephenmarsh
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« Reply #19 on: October 10, 2010, 03:22:59 PM »
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I'll admit, then, to being confused on the issue, but the technique I describe does give me a way to select the highlights for masking, and that is how I heard it described-a "highlight" mask.  I guess I've never needed to distinguish between that and luminosity. Sorry to have confused the two.

Rob, the context of this discussion from the OP is "I have not been able to find a way to select all parts of an image within a certain luminance range, no matter what the colors in that range are." - this is where my posts have been coming from. In this context, luminosity is a very specific beast (as defined by the Photoshop blending math).

The RGB luminosity data of an image will not change the appearance/values of the underlying RGB layers when set to luminosity blend mode (for example, paste the green channel as a layer over the RGB layers and set to luminosity blend mode, this is not luminosity).

It has become common "photoshopspeak" to mis-title the method of loading the composite/master channel as a selection as creating a "luminosity" selection, however this data is not the true "RGB luminosity" of the image (although the grayscale mode tones do have luminosity levels).


Sincerely,

Stephen Marsh

http://binaryfx.customer.netspace.net.au/ (coming soon!)
http://members.ozemail.com.au/~binaryfx/
http://prepression.blogspot.com/
« Last Edit: October 10, 2010, 03:27:58 PM by stephenmarsh » Logged
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