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work in rgb save lab or cymk mask,how can i do it?

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  #1  
Old 12-28-2011, 01:57 AM
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mantra mantra is offline
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Wink work in rgb save lab or cymk mask,how can i do it?

Hi

i work in rgb
can i save in my photo rgb lab or cmyk masks ?
i mean in lab mode there are 3 channels ,luminosity and A/B with colors
in cmyk i like the black channel

my goal is
1) have a mask luminosity created using the lab mode

2)a second mask with all the colors created using the lab mode

3)and a third mask with the blacks created using the cymk mode

well
i loaded my photo in photoshop i'm in RGB mode
now
image->duplicate
on the second image(copy) i set lab , now i have 3 channels
luminosity and a + b

i want to get the masks of all the luminosity and all the color in lab mode , save these 2 masks in my rgb photo

please let's focus on colors
i have 2 channels ,a and b

how can i do ?
click ctrl+shit on A and after B ->select ->save -> document the photo in rgb

or select A, select all , copy and paste , do the same with b ...and so on

and how about the black in cymk ?


the point , sorry for my poor english, is that i want take benefit of lab and CYMK, for example have a mask of only the black and use in rgb mode

thanks
cheers
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  #2  
Old 12-28-2011, 02:31 AM
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amica999 amica999 is offline
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Re: work in rgb save lab or cymk mask,how can i do

Once you have copied your doc (not the layer!) and changed the mode to LAB, you ctrl-click on the lightness channel to have the luminosity selected, save that selection: Select-> save selection as a new channel. Back in your RGB go to selection, load selection; select your LAB copy in the document drop down and select the newly created channel in the channel drop down -> voila :-) Same goes with a + b channels which yoiu have to save first and of course BOTH docs must be opened!
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  #3  
Old 12-28-2011, 03:10 AM
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John Wheeler John Wheeler is offline
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Re: work in rgb save lab or cymk mask,how can i do

Hi Mantra

Amica has a good approach. There is another way where you do not have to duplicate each channel into a new channel where you can move the masks/channels of Lab or CMYK duplicate images into new masks/channels in your RGB document.

There are many ways to do so yet the most flexible is using the Image > Calculations Command. It actually is so flexible and powerful there is a little learning involved. Here is the link to the Adobe help file on that command: http://help.adobe.com/en_US/photoshop/cs/using/WSCB346BE1-FE43-4cbb-8606-B26EFF1298A9a.html

It allows you to pick any open document, any layer (or merged layers) and then any channel (color or alpha). In addition, if desired you can combine that selection with a totally different channel from another (or the same) document. This may be useful for combining the a and b channels together.

Sometimes the simpler more straightforward approach (e.g. Amica's) is best even if there is less capability/flexibility. Just pick the approach/path that works for you.

The main unanswered question for me is how you want to combine the Lab "a" and "b" channels. Each is effectively its own grayscale image. You just have to decide how you want to combine them. This would be not different than considering how to combine any of the two of the three RGB channels. The Calculations Command has all the blending options available between two channels and most likely one of those would meet your need.

I think I would have to understand how you plan to use that combined channel in your RGB document. This may take a little more work because the a and b channel represent "no" color when the channle is at 50% gray. So using the a or b channel separately or in combination in an RGB document may not do what you wish. If you are just experimenting, then just go for it. If you have a specific need you are trying to meet in a mask, then if you describe that need, a way to get there can probably be figured out. Hope this or Amica's info is a helpful starting point.
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  #4  
Old 12-28-2011, 05:02 AM
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mantra mantra is offline
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Question Re: work in rgb save lab or cymk mask,how can i do

Quote:
Originally Posted by amica999 View Post
Once you have copied your doc (not the layer!) and changed the mode to LAB, you ctrl-click on the lightness channel to have the luminosity selected, save that selection: Select-> save selection as a new channel. Back in your RGB go to selection, load selection; select your LAB copy in the document drop down and select the newly created channel in the channel drop down -> voila :-) Same goes with a + b channels which yoiu have to save first and of course BOTH docs must be opened!
thanks Amica999
but your tip will not give me only the lights , and not all the luminosity (shadow +midtones+ lights)
thanks
cheers

ps amica999 beautiful photostream in flickr
did you release some tutorial?
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  #5  
Old 12-28-2011, 05:19 AM
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mantra mantra is offline
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Question Re: work in rgb save lab or cymk mask,how can i do

Quote:
Originally Posted by John Wheeler View Post
Hi Mantra



There are many ways to do so yet the most flexible is using the Image > Calculations Command.

thanks John Weeler
i read careful the adobe link
but i did not understand well
might you tell me how use the powerfull calculation feature to obtain a mask created on the black channel in CMYK
I mean the steps


Quote:
The main unanswered question for me is how you want to combine the Lab "a" and "b" channels. Each is effectively its own grayscale image. You just have to decide how you want to combine them. This would be not different than considering how to combine any of the two of the three RGB channels
.

in the lab mode ,photoshop seperates the luminosity from the colors
the colors are inside the a and b channels
so i would like to have a mask with all the colors that i can find in a and b
i got it the point
maybe there is a way to obtain them
thanks
sorry for my poor english
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  #6  
Old 12-28-2011, 08:42 AM
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amica999 amica999 is offline
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Re: work in rgb save lab or cymk mask,how can i do

Quote:
Originally Posted by mantra View Post
thanks Amica999
but your tip will not give me only the lights , and not all the luminosity (shadow +midtones+ lights)
thanks
cheers

ps amica999 beautiful photostream in flickr
did you release some tutorial?
Tante grazie, Mantra, I'm still learning like you, so no, I'm not in the position to release tutorials :-)

If you are looking for refining your luminosity masks, have a look here: http://www.retouchpro.com/forums/blo...ity-masks.html I've written an action, which will place the masks in your channel palette... Besides you can refine your masks painting with black and white/use levels/ use dodge and burn tools/ or normal brushes in overlay mode..it all helps. Have a great day, and if we don't hear prior: Happy New Year to you and your loved ones.
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  #7  
Old 12-28-2011, 10:22 AM
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mantra mantra is offline
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Thumbs up Re: work in rgb save lab or cymk mask,how can i do

Quote:
Originally Posted by amica999 View Post
Tante grazie, Mantra, I'm still learning like you, so no, I'm not in the position to release tutorials :-)

If you are looking for refining your luminosity masks, have a look here: http://www.retouchpro.com/forums/blo...ity-masks.html I've written an action, which will place the masks in your channel palette... Besides you can refine your masks painting with black and white/use levels/ use dodge and burn tools/ or normal brushes in overlay mode..it all helps. Have a great day, and if we don't hear prior: Happy New Year to you and your loved ones.
Vielen Dank für Ihre Freundlichkeit and Happy new year to you too
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  #8  
Old 12-28-2011, 05:30 PM
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John Wheeler John Wheeler is offline
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Re: work in rgb save lab or cymk mask,how can i do

Quote:
Originally Posted by mantra View Post
might you tell me how use the powerfull calculation feature to obtain a mask created on the black channel in CMYK
I mean the steps
Hi Mantra
Here are the steps by steps to take the Black Channel from a CMYK image and move that over as a Channel in the RGB Image. I will use my Avatar as an example.

- Create RGB Avatar Image and name it "Johns Avatar RGB":
Johns-Avatar-RGB-Composite.jpg

- Duplicate that image convert to CMYK and name if "Johns Avatar CMYK" The image below shows just the Black Channel being active:
Johns-Avatar-CMYK-Black-Channel.jpg

- Make the Johns Avatar RGB image active
- Set Image > Calculations as shown
Note: As long as Blend is set to Normal, Opacity is set to 100%, and Mask is not checked, only the values in Source 1 matter and the values in Source 2 have not effect:
Calculations-Conversion.jpg

- Accepting the above calculations places the CMYK Black Channel into the RGB document:
Johns-Avatar-RGB-with-CMYK-Black-Channel-Move-Over.jpg

One thing to pay attention to is that the CMYK Black Channel shows dark where there is supposed to be Black ink. You may need to Invert this mask to have the function you want. This could either be done manually now or even more easily if you just click the Invert checkbox in the Calculations panel during that operation.

Quote:
Originally Posted by mantra View Post
in the lab mode ,photoshop seperates the luminosity from the colors
the colors are inside the a and b channels
so i would like to have a mask with all the colors that i can find in a and b
i got it the point
maybe there is a way to obtain them
thanks
I am sure I could help with creating a color mask yet I think there may be a language barrier. I thought of a way to break down that barrier using an image. The following image on the left side is just the pure hue of green in all combinations of luminosity from dark on the bottom to light at the top. Then from the middle going towards the left that is all combinations of desaturating the green. My question to you is what do you want masked on this image when you talk about Color, and which areas do you want masked when you want Shadow, Midtones, and Lights? If you could take this image, draw a boundary in this image for each type of mask you desire, I bet I (or other forum members) could provide the answer to your search (I remember you posted about this several months ago). As an example, if you define a color mask as those areas that have more of a tint of green whether light, dark, or midtone, that is simple a saturation mask as shown on the right side of the image (where saturation is defined by the Saturation Blend function). This mask is pretty easy to generate even just staying in RGB. If you are interested in pursuing this path, let me know and please provide the info as requested above. Hope this helps

Screen shot 2011-12-28 at 4.24.37 PM.png
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  #9  
Old 12-28-2011, 06:40 PM
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amica999 amica999 is offline
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Re: work in rgb save lab or cymk mask,how can i do

I came across Kristof's link for extended contrast on calculations base: http://www.youtube.com/watch?v=gUwlCMDr5m8

I have tried and added a curve to lighten shadows, but I don't see much advantage over using S/H adjustments for this purpose, on the other hand, I guess color manip would be a application...
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