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Trouble following the luminosity mask tutorial.
#3
That looks like the same tutorial. But I was following the one from the gimp homepage here: https://www.gimp.org/tutorials/Luminosity_Masks/

Let me go through that and see if it answers my question. I'm not interested in a script as I'm trying to learn how to use it. I'll see if your explanation and pictures help, or I'll ask a more detailed question.

Thanks for your response.

-Kirby

So that's the identical tutorial, at least up to the point I'm failing. I'm going to give as detailed a walk through as I can to see if someone can spot my misunderstanding. I have dragged the red channel down and named it 'L'. At this point:

I select the image, (in image frame rmb -> select -> all) get the marching ants.

On 'L' channel I subtract the image (on 'L' rmb -> subtract from selection) Can now see the marching ants and diagonal bars marching.

Save as a new channel and rename (in image frame rmb -> select -> save to channel) which creates a new channel that I can rename 'D'. Still see the marching ants and diagonal bars.

Up to this point I feel like I'm good. Now let me create the DD channel:

To make sure I'm starting from the same point, I cancel the selection (rmb -> select -> none) no marching ants.

With the 'L' channel selected (note that none of these have the white boarder indicating that the selection is active like on the 'Layers' frame.) I select the image, (in image frame rmb -> select -> all) get the marching ants.

On 'D' channel I subtract the image (on 'D' rmb -> subtract from selection) Can now see the marching ants and diagonal bars marching.

Save as a new channel and rename (in image frame rmb -> select -> save to channel) which creates a new channel that I rename 'DD'. Still see the marching ants and diagonal bars.

I cancel the selection (rmb -> select -> none) no marching ants.

But now I look and the 'DD' Channel looks almost like the 'L' channel, not darker then the 'D' Channel.

https://i.imgur.com/81XA1Rh.png

If I repeat the process only subtracting from the 'DD' channel, to get a 'DDD' Channel, it looks dark, but about the same as the 'D' channel.

https://i.imgur.com/djxbAoP.png

Thanks for your help.

-Kirby
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RE: Trouble following the luminosity mask tutorial. - by kirbywan - 04-15-2018, 03:35 PM

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