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Grey Chanell (in Grey mode) selection problem?


SeniorS

SeniorS

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Hello!

I have another question about GREY images.

Example:
grey.jpg

CTRL+click on grey channel theoreticly (by my theory) make selection from white depending on its value. So cuting out must leave transparent greyscale image. But it don't (okey, it do, but changes black value):
grey_cut_selection.jpg

The same selection inverted and filled with 100%K gives correct result:
grey_invert_selection_filedjpg.jpg

Is my "theory" about CTRL+click selection wrong?
Becouse for my point of view, both ways should give same result.

P.S. I must be miss something.
 
I think problem is in CUTING. Becouse selection is okey (checked it and on 25% grey is 75% selection). Maybe something with antialiasing.
 
Problem - CTRL+click then CUT then flatern (or on white background) and image (theoreticly) should be the some as original.
 
not sure what you are saying your percentages don't add up?
 
Something like that.

First image is original. Then i press CTRL+mouse click on grey channel in Channels panel. That creates white value selection. Now i CUT it and expect that now i have transparent image with black values exact as original. But when i flatern it or put on white background (or by eye drop) i notice that only value which is correct is 100%K all others changed (showed in second image).
Third image shows that selection itself got no problem. Because the same selection inverted and filled with black gives correct result.

So, after thinking (and 2 cigaretes) i assume that cutting works not the way i understand.
 
Sorry still confused, none of those images look transparent to me... I must need more caffeine lol
 
Wake up, iDad, wake up....

I think understand, I hope.

When you make your selection, PS will select whatever shade of white in the the last 3 swatches (75, 50, 25). Why the 100% swatch wasn't affected? Coz basically there's no shade of white.

So naturally, when you cut / delete the color values within the selection, you altered the black values of the last three.

When you inverted the selection, you are selecting the true value all 4 swatches. You may have filled it with 100%k but the 3 last swatches was filled with it's particular shade of black.

As an experiment.... after selecting the black of the original image..... on a new layer..... fill with white..... it will show you the white opposite of the first image.


iDad.... got an aspirin?.... lol
 
Last edited:
No but I'll send over a coffee...LOL
 
LoL...and...LoL...and LoL...and...:eek: :eek: :eek: and OH MY GOD!!!

dv8_fx after your post i get it. I assumed that, that CTRL+ select WHITE pixels!!!
I lived with that illusion for YEARS!!! I don't remember how i get that illusion that was so long ago.
I understand that it a selection but using it that way my head told me that it selected pixels color specific values (not whole pixel with transparency)!

Luckily i didn't have to make transparent greyscale images (ussualy they on white and stays on white or are dark and "strong" so not noticable mistake)

I used sometimes with CMYK images but with different needs and it did the tricks.


I just got mental kick in the head! Revelation!

My brain hurts, i need aspirin too :bustagut::bustagut::bustagut:



P.S. Intresting how many such illusions i got from learning stuff from practical education but not much draw attention to theoretical side.
 
I must add..... that's my interpretation of the problem.

I've also noticed that myself but never did give much thought to it.

I just figure that 75% black has to have 25% white.
 
Yes, thats it. Mathematic said so :)
Where was 25%K cutted with 75% selection. 25-(75% of 25)=25-18,75=6%K
---------- 50%K ----------- 50% --------. 50-(50% of 50)=50-25=25%K

So it how it should be. I was looking on Quickmask and see these percentage but mind tricked me.
 
SeniorS said:
Yes, thats it. Mathematic said so :)
Where was 25%K cutted with 75% selection. 25-(75% of 25)=25-18,75=6%K
---------- 50%K ----------- 50% --------. 50-(50% of 50)=50-25=25%K

So it how it should be. I was looking on Quickmask and see these percentage but mind tricked me.
Click to expand...

At least you know the math of your colors.... I don't... :cry:

:thumbsup:
 
Yeah...but it don't do any good if algoritm is absolutly wrong :D


P.S. actually one of reasons i added math is that not to feel like total idiot! :bustagut:
 
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