Help with GIMP channel problem needed.

[Midgardsormr]

Glad it's useful! I haven't been doing much in the way of mapping lately, but I do love helping people out, and these sorts of questions are just my cup of tea.

[johnvanvliet]

back in 99 / 2000 when i moved from the photographic darkroom to the computer
-- 15 years makes a HUGE!!!!!! difference --

using the physical "imagery" helps

the "channels" are in the additive RGB mostly and not in the subtractive that i used to "think in" CMY
so a "channel" is the RGB emulsion layers ON THE FILM ( yes there are 6 layers 3 fast and 3 slow on film )

a layer and mask are basically the same - they just do different things
a mask is well a MASK it blocks things

a layer adds or subtracts or mixs things
pop in two 4x5 cm negatives into the enlarger and you have " 2 layers "
pop in one negative and a MASK - still have 2 layers BUT part of the paper on the easel will NOT be exposed
for that you pop in the second negative and the negative mask you made and expose THAT part of the paper


the VERY nice thing about using a computer to do this is ALIGNING them and the many many many layers one can add

and all the FUN things that can be done

-- just try to remove a person from wedding photos
-- easy NOW but back in the 70's and 80's ?????????????

[Midgardsormr]

For those who move from additive to subtractive color spaces or vice versa, it's helpful to know that the additive primaries (RGB) are complementary to the subtractive primaries (CMY), and in that same order. So if you find yourself thinking "This needs more yellow," that's the same as "This needs less blue."

[johnvanvliet]

i still after a number of years still find my self wanting to use magenta and yellow to change colors in the gimp
-- it dose work, so no problems there

also thinking of "layers" as glass slides stacked one on top of the other can help

i do not miss the days of hand painting the kodalith film in the slide holder to make color presentations