RE: OT:colors [was:Re: layers]
This is how the plates are made for four colour printing. The process used for most books and magazines, catalogues etc (there are some that have even more plates, but its not four colour)
Yellow, cyan (a type of blue-green) ans magenta (redish purple) as wll as black are the plates. The plates (are) were made by photographing (actually now a computer program is used)the picture with these filters and a plate made. Each plate picks up coresponding colour and prints it onto paper. The plates have to be aligned. Occasionally you see a print, specially cheap flyers) where they are not aligned and one colour is offset. the four colours add up and voila, a colour picture.
The paper process has limits and there a number of out of range colours. Computer moniter is better but there are still some out of range colours.
Neil summarized the colour perception process in humans very nicely. If you want a demonstration of the opposing receptor pairing in the human eye, stare at a coloured spot (brightly lit) then close you eyes. There will be an afterimage in the reverse colour ( according to how the eye perceives it).
" I had to throw this in, because I find it interesting, it is fun, but not
directly related to Iris (unless you photograph them in black and white).
It is somewhat related to the color topic that has been developing. It
goes into the category of trivia.
I don't remember many details, but this is another peculiarity of color
First you photograph an image onto black and white film; you replicate the
photograph more than once using different colored filters for each image (I
forget which colors work best). These images will all appear black and
white, and will look pretty similar (maybe slight differences in relative
lightness and darkness of certain parts of the image). You can project the
images made with different filters together, or overlay them, and you will
see a colored image. I don't think I've ever heard an explanation of this,
but I'm sure wavelengths of light and our perception of them come into
play. I believe this is an old trick that was discovered before color
photographic films (papers) were developed.
I have not verified this, doubt it's true, but I've also heard that if you
do the same, but photograph a black and white image, it will bring the
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