Bit of a Con Really - Follow-up ...

You can during processing.

--

*All those who believe in psychokinesis, raise my hand *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW To e-mail, change noise into sound.

Which process is an entire art & science of its own. It is *not* easy to do a good job of converting an RGB light image into CMYK pigments.

--
    W
  . | ,. w ,   "Some people are alive only because
   \|/  \|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

Um, this sounds a little confused. The important distinction is between

*additive* colour (eg; RGB) vs *subtractive* colour (eg; CMYK). With RGB, you're *filtering* a full spectrum illuminant, with CMYK, you're *absorbing* part of a full spectrum illuminant.

--
    W
  . | ,. w ,   "Some people are alive only because
   \|/  \|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

Ayup. When I was a kid, our first colour set was a 27" Baird, which had a huge, hinged PCB with a kazillion pots on it, & an acetate overlay covering the whole thing, with diagrams printed on it to show what each pot adjusted. *Lots* of fun!

--
    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

Of course.

Those of us who take colour reproduction seriously use colourimeters to calibrate the screen & display card LUTs.

--
    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

People have been known to do it with Ektachrome type film (Ektachrome, Fijuchrome, AgfaChrome, Ilfochrome, etc) with varying success by tweaking the exposure and development.

At one time you could get Kodachrome developed to spec, which was intended to correct for mistakes in exposure, but it certainly would change color response.

In the printing process, either to film (used in movies) or paper, you could do all sorts of things.

Standard C-41 color film has an exposure latitude of less than one stop underexposure, but 4-5 stops of overexposure. As the exposure increases, color response, contrast and graniness change. If you like fine grained over saturated colors, try shooting a roll of ISO 100 color negative film and have it processed normally.

Technicolor which is actually a black and white negative process (producing seperate red, green and blue negatives on black and white film) could very easily be manipulated and often was. Look at the recent prints (or the DVD from them) of The Wizard of Oz.

The original intention was to produce a movie that was almost cartoon like in its color, later prints were much more subdued, almost "normal" in color as well as the video tapes made from them.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM

I agree with what you're saying, it just wasnt the point I was addressing.

NT

You can actually.

Why do color enlargers come equipped with color filters then?

Correct.

This bothers me. It might be true in a practical sense, but it's always struck me as being theoretically wrong (mostly because of the extreme overlap of the eye's blue and green receptors). I won't start an argument, though, because, even if my intuition is correct, I don't have the "science" to back it up.

How? The film's color response is basically set by the choice of sensitizers.

You can adjust the balance, but that's not the same thing.

It does. One specifies that with colour temperature. Eg; direct sunlight is about 5000K, while shade is up around 6500K, & tungsten light bulbs are down around 2400K. Higher temperatures are biased towards blue, lower are biased towards red. The white balance of a screen or an image is specified in the same way.

There is: 6500K, which is what I have my monitors calibrated to. Traditionally, the print (CMYK) media use 5500K.

In general, that's true, although it's common for LCD monitors to have a factory WB of as much as 8000K, as it makes the image zappier.

--
    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

Its only confusing to people that don't understand that backlit LCDs, like CRTs, add three primary colours together to make a colour image. The source (phosphors or white light tubes/LEDs with colour filters) of the primary colours may vary but the process is the same.

It is not the same as a slide which filters each pixel (that's picture element to the one who claimed slides don't have pixels) through several coloured layers or prints that do it with inks of various shades.

Colour transparencies aren't printed images.

--
    W
  . | ,. w ,   "Some people are alive only because
   \|/  \|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

You're completely missing the point. Once again, projected colour transparencies are nothing like printed images.

--
    W
  . | ,. w ,   "Some people are alive only because
   \|/  \|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

Yeah, okay, you can, but it's rarely done.

-- W . | ,. w , "Some people are alive only because \|/ \|/ it is illegal to kill them." Perna condita delenda est

---^----^---------------------------------------------------------------

That's true, but it's a joke compared to being able to directly tune the black level & amptitude of RGB levels on an LCD panel or CRT.

--
    W
  . | ,. w ,   "Some people are alive only because
   \|/  \|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

Nothing like to the degree that you can with CRTs or LCDs.

--
    W
  . | ,. w ,   "Some people are alive only because
   \|/  \|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

One of 5500-6500K, typically.

--
    W
  . | ,. w ,   "Some people are alive only because
   \\|/  \\|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------