Newsgroups: comp.sys.next
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!mitroo
From: mitroo@magnus.acs.ohio-state.edu (Varun Mitroo)
Subject: Re: ColorStation questions
Message-ID: <1991Apr30.150026.9826@magnus.acs.ohio-state.edu>
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References: <1991Apr24.231003@ece.arizona.edu> <1991Apr25.180420.9712@menudo.uh.edu> <1991Apr25.221947@ece.arizona.edu>
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Date: Tue, 30 Apr 1991 15:00:26 GMT
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In article <1991Apr25.221947@ece.arizona.edu> dan@ece.arizona.edu (Dan Filiberti) writes:
>
>Alright, this is to all the smartass comments I've been getting.

	That's because your original post was faulty and ignorant.
>
>Almost all the news in this newsgroup that I've been reading
>claimed that the ColorStation has 4096 color "palette" and
>16 some odd million colors to choose (that's 8bits, rgb, for
>you illiterates who have responded to my previous posting).
>
>This implies that the palette can be modified.  My posting
>was in repsonse to the statement that there are 3 LUTs, rgb,
>each adressed by 4 bits and returning an 8bit value.  I 
>assumed that the 8bit value was modifiable.  Thus, you can
>choose 16 colors ( thats one per 4bit address, rgb), and
>the rest are permutations of those 16...ok, understand
>what I was saying now?  Sorry if my typo (six instead of
>sixteen) confused you that much.

	The palette cannot be modified by the user.  The look up
	tables are controlled by the computer depending upon the
	brightness level of the monitor to give the best range of
	colors.
>
>This allows for only 16 shades of grey, red, green or blue.
>
	This is 16 shades of pure red/green/blue.  Correct.

>Now, people are posting that the Colorstation has a
>static CLUT of 4096 colors... that means that 4bits
>rgb divide the 16.7 million colorspace into 4096
>colors.  Which means that the statement that the ColorStation
>has 16.7million colors to choose is a LIE.  There are
>only 4096 colors available, and unfortunately only
>16 shades of pure red, green, blue, or grey.  And, if this
>is true, then why do they even need CLUTs or palletes?
>It completely defeats there purpose.

	What are you saying?  Yes, the colorstation has "only"
	4096 colors.  You may want to study a little more about
	color on computers before you make comments like this.
	4 bits/pixel gives 16 shades of a pure color.  However,
	these 16 shades are not best represented by linear
	differences between them.  (ie intensity 8 is not twice
	as bright as intensity 4).  These colors must be adjusted
	to appear as distinct from each other as possible.  This
	is called gamma correction, I believe.
>
>As to why this is a problem, here it is.  Our research
>involves determining whether diagnosis of images by
>dermatologists is affected by things such as color
>quantization, image coding, compression, etc...
>Unfortunately, you can't determine this by showing
>dermatologists dithered pictures all of the time.
>You must show them "ideal" images, 24bit truecolor.
>So, the Next ColorStation is useless for this purpose,
>except for showing the dithered and quantized images.
>And, as you can see, with only 16 pure shades of
>red available, this may not work either, (since skin
>is predominately red).
>
	Does resolution have anything to do with this?  Do you
	have any idea what you're talking about?  Since when is
	skin predominantly red??  Could it possibly have
	a tinge of blue?  If it does, you have effectively
	doubled the number of colors from 16 to 32.  How about
	a greenish tinge?  Maybe you could have imparted this
	wisdom to Cezanne or Rembrant to always paint skin red
	rather than worrying about "warm" and "cool" colors.

	Before you make these idiotic claims, you might try
	any or all of the following:
	1.  Study a little bit about how the human visual
	    system works
	2.  Read a little bit about color theory
	3.  Read a computer graphics textbook concerning color
	    representation/dithering/anti-aliasing
	4.  Go to an art museum and look carefully at some
	    portraits - maybe even look at some paintings
	    by Seurat
	5.  Buy a copy of Frank Netter's Atlas of Human Anatomy
	    and look at some of his illustrations of skin
	6.  Actually look at a colorstation screen

>As for upgrading to the NeXTDimension board, that 
>would be fine, for 24bit color.  But, how you going to
>get the highest resolution images into the frame 
>grabber without RGB input?  S-Video and NTSC are 
>degraded signals, and once again, for our research
>you must start with the best.  There are many others
>who require RGB input also, especially since its the
>only way to get the highest quality image into the
>frame buffer from a camera.
>
	The one reasonable complaint you have.  The
	NextDimension should have RGB input.



-- 
You are young, they are old Control is all they've got to give
Just live how you want to live Tiny things that make you slave
Like a chain, an anchor to the bed of the sea
