Digital BW, The Print

Whoops.  Sorry, I have got this wrong!! In a linearization, it is log10(norm
pixel value) versus log10(luminance) or -Density that should be linear. (Not
0 to 1 on the x-axis as I did below!) Gamma 1.8, 2.2, nor LAB  are linear
when normalised pixel values are plotted against density.

Now I am really intrigued as to how a programme like QTR or IJC/OPM does
this given the log10(0) is -infinity.

What do you guys linearize?

(Boy, the below really was a piece of garbage thinking!)



> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Mon, 06 Dec 2004 23:33:36 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Just one more thought for the evening.  If QTR or IJC/OPM linearizes LAB
> values from (0, 0.04) to (1, 1.68) for EEM, as an example, then I believe
> this function is defined as y = -0.04 + 1.64x where x=log10(normalised pixel
> value) = -Density. If I am not mistaken this is a gamma of 1.64.  This also
> means 50% grey is printed with a density of 0.5337.  This is much lighter
> than what we want.  A 60% step (norm. pixel value 0.4) prints at 0.6926.  So
> a step from 50% to 60% was a change in density of 0.16.  Yet LAB would
> prescribe a change of 0.73-0.55=0.18.  So if I wanted to print a simple
> picture of 2 squares, one 50% grey and the other 60% grey this curve would
> not print them properly, even though they are well within the tonal range of
> the printer.
>