Digital BW, The Print

Forget that - it's completely flawed.  A linear Lab model from perfect black
to perfect standard illuminant white suitably models our vision process.

Generating a linear Lab profile is a compressed environment is easy.  We do
that when we linearise the printer.  But we know this results in flat,
lifeless prints.  Colour guys go on to do scale for the imperfect black and
white points and something's gotta give.


> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 20 Oct 2005 01:09:09 +0100
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Conversation: [Digital BW] ICC v. Transfer Function in Epson driver
> Subject: Re: [Digital BW] ICC v. Transfer Function in Epson driver
> 
> 
> I have not read the last few posts on this subject but I thought I'd throw
> this out for thought - I myself am still thinking about it (still awke at
> 1am) and I wish I could consult someone that new the answer!
> 
> Sketch the following.  Light intensity on the x axis from 0 to the "standard
> illuminant" D50 lighting.  First plot "perceived brightness". As we know
> human vision is not linear and you get sharp increases in perceived
> brightness at the beginning, flattening ever more off as we approach full
> brightness of our illuminant (same applies to all human sensory experience:
> sweetness, bitterness, audible volume etc).  From everything I have read
> XYZ_Y is about the best model of human "perceived brightness" we have.  So
> this plot is best approximated by XYZ_Y and is 100 (or 1 depending on
> notation) at the standard illuminant.
> 
> Now plot L*.  L* is a linear concept.  As we move from no light to full
> light L* moves evenly from 0 to 100.  When we get to 100% of the standard
> illuminant, L* is 100.  Does this make sense so far?  I think it does.
> 
> Now compare the two lines.  At the low end of the scale very small increases
> in L* are associated with large increases in perceived brightness (loosely
> labelled luminance).
> 
> Maybe I am talking through a hole in my head here but does this answer our
> issue about small gradations in  L* at the dark end of a visually pleasing
> greyscale?
>