QTR-Quadtone RIP

Hello again Franco.
I see what you are getting at in your question but I'm not sure that
many of us approach things in quite that way. We all want the maximum
darkest tone we can achieve for black in our prints irrespective of
what the viewing conditions will be. From that point on it becomes
necessary to actually alter the tonal relationships to suit any given
viewing environment if one is trying to maintain a specific "look" for
an image over the range of conditions you describe. I don't believe
that it is possible to overcome the physical realities that prevent
making a sort of universal print for all viewing levels.

In regard to the monitor image, it's my understanding that it is, and
should be, calibrated to a specific environment itself and it's view
won't be valid outside of that criteria either.

A gentleman, C D Tobie, who posts on this and the black and white
print group fairly often, most probably could address your question
with a much more technical explanation than I.

Regards
Duane
 



--- In QuadtoneRIP@yahoogroups.com, Franco Laeri <franco.laeri@...> wrote:
>
> Dear Duane,
> 
> thank you for passing your advice that I appreciate very much!
> Well, the taper from L* 17.6 to 5.5 refers to black levels between 45% 
> and 75 %... Let me contemplate the dilemma from an other perspective:
> 
> When printing an image I am primarely interested to obtain a print that 
> corresponds to the monitor image as close as possible. As the nature of 
> the monitor image (self-luminous) is different from the paper print 
> (reflecting ambient light) and the response of the human visual system 
> is different for various light levels, one has to carefully consider
the 
> conditions under which the comparison should be performed. Condition 1: 
> Matching the color temperature; condition 2: Matching the light
levels - 
> I try to match the light levels that pure white produces on the retina. 
> Given similar color temperatures - they can be approximately evaluated 
> with a spectrophotometer -  usual values for a monitor are around 120 
> cd/m^2. That is not particularly bright as anyone who has tried to work 
> with the laptop in the garden experienced... So, for a meaningful 
> comparison the print should be inspected at a correspondigly low light 
> level. The problem then is that at this light level the range of black 
> levels that the human eye is able to discern is limited. Depending of 
> the level of eye-internal scattering (-> age of the person) depper 
> blacks than d'log around 2 are hardly resolved. As a consequence I tend 
> to regard a grey level distribution in the print as ideal that matches 
> the one I observe at the monitor. I obtained this with Curve Creator 
> settings <ink level> 45% and <Black Boost> zero and corresponding 
> linearization: QuadTone RIP does a perfect job! However, when such 
> prints are inspected at higher light levels - in an extreme case in 
> bright sunlight - one recognizes the lack of depth in the deep blacks. 
> Although the middle gray distribution is still acceptable, I then would 
> like to see deeper blacks. It is for this case that I hoped that
setting 
> <Black Boost> would help.
> However, initiating the linearization with <Blach Boost> at 75% shifts 
> the middle grays to dark values. Values that might be acceptable under 
> bright light illumination, but when inspected at 120 cd/m^2 do not 
> correspond to the gray level distribution shown by the monitor. So my 
> question is, did you or somebody found a way out of this dilemma.
> 
> Many thanks for comments; regards
> Franco
> 
>