Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
...
> 
> Of course, perceptual rendering won't necessarily leave image L=50
luminance
> at L=50 reflectance but you can print an L step wedge to see where
each step
> gets mapped to - I think....someone who understands Perceptual
rendering a
> lot better than me can chime in here: is it image dependent or a
mapping of
> greyscale that can be measured by printing a Lab step wedge?

Not image dependent. Perceptual rendering is characterized by the
nature of the two spaces involved, regardless of image content.
For example, perceptual conversion from a large color to small color
space will shrink gamut based on the spaces, even if there are no
(destination) out of gamut colors in the file.
Hope that wording makes sense.

>  BTW is there a
> way to read the proof image values ie the pro forma image values for
a given
> proof?  My understanding is that there is not and that PS will only
display
> (Info palette) the image values.

One hack might be to load your eventual print space as your working
space but leave your file in it's original space when opening, but it
must be tagged. Then info palette should show the destination numbers,
just as CMYK does for rgb files. I'm assuming this will happen, but
not positive. Obviously rgb to cmyk is a color model difference as
well, and what you want is between two gray spaces.
A bit inconvenient, but if you were really curious at some point in
the workflow, you could check it out.

Tyler