Message
Re: [colorvision_group] Backlight Film?
2006-03-13 by CDTobie@aol.com
In a message dated 3/10/06 5:00:01 PM, ttrostel@... writes:
Not that I really expect this to work but ...
I saw an article about an artist who liked to print nature pictures on
backlight films to hang in windows sort of like stained glass.
Now I know that the 1005 isn't designed to deal with transmitted light
measurements but was wondering if anyone tried setting it on a white
sheet of paper and trying a profile. I'm certain it would require a
bit of tweaking but might be interesting.
I've worked with backlit film quite a bit over the years and find that it is not necessary to profile it as a transparency (its not really a transparancey anyway, more of an translucency). First: the biggest variable is gamma, and that will vary with the lightbox used (and will vary constantly for window illuminated backlight film), so profling the film alone won't really cover that; since it does not capture the factor of the backlight.
Beyond that, I find that its actually easier to profile backlit film as a reflective media; by either placing it on a bright white background, profiling as reflective, and then editing the brightness as needed to adjust, of to start with a typical gloss relective profile, and edit that as needed. In either case, DoctorPRO is the favorite tool for such editing work, though you might manage to get away with using the brightness, contrast, and saturation sliders in PrintFIX PRO for the job, especially if you limit the ink used significantly before printing the target. You could even open the target (from the Targets folder in PrintFIX PRO) in Photoshop, move the center levels slider to lighten the target, and print it that way, even if you aren't going to use a similar gamma lightening curve with the final prints. Remember we are emulating what will be seen backlit, from what the spectro is reading front lit, so such a trick has a certain logic.
Sounds like you had already thought of most of this. Another item: Dyes are a more normal backlit medium; pigments don't glow like stained glass windows, though the newer encapsulated micropigments come a lot closer (the light still can't go through, but it goes around a lot better). And a pigment backlit film will last longer than dye, which can fade and color cast in an amazingly short timeframe. But pigments, by being less transparent, may require more lightening to be effective, and that lightening may weaken saturation. And of course this brings us to the issue of adhesion to backlit films; gloss black is needed, and overspray is a good idea too...
C. David Tobie
Product Technology Manager
ColorVision Business Unit
Datacolor Inc.
CDTobie@...
www.colorvision.com