Is Graded Paper a Bit Multigrade?
I've been using Ilford MGIV FB (and previous variants) for a long time. Today I decided to try a few of my prints on a slightly expired pack of Galerie, grade 3. As I use an Ilford 500H dichroic head I did a test to see if I would get longer exposure times using just the "soft" green or the "hard" blue setting.
To my surprise the green exposure produced a very muddy soft print with no deep blacks and no clear highlights. The blue exposure produced very deep blacks and nice highlights (as I expected) from this grade. In effect, it seems to me, like the graded Galerie emulsion responded in a somewhat multigrade fashion.
Since I have never tried this comparison before I am wondering if it is common or a result of a mistake on my part, environment, or perhaps some longevity issues of the paper. If it is a common response of Galerie, I wonder if this is a potentially useful control.
I'd be happy to scan a couple of test strips if needed.
I think MG paper has many emulsions sensitive to green or blue, but graded paper lacks the multiple emulsions. I think graded paper is sensitive to blue.
I've had a similar experience and I've often wondered that myself. I'm interested to see what responses you get from this thread.
Thats kind of how the whole principle of multigrade paper was discovered.
Films and papers from the major manufacturers are made up of blended emulsions, and spectral sensitivities do vary. So it's not a big shock that it can happen in practice
Originally Posted by Rafal Lukawiecki
Wow that's cool. Rafal conducted a science experiment. I hope he keeps up the curiousity
Originally Posted by Ian Grant
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To have this happen, the contrast of the emulsion must vary with wavelength of the light used for exposure. The way to test this out is to repeat the experiment but using a step wedge for subject matter and then plot out the H&D curves to see what they look like.
This has a secondary value of being able to relate contrast grade to the exact color of light used for exposure.
Yeah -- the current Oriental is a 2-emulsion paper masquerading as fixed grade. It is made of two high contrast emulsions with slightly different sensitivities. Changing the filtration doesn't change the contrast, though. I think one of the east-bloc papers was also a 2 emulsion 'fixed VC' paper, but I can't remember which one it was.
I didn't know that Ilford was using color-sensitized emulsions, in different proportions for each grade, for its graded paper. That's really insipid.
Finding crypto-VC papers is rather easy (well, easy for some). If you take the derivative of the HD curve and end up with
then you have one. The 'teat' in the middle is where the two emulsions overlap. It is also possible to get a dip in the middle.
you can try dialling in some cyan on VC paper and you'll find the contrast changes contrary to what you often read. People forget these things called filters are actually filters and can filter out the wavelengths that the paper responds to in varying amounts depending on the cut off of the filter wave lengths and also the cut off of the paper spectral sensitivity.
I have an Aristo VCL4500 which is a two-tube variable contrast cold light head. The two tubes are blue-violet and green. In the instructions, it says about graded papers:
"Graded papers primarily like the blue energy spectrum. You can now select maximum blue, blue with adjustable intensity or blue and green combined. In the blue adjustable position you can set the intensity level to control printing speeds or adjust for dry down time. You can also print with blue and green combined and may find it possible on some papers to achieve plus or minus a half grade by adjusting the blue green ratio"
I have wondered about this. I haven't tried it. I will soon.
That was my impression: you could get fairly smooth control over a -1 grade by using the green light component with Ilford Galerie Graded 3 as compared to a blue exposure judging by eye only. I wonder if as long my results are consistently repeatable this might be a more convenient way to fine-tune contrast with graded papers than by using softer working developers, water baths, etc. I will be getting a fresh box of Galerie G3 to retry my tests.
Thanks everyone for your comments and encouragement.
Last edited by Rafal Lukawiecki; 08-11-2010 at 11:06 AM. Click to view previous post history.
Reason: PS. See next post for the scans.