What's interesting is that I had the same question, once upon a time.
Kodak puts out a table in one of their brochures that breaks it all down, and actually answers Kostas' question. But, my question before going into my packed library [recommend research here if . . .] to what purpose?
You can achieve any gradation with two filters. A Greeen and a Bluye (I forget the Wratton numbers), which is actually how those Multigrade enlarger heads work. Using the Blue, do a step test, that gives you the time for the dark areas, then with the green the step test gives you the time for the highlights. Make the two exposures with each filter. That's the economy of it. If there's another reason, maybe I can shed some light (pun intended) on the problem.
By the same token, if it's merely a question. The answer may be in the electronic library of the globe, or that old dusty paper library; or you can call Kodak -- the pro service reps. only sit around anyway. I know you've got their number, Kostas, because it's not at my fingertips.
If you are starting a thread, and are just curious, you are opening an old can of worms about how emulsions are made, and how filters effect certain molecule structures in multigrade or variable contrast or poylcontrast papers. It then goes into what papers you use, and therefore what the filter colors do when interchanged or combined.
You've got, basically, a cyan and magenta filter. If you combine them you get a tan filter, if you double up you get a lesser 'grade' esposure. I forget where this goes, from my own research, years ago; but as I said . . . I simply went to the ole blue and green.
Then, finally found I was always using one of three grades, so bought paper accordingly. I stopped doing split grade light, and went to two different developers as in the De Beers formula.
I would like to hear what you have in mind.
S. Shapiro
----- Original Message ----- From: Walter Holt
To: List for Photo/Imaging Educators - Professionals - Students
Sent: Sunday, January 16, 2005 3:43 PM
Subject: Re: Enlarger filter question
Jim,
You are preaching to the choir. I fully understand what you are saying as I started using VC paper in 1959 (DuPont Varigam I think).
I was not the one asking about the blending or adding of VC filters, that was Kostas. Personally I think it would be a poor idea.
In my own darkroom I Use an Ilford Ilfospeed Multigrade enlarger head and control box. I just punch a button to change contrast. I am not unsure, but I do experiment experiment, and have fun.
Walter
======================================================================================================
On Saturday, January 15, 2005, at 06:44 PM, Jim Thyer wrote:
Walter,
I am not sure you are correct in your description.
Consider what each filter does, remembering NO FILTER corresponds to grade 2, but as the filters are designed to work with a uniform exposure time (from 0-3 1/2 grades) there must be some neutral density as well as the yellow or magenta filtering to maintain the same exposure times. Low contrast filters use yellow, to filter out the magenta, so adding No 1 plus No 2 filters gives the neurtal density filter (2) plus some yellow (1) resulting in the same amount of yellow filtration but a longer exposure required, i.e. still equivalent to a No 1 filter.
Combining filters with numbers below 2 (yellow) and above (magenta) basically add neutral density requiring longer exposures, with the filter allowing most of its colour through controlling the contrast.
If you tried combining filters 0 and 1, you are reducing the magenta further, but if the 0 filter already excludes all magenta then the addition of filter 1 will have no effect, other than increasing exposure.
Trying the same with filters in the range 3-5 is more complicated, as from 4-5 there is a required increase in exposure time needed for the paper.
My reference to filter 2 being equivalent to no filtration is based on the Ilford Ilfospeed Multigrade II book.
However, as others have mentioned, there are techniques of printing different sections of the print using different filtration to perhaps increase the contrast of just the clouds in the sky, or of split grade printing which uses exposures of Filter 0 to bring the paper to a "threshold point" and then a higher grade to improve highlights. One reference is the book by Harry Fearn, "Better in Black and White" ISBN 1 873319 30 4.I may be able find some further references if needed.
But if unsure, experiment, and have fun.
Jim Thyer ------------------------------------------------------------------------------------------------------------------------------------------------------------------
----- Original Message ----- From: "Walter Holt" <locnleave@xxxxxxxxxxx>
To: "List for Photo/Imaging Educators - Professionals - Students"
<photoforum@xxxxxxxxxxxxxxxxxxxxxx>
Sent: Sunday, January 16, 2005 6:47 AM
Subject: Re: Enlarger filter question
Kostas, I assume your talking about the filters to change the contrast in B&W printing. A #2 plus a #1 would give you a #1.5. Think of it this way, a #2 would give you normal contrast and a #1 would give you less contrast. The #1 filter will lesson the contrast that the #2 alone would have given you.
A #3 filter is more magenta than a #2. Adding a #1 and a#2 will give you less magenta than the #2 alone. A #4 and a #2 would probably give you the contrast of a #3 filter.
A full set of filters should include all the filters from 1 through 5 plus all the half steps between. Walter
======================================================================== ============================ On Saturday, January 15, 2005, at 04:01 AM, kpp@xxxxxxxxxx wrote:
a quick one. Can enlarger filters be combined? i.e. is no1 + no2 together a no3? thanks, kostas
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