Dichroic Filters & VC Papers

[Pawlowski6132]

So, I'm confused (what's new)...in the manual of my Omega Dichroic head, it gives a filter combination that is equivalent to a #2 print filter (if i'm interpreting this correctly.) So, I assume that with my VC paper, that I should always start printing with those filters in place.

Then, I notice on the Freestyle website that to emulate a Grade 2 paper that filters should be set at 0.

Does VC paper have a default value that correlates to graded paper?? It must right?

This seems like such an obvious question, I'm embarassed to ask it but...

:o

[Drew Wiley]

To me, having all the Chromega filters set on zero is just about perfect for grade 3.
Lots of the time my favorite graded and VC papers print ideally with no changes to
the colorhead, and just the variable of developing time. My negatives tend to be very
consistently developed, so I usually need to add a little Magenta filter contrast only
when the degree of enlargement gets unsually high, like printing from little 6x7 or
35mm negs. Or sometimes I like to do split printing between M and Y for local contrast
tweaks. With VC paper, I never pay attention to "grades" or premeditatated filter
settings. I just do it.

[Larry Gebhardt]

The Omega filter combinations are trying to balance the speed as well as the contrast of the paper. You really only need to use one filter at a time (Y or M) to get the full range of contrast your paper is capable of. But as you change them your speed will change noticeably. Don't let that concern you. In my opinion you should always make a new test strip after changing the contrast, so speed matching provides little benefit.

Grade 2 will be about at the zero filter position for most papers, but to be sure you would need to test it. That's not needed though as you don't really care what grade you are printing at, only how the image looks. Balance your film development to work with no filters, which will be about grade 2.

[percepts]

yes its a simple question but a good one with a tricky answer. There's more than one way to skin a cat.

zero filtration means use the papers natural contrast range which is around grade 2. As others have already said, the easy way is to use only one filter at a time so either just yellow or just magenta. Yellow softens contrast. Magenta hardens contrast.
But filters have density and as you dial them in they require an exposure time adjustment to compensate for that density just like the filter factor on a lens filter.

The question is how much factor. Well Yellow requires very little. Magenta siginificantly more. How much for your enlarger? I don't know but if you only have small contrast changes of 5 or 10 units it will only be a very small difference to print.

For my Durst L1200 Yellow goes upto a maximum of 1.2 filter factor and magenta goes upto a maximum of 2.2 filter factor. Your manual may have the filter factors in it.

So to get round the exposure time compensation problem, the paper manufacturers give combined Y+M values. The idea is that these values are balanced for total filter density so that when you change grade you don't need to change exposure time.
Nice theory but.... The contrast curve for each combined Y+M value should all intersect at the same point. However, in reality that never happens unless you have carefully calibrated your enlarger to make it do so. Also you need to know what print density that crossover point is (speed match point). And you need to be able to accurately judge it on the baseboard. And it may not exist in your print. And as paper ages it moves density. So speed matching with combined Y+M filtration is not an exact science so you always need to tweak exposure time when you change print contrast.
As a result, a lot of people decide that its not worth the hassle of using combined Y+M and just use single filters and adjust time using known filter factors (learnt through experience).

Having said that, if you know where the speed point is and your Y+M values are well calibrated then it does make life easier. Ilford multigrade filters on MGIV are extremely well speed matched to a print density of around 0.3.
My Dursts dichroic filters are speed matched to around a print density of 0.7 (middle grey) using Ilfords Y+M figures on MGIV.

For your enlarger I have no idea what the speed match point will be for Y+M values.

Note that the speed match point may be different for different papers.

So take your choice. Single or combined. With single you can forget about speed matching and just add yellow or magenta as required to taste. With combined you need to do tests to be sure where speed point is and that it is same for each combined setting otherwise unexpected results can lead to frustration.

[Wade Guisbert]

Pawlowski6132

NEVER NEVER think you hace a dumb question! I was glad you asked. I learned something valuable too!

[ic-racer]

The mixed filtration values are for 'constant exposure' as you change contrast. Otherwise you can use no filtration for #2 or so and add M for more contrast or add y for less. But you need an exposure correction factor for each change.

[Vlad Soare]

I found that negatives that print well on normal grade paper need about 45M (on my enlarger - yours may be different) on variable contrast paper.
I noticed the same with my older enlarger, when I used to use separate gel filters placed in the drawer. Printing a negative with no filter in place gave me noticeably lower contrast than printing it with a 2 1/2 filter.

I think this is caused by the low color temperature of incandescent bulbs. It's kind of a built-in yellow filter.

Expecting a VC paper to give normal contrast with no filter in place is a common mistake. Normal contrast requires a little magenta. In fact, if you look at a set of gel filters, like Kodak Polymax or Ilford Multigrade, you'll see that no. 2 1/2, which is usually regarded as a "normal contrast" filter, is actually magenta, not white.