Multicontrast filters for 8x10 printing

Here are my graphs I made up so that I can print the way I want to print. These graphs let me change contrast without messing up my middle values.

The Y axis is exposure with the Blue #80 Roscoe filter doubled on itself. The numbers represent seconds.

The X axis is the exposure with the Green #389 Rosco filter (single).

Each colored line represents a series of theoretical exposures where the middle gray stays constant. (The Yellow line from 21 blue to 42 green is actual data (10 datapoints), the other curves are all calculated assuming no failure of receprocity)

The radial lines are lines of constant contrast. Of course any intermediate value is possible, the lines pictured are just the ones I happened to test. The numbers by the lines represent the density range in log units. It roughly goes from grade 5 to grade 00.

The graph is simple to use. From any point in the graph, to make a contrast change without changing the middle grays, just move paralell to one of the colored lines to your new contrast grade. The graph will then show you the new times for green and blue.

For a density (overall exposure) change, you really don't need the graph, just mulitply or divide each individual exposure by your favorite factor (I usually use 2 for a big change and 1.4 for a small change and 1.185 if I want to make a change I can't see :))

So, with the graph, it lets me print just as if I had a color head, or MG filters or a MG head.

Quote:

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Originally Posted by Nick_3536

Using two of the same filters should be no different then one filter.

The first filter will pass some light frequency.

The second filter will pass the exact same light.

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I can't seem to confirm this. Seems as if Zaka and Todd are saying the opposite. They indicate that combining like filters give additive effects (not extra neutral density). (H.N. Todd and R.D. Zakia, Photographic Sensitometry: The Study of Tone Reproduction)

As an example. If we combine two #80 primary blue filters, the transmission for the blue peak (420) will go from 63% to 31.5%. The green part (520) will go from 15% to 7.5%.

If you compare that with the effect of combination of one filter with a neutral density filter you will see the resulting filter will be different from above. The neutral density filter, by definition, will affect all the wavelengths the same. So, a 7.5% ND filter will make the 63% blue peak go to 55.5% and will make the 15% green peak go to 7.5%.

Bump.

A single #389 and two #80 filters with an Aristo W45 cold light head placing the filters under the cold light head plexi will provide the correct lighting for Split Grade printing; is this correct to date?

I am going to order them from where, B&H or Rosco? Will the filters being taken in and out create dust problems for the negative? Would it be better to put the filter above the plastic and under the actual bulb?

Thanks for the detailed information you have shared with us.

Quote:

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Originally Posted by Turner Reich

Bump.

A single #389 and two #80 filters with an Aristo W45 cold light head placing the filters under the cold light head plexi will provide the correct lighting for Split Grade printing; is this correct to date?

I am going to order them from where, B&H or Rosco? Will the filters being taken in and out create dust problems for the negative? Would it be better to put the filter above the plastic and under the actual bulb?

Thanks for the detailed information you have shared with us.

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Yes, I have not changed from those two for almost a year. Again, there may be other combinations that will work well, once I determined those to give the full range, I stuck with them.

I got mine from my local store, otherwise I would go with B&H.

They are cheap enough that you can try them with a step wedge to confirm and not be out a lot of money of not satisfactory. I had enough to cut both blue filters from one sheet. My impression from studying the spectra graphs on the Roscoe site is that there were perhaps 10 or so filters that would work for the 'high contrast' filter and probably 10 or so that would work for the 'low contrast' filter.

In terms of dust, I had re-positioned my plexiglass diffuser closer to the negative carrier than original. So, now my filter drawer is between the plexiglass diffuser and the bulb.

Those filters tend to really collect the dust.

In terms of getting the filters in and out of the filter drawer, they are too flimsy on their own (for an 8x10 enlarger). I tried a number of things with various levels of success. I tried a cardboard frame, but it needed to be 1/4 inch on the edges and that made it too flimsy. Once it got caught in the filter drawer and I had to take the whole thing apart to get it out.

I settled on using transparent tape to affix the filters to appropriately sized pieces of 'clear' plexiglass. These slide in and out of the filter drawer without taking the drawer totally out. These can get scratches on them, but in my case, they are between the light and the diffuser panel, so the fine scratches are inconsequential.

This board is very, very useful for keeping track of the exposure times. The coordinates of the pin, of course, represent the two exposure times. Since I now do all test exposures with the same color first, that means re-setting the timer quite a bit.

The paper does not care if the high or low contrast exposure is first, but the time/intensity characteristics of the my Aristo 1414 W45 lamp suggest prudence in maintaining the same exposure sequence. Now, I always do the same color first (I try to guess which will have the shortest time, usually blue)
http://img.photobucket.com/albums/v6...ensityTemp.jpg

(error in the diagram title, should indicate Aristo 1414)

Just to add to this thread. In addition to the split grade printing, I want to be able to use the full-set graded Ilford filters. I made this holder for the 6x6 filters. (I have yet to order the filters from B&H.) Should cost about $50 for these filters (as opposed to $210 for the 12x12 filter set)

http://img.photobucket.com/albums/v6...inished1-1.jpg

I use regular blue or green camera filters right on the enlarging lens for split printing.
My coldlight for 8X10 is blue-green, and this works perfectly for every variable contrast
paper I've tried. I usually make the test strips and one full print without any filters first, then dodge/burn or whatever with one or both of the filters afterwards if needed.
Pretty simple once you get used to it, and the result is the same in the end as using
a colorhead.

Thanks, this is the approach I'm going to put to use. I like that 6x6 holder you made. It's nice to hear that you are pleased with the Rosco filters, I'm ordering them right away.

Quote:

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Originally Posted by Drew Wiley

I use regular blue or green camera filters right on the enlarging lens for split printing.

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I looked in to that but the ones to fit my 300mm Rodenstock were quite expensive. Do you screw them into the lens or do you set them on a filter holder.

I also looked into two nice glass 6x6 filters, but again the price was almost more than the entire enlarger.

Another thing I will mention, that has me dragging my feet with buying the Ilford 6x6 filter set. That filter set will not have even exposure times for me. There is an exposure correction needed with each filter (when using my W45 light.)

So, I was thinking again about making a Roscoe 12"x12" set with 90M, 30M, 15M, 15Y, 30Y, 60Y, 90Y and 180Y. (60M too close to 90M needed because of the high contrast bias of the W45). I would need to mount all the filters on plexiglass and determine my own correction table. I would also need to configure some convenient storage mechanism for all those filters mounted on the plexiglass. On the other hand, the Ilford filters are 'ready to go' out of the box and Ilford has already made the correction table. Plus there is a current APUG thread vouching for the safety of under the lens plastic filters, with respect to image quality. So, it is kind of a toss up.