Graphs for 2-filter MG or VC printing

[ic-racer]

I would like to share my graphs that I use for 2-filter multicontrast printing.

I use the 'standard' 2-filter aproach but there are times when the blacks are black and the whites are white but the middle is messed up. This can take 2 or 3 steps to straighten out.

With these graphs I can make a contrast change (change both filter times at once) with keeping the middle gray values constanat.

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 parallel 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, in addition to the 'standard' 2-filter technique, the graph lets me print just as if I had a color head, or MG filters or a MG head.

I'm glad to post the info on creating the graph if anyone is interested.

http://img.photobucket.com/albums/v670/ic-racer/FineScale2.jpg
http://img.photobucket.com/albums/v670/ic-racer/ExtendedScale.jpg

 

[Mike Wilde]

Interesting co-incidence

I was just editing a web document to print it on a similar tack.

I found an article on Paul Butzi's web site on calibrating a dichroic with VC paper for constant exposure across grades, by testign and adding in NG with the opposite of yellow or magenta to suit your particular enlarger.

I am goign to do this and then add another column in for dry down for FB paper. The planned twist is to calculate the added NG that is needed to get the dry finished print tone that you want after liking the look of a still wet test print.

 

[ic-racer]

I was just editing a web document to print it on a similar tack.

I found an article on Paul Butzi's web site on calibrating a dichroic with VC paper for constant exposure across grades, by testign and adding in NG with the opposite of yellow or magenta to suit your particular enlarger.

I am goign to do this and then add another column in for dry down for FB paper. The planned twist is to calculate the added NG that is needed to get the dry finished print tone that you want after liking the look of a still wet test print.

I saw Paul's website, and it was the inspiration for this project. I never had a chance to calibrate my 4x5 Dichro heads because the pre-made chart with Ilford Paper Insert works perfectly for me.

I made this chart for 8x10 enlarging with a coldlight. The filters were only $6 each, though, I had to buy a few to zero in on two 'good' colors.