Neutral density with colour heads

[MurrayMinchin]

I'm 99.9% sure I'm going to get a colour head (Beseler 45s for a 45MXT enlarger) for printing B&W VC paper. I like to print some negatives at 5x7 and am concerned about print exposures being too short, or having to use too small an aperture.

Am I right in thinking that (after finding the correct contrast settings which result in too short of an exposure) dialing in equal amounts of cyan, magenta, and yellow filtration wouldn't change contrast but would be the same as adding neutral density, and result in comfortably longer printing times?

Murray

 

[Dave Miller]

That’s the theory Murray, a little testing will be required to verify the setting. You don’t say which size negatives you intend printing. If it’s any help I make 7”x5” prints from 6x7 negatives on my Durst 1200 enlarger at f16/f22 around the 10/15 second mark. If you do find your printing times are too short then you can screw a standard ND filter to the enlarger lens to achieve extended times. I don't think you should worry about stopping the lens down, again a simple test will show that any half decent enlarging lens will produce good results at minimum aperture; try before assuming that it won't.

 

[Andrew Kleinfeld]

Cyan alone will do the job, not confuse you on yellow and magenta settings for contrast.

 

[Mick Fagan]

Give or take, the dichroic filtered diffuser enlargers that I have used, work out at approximately one stop of density for every 30 units of CMY.

Meopta enlargers are really good, they have an ND filter built in.

Unless I'm running at the extreme of contrast range wringing every last bit of high or low contrast, my enlarger always starts with 30 units of density for a 1 stop exposure difference.

This allows me to run through a set of negs from a contact sheet using the same contrast setting. If one neg is a 1/4 stop lighter or darker from the majority, then all I have to do is move all three filters the appropriate amount and print.

By running at 1 stop in, I have the advantage of a 2 stop range.

For your purpose of making your exposure times longer, just pick a figure and run all three filters to an equal setting. From there you can then change the M & Y filtration to get your contrast.

I have found this to be true with my LPL 7700, LPL 7451 and my current DeVere 504, all fitted with dichroic colour heads.

Mick.

 

[MurrayMinchin]

Thanks guys

(Dave - I'll be using 4x5).

Murray