LPL C7700MX, dual or single colour filtration?

[gregmacc]

Hi all ... I have the colour head (quartz halogen lamp, diffuser) and have been using single colour (magenta) filtration. This method requires an exposure adjustment with every change in filtration which I find a bit frustrating. Will using dual colour filtration eliminate the need for exposure adjustments?
Ilford's documentation re. their multigrade papers states "Dual filtration values usually need longer exposure times than single filtration values, but need less adjustment to exposure times when changing contrast"
I don't see any advantage to dual filtration if there remains a need to adjust exposure even if that adjustment is "less".
Any thoughts, suggestions, experiences?
Cheers
Greg

 

[dasBlute]

Paul Butzi has an article about running some fairly simple
tests to produce the filter settings for variable contrast printing.

When done, changing the ratio of yellow/magenta changes the
contrast but not the overall exposure time. Have not done this
myself yet but need to. Right now I split filter every print,
even the 'easy' ones... this would make it easier for me...

http://www.butzi.net/articles/vcce.htm

 

[ath]

Will using dual colour filtration eliminate the need for exposure adjustments?

In general: no.
In detail: yes, provided that you define which tone (white, black, middle grey) should not change the needed exposure and you calibrate your system for this.
Every paper / developer combination is different.

Ralph Lambrecht describes in Way beyond monochrome how to calibrate for constant white.