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vanannan
10th January 2010, 10:33 AM
Hi
I have a Durst easy colour calculator which includes a scale for calculating the increase in exposure times required for any increase or decrease in dichroic filter settings on Durst enlargers, is anyone aware of a similar thing for use with devere dichro filters? or does anyone have a list or formula for the time compensation required.

Thanks

Dave miller
10th January 2010, 10:42 AM
We do have an article on this subject that whilst not being quite what you are looking for may be of help. See: Calibrating Colour Heads for VC Papers
(http://www.film-and-darkroom-user.org.uk/forum/showthread.php?t=181)

vanannan
10th January 2010, 11:15 AM
We do have an article on this subject that whilst not being quite what you are looking for may be of help. See: Calibrating Colour Heads for VC Papers
(http://www.film-and-darkroom-user.org.uk/forum/showthread.php?t=181)

Thanks Dave and obviously to Les, I was thinking of doing similar tests to determine the filter factors I guess I am just being tight (paper costs), I have a densitometer so it should not be difficult and I will get a more accurate result than with any manufacturers calculator.

Thanks again
Regards
Tony

JimW
10th January 2010, 04:29 PM
This any use? http://www.darkroomagic.com/Library/ImageMaking/DualFiltrationGrades.pdf
It came from http://www.darkroomagic.com/

Argentum
10th January 2010, 07:15 PM
the following is a chart for durst L1200

Filter factors (http://www.film-and-darkroom-user.org.uk/forum/attachment.php?attachmentid=159&d=1235698850)

I suspect you will get something very similar from a devere.

You may be able to plot some points using a digital spot meter on your baseboard and dialing in filtration. The yellow is problematic but if you take 5 unit increments upto 70 and then maybe 20 units increments after that, you should be able to plot a chart with a smoothed line in excel and just read of the incremental points.
Is the devere a 200 unit scale (kodak units) or something else like the dursts 130 ?

0.1 of a stop equates to a time factor of 1.071773463
0.2 of a stop equates to a time factor of 1.148698355
0.3 of a stop equates to a time factor of 1.231144413
0.4 of a stop equates to a time factor of 1.319507911
0.5 of a stop equates to a time factor of 1.414213562
0.6 of a stop equates to a time factor of 1.515716566
0.7 of a stop equates to a time factor of 1.624504793
0.8 of a stop equates to a time factor of 1.741101127
0.9 of a stop equates to a time factor of 1.866065983
1.0 of a stop equates to a time factor of 2

infact for the yellow I would take readings at 0, 15, 45, 85, 130 or for 200 unit scale the appropritate equivalent then join up the points with a smooth curve. That will get you pretty close.

vanannan
10th January 2010, 08:36 PM
Hi guys
Thanks for your info, I have spent three hours in the darkroom this afternoon testing my Devere 504 Dichromat head, I have got up to 60 Magenta which gives me an exposure time of 28.5 secs (10 secs no filter) a factor of 2.85, I am a little worried that when I continue my tests and the exposure times increase I will run into reciprocity failure, I have considered opening up a stop but fear this may complicate matters, does anyone know the reciprocity characteristic for Multigrade IV RC.

Thanks again:)

Tony