[pure-silver] Re: Calibrating a dichroic head
- From: "Rob C" <forum@xxxxxxxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Mon, 26 Mar 2007 22:50:03 +0100
Some further info which you may find useful:
I did some sensitometric testing when I purchased my L1200 and have checked
back at my results. What I found was that the L1200 is a very accurate enlarger
in the sense that it's factory setup for filter dials is very good. The ND
filter is in logarithmic units so each 10 units is 0.1 LogD so you can
accurately dial in ND and adjust time accordingly. It also seems that Ilford
has specified it Y+M figures very accurately for the L1200. So accurately that
on my enlarger using Ilfords figures I got HD curves which all crossed at the
same point on my graphs. That is, the Ilford figures are perfectly speed
matched to the L1200. (not so for other paper manufacturers). I did the tests
on Ilford MGIV FB
The ilford figures for grade 2 are (or were) Y45 + M24. This gave me an ISO
Range Number of 132 which is actually very close to ISO Grade 1. Using just
M130 I got an ISO Range Number of 58 which is around an ISO Grade 5. It should
be noted that modern papers are capable of greater contrast than ISO grades
indicate. Now some may dispute the accuracy of these figures but I'm not
interested in hearing about it because what is most important is that you get
at least 3 full grades of additional available contrast from the Y45 + M24
figures which means that if your neg is calibrated to the Y45+M24 filtration,
then you should have ample additional contrast available. Possibly as much as 4
ISO grades.
My tests gave a print density of .65 as the speed point which for me was a mid
tone around Zone V and NOT zone 7 or 8 which some favour for printing VC
papers. The important thing for me at the time was that I knew where the speed
point was. Now that I use a diifferent method to print it has become irrelevant
to me as I just calibrate neg for printing without filtration and add Y or M as
required and use filter factors to correct time accordingly.
Assuming your dichroic filters are in good condition and the dials are dialing
in the filters properly, then you should get similar results with Ilford papers.
Usual caveats apply. i.e. YMMV, paper type, chemicals, neg development etc etc.
Also note that using only single filters will shorten your print times
significantly for normal contrast prints which will put them on a par with your
condenser printing times.
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