[pure-silver] Re: Calibrating a dichroic head
- From: <C.Breukel@xxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Mon, 26 Mar 2007 17:00:03 +0200
Thanks for the feedback, Rob.
I did make a kind of test print with my calibrated settings : exposing a
strip from a 35 mm negative with one of my kids: I took the right side
of his face (which was in the sun) as the reference, starting at zero
filteration plus 0.45 ND. Printed 6 strips around it ( at 130Y, 60 Y and
30Y; at 20M 70M and 130M plus the calibrated ND). Kinda hard to judge,
but right side of the face looked quite equal from 130Y upto 20M, 70M
and 30M beeing off, but that is no surpise, at hard settings small
differences in time give relative big changes. I am getting somewere,
not there yet though. I surely look into your table!
What's your opnion on my questions on the hardware side?
-I'll have to get used to the noice of the fan, it's not very loud, but
its there.
- I feel a very minor vibration from the fan on the head, but with my
Peak grain focuser looking at the projected image I do not see movement.
- The printing times seem roughly 1-2 stops slower than the condensor
head.
(this is with 35mm with a 6*6 mixing chamber, did not get the 35mm
mixing chamber)
- The dials on the head are very dimly lid, espec. The ND dial (yes I
opened the little flap beneath the dials, as well as switch all filters
away with the lever on the left, but still it is weak)
Thanks!
Best,
Cor
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Sent: maandag 26 maart 2007 16:29
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Calibrating a dichroic head
the old calibrating dichroic head problem....
I tried this little game and found that it was more trouble than its
worth. Thats just my opinion and many others swear by it as a worthwhile
exercise.
However, if you start from zero filtration and add just yellow for
softer or just magenta for harder then all works just as well. But I
hear you say I won't get consistent printing times as I change contrast.
Thats true BUT you have just purchased a very accurate head which, if
its working properly, gives you known filter factor times in the manual
which I have found to be pretty accurate. here they are:
Durst CLS501 Head
Filter Factors
Units Y M
00 1.00 1.00
05 1.02 1.08
10 1.04 1.15
15 1.06 1.21
20 1.08 1.26
25 1.10 1.31
30 1.11 1.36
35 1.12 1.40
40 1.13 1.44
45 1.14 1.46
50 1.15 1.52
55 1.16 1.56
60 1.17 1.60
65 1.17 1.64
70 1.18 1.68
75 1.18 1.72
80 1.18 1.76
85 1.19 1.80
90 1.19 1.84
95 1.19 1.88
100 1.20 1.92
105 1.20 1.96
110 1.20 2.00
115 1.21 2.04
120 1.21 2.08
125 1.21 2.12
130 1.22 2.16
I just printed these out (horizontally) and taped to the front of my
enlarger. I just dial in Y or M to get to where I want to be and if I
need to change contrast then its so simple to work out the adjustment in
print time in your head, the effort of trying to calibrate the dichroic
head just isn't worth it IMO.
so if I was printing at 30M and I change to 60M then I move from factor
1.36 to 1.60 which is increase of 0.24 or 25% increase in time near as
damit and it takes a second to work out.
So why do you want to waste time on calibration which is not accurate
anyway. Why isn't it accurate? I don't know. but I do know that if you
take a couple of points from your calibrated results and redo the
calibration using calibrated points as the starting point, you end up
with different results which should not be the case if the calbraton was
correct.
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