[pure-silver] Re: Spiratone 200 C Enlarging Meter Instructions
- From: "Nicholas O. Lindan" <nolindan@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sun, 28 Oct 2012 18:03:41 -0400
"Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
Nicholas Lindan makes an enlarging [meter]
of very good repute. I would hate to disagree
with him about the tenth stop criteria
[for print exposure] but I would like to
see that in practice.
Like most things, one gets there by degrees.
1/4 stop (~20%, or the difference between
20 and 24 seconds), I think we can all
agree, is just a little bit too coarse
So, make it half that - 1/8th or 10% - but
as one needs to add things in one's head and
most people work in base 10 we come to 1/10th
of a stop of the f-stop timer.
With #2 paper a 1/10th of a stop (20 -> 22
seconds) is just discernable in the clear light
of the next day when looking at the dry prints.
2/10th (close enough to 1/4) is discernable.
With grades 4 1/2 and 5 a 1/10th of a stop
is easily noticeable. 1/4 stop is the difference
between OK and unacceptable.
Now, to control to 1/10th of a stop you need to
measure to at least twice that, or 1/20th of a
stop.
Another matter comes into play - determining
the correct paper contrast. One should use the
important tones in the print to find the right
paper grade. To do this means, often, metering
ZIV and ZVI, tweaking the grade and exposure for
the highlights and resigning oneself to
dodging/burning the shadows if needed.
Testing showed that 1/20th of a stop resolution
just wasn't enough. Ergo, the meter measures
in 1/100th of a stop which is around 1%. Again,
people are happy working in decimal and so a
reading of 4.93 on the meter is a comfortable
displayed value.
Look at it as measuring 10 inches to the closest
1/8th of an inch - that's pretty coarse. Though
1/100th of a stop may sound like massive overkill
at first, it really isn't.
Mention was made of my PSPE prints - those prints
were all made without any test strips: load the
negative, adjust the magnification, meter, print.
It takes some practice to get proficient at
visualizing the print you want. Like all
automation the meter will give you what you
ask for, which isn't always what you want.
When printing a negative for the first time you
should expect to make a work print or two if you
are aiming for a quality print. And there is
always the 'negative from hell' that requires
endless work prints and test strips and
metering just doesn't seem to do much good.
Calibrating a meter a paper is most easily done
by making a grey-scale test print at equal stop
exposures. This gives you a visual scale to work
with: pick the tones you want on the print and read
off the required exposure.
There is an application note for making and using
a grey scale strip on the Darkroom Automation web site
http://www.darkroomautomation.com/support/zonestrp.htm
The technique works with all enlarging meters - some
better than others, naturally.
--
Nicholas O. Lindan
Darkroom Automation
A Unit of Cleveland Engineering Design, LLC
Cleveland, Ohio 44121
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