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Old March 8th 12, 03:54 PM posted to rec.photo.darkroom
Jean-David Beyer
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Posts: 247
Default Metering for B/W Films

Darkroom User wrote:
There are many discussions on the internet for using lightmeters,
either reflective or incident. Much of it for digital or color
reversal films.

When it comes down to B/W films, methods such as the zone system or
BTZS are mentioned.

How do the visitors here like to use their lightmeters for exposing
B/W films for enlarging or contacts in the wet darkroom?

I have two lightmeters. One is a Pentax digital spot meter modified by
Zone VI. The other is a Luna-Pro-F that is either a reflective meter or
an incident light meter, depending on whether the white dome is over the
cell or not. It also works as a flash meter.

Normally, I shoot outdoors and use the spot meter, using the Zone
System. I carry the Luna-Pro as well as a backup. This saved me once
when I forgot to change the battery in the Zone VI, and it went dead on me.

When shooting with electronic flash, I use the Luna-Pro-F in flash mode,
usually incident readings.

It is important to know what the meters are doing, especially if you
have more than one, or you will drive yourself crazy. They will seldom
read the same, and the differences are more than just the different
sensitivity to the illumination. That could be simply calibrated for.
They are also different to different colors, and unless you make a very
careful test, this is impossible to calibrate for. What I did (once: it
is a pain to do it multiple times), was wet up an 18% gray card and
illuminated it from a blue sky. The illumination was not changing during
the test. The gray card was the same color from test-to-test, and was as
good a standard as any. Especially since I normally shoot in black and
white. For that I could get a bunch of meters to read the same. One
camera meter had a CdS cell, and the rest were silicon, but with
different color response curves. The Zone VI is allegedly calibrated so
the film sees what the eye sees, or something like that. But that would
depend on what kind of film was used, and I suppose Fred Picker used
either Tri-X 4164 or maybe Plus-X 4147. Since I shoot TMax, it will have
a different curve. I doubt this matters very much because the saturation
of colors around here is not very great.

At first I was surprised that the Luna-Pro gave different readings for
incident light and for reflected light from the gray card. This was when
reading incident light with the sun in the sky. I then figured out how
to do the measurement when the meter and the gray card could not see the
sun. Then the meter read the same incident and reflected. Wow! The
subtleties will get you if you have more than one meter.

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