On 2/25/2011 8:32 AM, Giovanni Fiorino wrote:
Problem darkroom: Philips and densitomentro timer. On timer okbut
densitometer do not understand where to place the cell that allows
check the density of the film resulting in the determination of
correct shutter speed (say, more or less correct).
From the first test returns values crock I think too
low (type 3 or 4 seconds of exposure) but I have not risked the
Click on either test.
These are the questions:
- on paper multigrade the densitometer should be placed before orafter the
filter
between lens and paper?
- the density has to be taken on the film reflected on the paper?
I know that the shutter speed is subjective and can be creative but Ineeded
a timer and I found bundled with exposure, so that ...
Thanks for the answers ... John



Hi Giovanni,

First place the cell so as to read the densest part of the
film (i.e., get the lowest value reading from the
densitometer).

Second, adjust the densitometer dials so that that spot
gives a zero reading.

Now, find the least dense part of the film and take a
reading (that gives you the dynamic range of the negative.)

At this point, you need to prepare (or consult, if already
prepared) a chart - crosstable really - showing filtration
on the left side, type of multicontrast paper on top, and
densitometer settings in the middle. Creation of such a
chart takes trial and error, because each type of paper has
different sensitivity. For fixed grade papers, a different
chart is needed as filtration is irrelevant. To obtain the
proper densitometer setting, expose the paper for a
particular filtration until you find the correct exposure
time. Then adjust the densitometer dials until they yield
that time when read at the densest part of the negative.
That is the setting to record for that paper at that filtration.

Finally, once you have consulted your chart, dial in the
filtration, set the densitometer settings, place the cell on
the spot under the densest part of the film, and read the
predicted time from the densitometer.


--
Francis A. Miniter

In dem Lande der Pygmäen
gibt es keine Uniformen,
weder Abzeichen, noch irgend welche Normen,
Und Soldaten sind dort nicht zu sehen.

Siegfried von Vegesack, "Es gibt keine Uniformen"
from In dem Lande der Pygmäen