From: Craig Zammiello (zamm@optonline.net)
Date: 02/15/03-01:48:17 PM Z
----- Original Message -----
From: Richard Sullivan <richsul@earthlink.net>
To: <alt-photo-process-l@skyway.usask.ca>
Sent: Saturday, February 15, 2003 2:01 PM
Subject: Re: operating a Macbeth ST102 Densitometer
> My Brumak has a "slope" adjustment. You first zero it with the "zero" dial
> and then adjust the slope. The Macbeth may be different however.
Richard and Bernhard,
Exactly, the densitometer must be adjusted to zero.
With old analogue MacBeth models you had to calibrate the zero mark in the
back of the machine with a screwdriver. There is usually two screw
adjustments back there, one for zero and one for fine tuning "known"
densities for that particular machine. When the machine was purchased new it
came with a Macbeth step wedge, two or three steps that had written on them
the true "known" density for that machine compared to the actual density of
that given film wedge.
Every time you moved the machine, or if it was not in use for over a month
you were supposed to reset (in the back) the zero point, then test the known
density strip and calibrate the fine tune set screw to that. Don't confuse
these calibration screws with the calibrating knob in front of the machine.
That one is to calibrate the machine's meter to zero each time you turn it
on and let it warm up for 5 or so minutes. Simply press down the lever like
you were taking a density measurement without any step wedge or film in it
and turn the knob until the meter reads zero. You will find this wont go out
that much.
Best you can do without the original test strip is to press down the lever
(without anything in it) calibrate to zero with the rear set screw, and then
use the machine as usual, remembering to use the front knob to check zero
when you warm up the machine each time. I think for most of our purposes it
will work quite nicely.
Cheers, Craig Z.
This archive was generated by hypermail 2.1.5 : 03/04/03-09:19:09 AM Z CST