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From: donl@foist
Newsgroups: rec.photo,sci.electronics
Subject: Re: Homebuilt transmission densitometer?
Summary: Transmission densitometers
Message-ID: <10692@sgi.SGI.COM>
Date: 9 Feb 88 23:40:08 GMT
References: <2659@dcatla.UUCP>
Sender: daemon@sgi.SGI.COM
Distribution: na
Organization: Silicon Graphics Inc, Mountain View, CA
Lines: 31

In article <2659@dcatla.UUCP>, ittfb@dcatla.UUCP (Thomas F. Blakely) writes:
> A handy tool around the Black & White darkroom these days is a
> transmission densitometer.  While relatively inexpensive ones are
> available (ca. $200) it might be an interesting project to build
> one.  Has anyone had any experience along these lines?  It should
> be pretty straightforward, unless there's something I missed.

I use an enlarging meter to measure density, under the enlarger light
source.  I either project the negative or lay it over the photocell.
The meter gives linear values (a function of time and paper speed), so
i take the log myself.

There is an outfit (which seems to be basically one man) called Science
& Mechanics Instruments or something like that, with plans for
densitometers.  The basic scheme is that they will sell you one of a
couple of different meters, and plans for a light source, which is
simply a wooden box with a bulb and brightness control, with a little
stand for the meter and an arm for the probe.

I agree that density measurements don't have to be very complicated,
and it should be easy to build a densitometer in any of several
configurations.  The meter i use, which is also handy for general
printing, is a Beseler i bought for about $75.  It has proven itself
plenty accurate and repeatable for my purposes.  It's a little clumsier
to use than a densitometer, because i have to multiply the ASA dial and
time and then take the log, but for the money, it serves me just fine!

- donl

{sun,pyramid,adobe,decwrl,ucbvax,allegra,research}!sgi!donl
donl@sgi.com