Archived posting to the Leica Users Group, 2002/08/08

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Subject: Re: [Leica] Colour analysers
From: Rolfe Tessem <rolfe@ldp.com>
Date: Thu, 08 Aug 2002 15:33:02 -0400
References: <p05100302b9774f17aff6@[203.208.68.83]>

- --On Thursday, August 8, 2002 8:28 AM +1000 Alastair Firkin 
<firkin@ncable.net.au> wrote:

> Could any darkroom buffs amongst us comment on the best and most
> versatile colour analysers? I have a Rodenstock CA 30, but the focotar
> does not have a filter thread, and so it has become a real pain to use
> with the V35, and the focometer although great, does not do colour
> channels. Perhaps the Jobo 7000?

I use the Jobo 5100, the predecessor to the 7000, which has more features 
than I even know how to use. I believe the 7000 is basically the same 
machine with an improved interface.

I find that once a good gray channel is set up, it holds for months and 
months. I usually recalibrate when I get a new batch of paper with a 
different emulsion number.

With the 5100, the workflow goes like this:

1. Change to the channel programmed with the gray reference and read a gray 
in the scene. If there is no gray, I put the diffuser under the lens and 
read part of the projected image since many "average" negatives integrate 
to gray in this way.

2. Change filtration to achieve "0" on all three color channels.

3. Change to the channel programmed with negative Dmax, read the 
appropriate part of the negative, and then stop down the lens to achieve a 
convenient exposure time in the 5-10 second range.

4. Insert paper and hit the foot switch connected to the analyzer to make 
the exposure.

I get about a 75-80% sucess rate on the first print when the analyzer is 
programmed correctly. Of the 20-25% first print misses, most are slightly 
off in exposure rather than color, presumedly because the point I read for 
Dmax wasn't quite right.

Hope this helps...

- --
Rolfe Tessem
rolfe@ldp.com
Lucky Duck Productions, Inc.
- --
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Replies: Reply from "firkin" <firkin@balhpl01.ncable.net.au> ([Leica] Re: Colour analysers)
In reply to: Message from Alastair Firkin <firkin@ncable.net.au> ([Leica] Colour analysers)