[pure-silver] Re: wiring diagram for Devere 108S?
- From: Claudio Bonavolta <claudio@xxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Fri, 16 Nov 2007 16:52:15 +0100
----- Message d'origine -----
De: Shannon Stoney <shannonstoney@xxxxxxxxxxxxxxx>
Date: Fri, 16 Nov 2007 09:24:48 -0600
Sujet: [pure-silver] Re: wiring diagram for Devere 108S?
À: pure-silver@xxxxxxxxxxxxx
>> More "modern" enlargers often use things like stabilized power
>> supplies and low(er) voltage halogen bulbs. My Durst G139 with its
>> CLS1000 head has one of these stabilized supplies.
>
>Somebody told me recently that that is only really important when
>making color prints. Is that true?
><snip>
>--shannon
Stabilizing the light output helps also in B/W because the negative has a low
contrast (gamma around 0.60), the paper is pretty contrasty, that is a small
variation of the exposure makes a bigger effect on the paper.
I've decided to stabilize my enlarger once I was trying to make some tests and
did realize that various "same" exposures were giving sensibly different
densities on the paper.
Since my voltage is stabilized, my prints are much more consistent and I lose
less time in trials.
In color, you have another effect in that a lower voltage gives a warmer light
and may affect color filtering too.
Color negatives are also of low contrast and their paper is also pretty
sensible to exposure differences.
With slides, exposure error is much less sensible because the slide has a
natural high contrast and thus the paper is of a very low contrast.
Note that voltage stabilization is the most effective with halogen/tungsten
light source.
With cold light heads, light output stabilization (through a cell and
electronic loop circuit) is better but the approach I prefer with cold light
heads is to keep the light on and use a lens with a shutter.
Claudio Bonavolta
http://www.bonavolta.ch
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