[pure-silver] Re: Durst L1200 (condensor) & uneven illumination
- From: Georges Giralt <georges.giralt@xxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Mon, 23 Jul 2007 12:45:06 +0200
Hi Cor !
I own a Laborator 1000 and the situation is worse tha yours because the
lamphouse was designed for a 100 mm dia bulb which is not made anymore.
I've tried, with success, a Philips double enveloppe halogen bulb of 95 mm dia.
It makes things in the 3/4 of a stop range, and I've evened the lighting by
inserting a frosted glass PLUS a sheet of tracing paper in the filter drawer
between the bulb and the mirror above the condenser. This puts me in the 1/3 to
1/10 stop range, but reduce the light output very much (a pain with the slow
Forte and Foma papers and the RH Designs Analyser going only to 255 seconds)
Another way would be to put a sheet if translucent Perpex (sp ?) above or bellow
the condensers and see what it does. Doing so you transform your semi directed
light system into a diffusion enlarger. I wonder if you will enjoy this....
Selon C.Breukel@xxxxxxx:
> ( I have posted this message before on APUG, which actually felt like
> betraying the pure-silver list...;-).., I actually like our mailing list
> format better, so it served me right that I got little feed-back on
> this..;-)..), anyway.....
>
>
>
> Hi,
>
> I have been using a Durst L1200 Laborator with a condensor for about 15
> years now (35 mm upto 4*5 inch). I have always been quite happy with
> this enlarger. In the past I have checked the illumination and noticed
> it was a bit off.
>
> Recently I looked in more detail: I used the correct condensors and lens
> (80mm), focused a 6*6 negative , removed the negative, and used a RH
> Zonemaster II in the density mode to check the illumination on the base
> board.
>
> I now noticed that the corners and the side were quite off. The L1200
> has on the side 2 knobs for the lamp postion, and the lamp housing can
> be moved in and out as wll.
>
> The best I could do is roughly the following:
>
> 0.15 0.08 0.16
> 0.08 0.00 0.07
> 0.17 0.06 0.12
>
> (so the middle put on zero, the other figures representing the very
> corners and sides). Initially I mistrust the Zonmaster, I mean 0.1 means
> 1/3 stop and 0.15 1/2 a stop.
>
> I find this alot, OTOH I never realy noticed this when printing
> (probably tells that I am not that a good printer I guess..
>
> So I checked by exposing a grade 5 piece of paper to about middle grey,
> and sure enough it showed the same effect, (although I am not sure if I
> realy see that half a stop difference) the corners beeing somewhat
> lighter.
>
> Somehow I find this dissapointing for such a sturdy enlarge of great
> reputation, you might say why worry if you're happy with prints, but it
> is nagging..
>
> So I tried to diffuse the light between the bulb (a guinine Phillips
> Photocresenta, 75 watt) and the condensor with some milky plastic,
> paper, and even a piece of groundglass. It did not help, and even made
> matters worse.
>
> Another solution would be a diffusion head, a CLS501.
> I happen to own such a head, but I was not too happy with it for various
> reasons.
>
> So any suggestions on improving matters will be greatly appreciated!
>
> Best,
>
> Cor
>
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