[pure-silver] Durst L1200 (condensor) & uneven illumination

( 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
============================================================================================================To
 unsubscribe from this list, go to www.freelists.org and logon to your account 
(the same e-mail address and password you set-up when you subscribed,) and 
unsubscribe from there.

Other related posts: