Enlarger lamp & graduationgreenspun.com : LUSENET : Large format photography : One Thread
Hello from Karl
I have a 2nd hand Durst Laborator 1200 previous to this,I used a Durst colour head M670. With my previous enlarger I had exposure times, to use a specific example, of 2min 40 at f16. Now I have exposure times of 12min at f16, for the same neg. The bulb is a 150W, it has a white covering. Could the bulb be old therefore giving out less light than the previous bulb.
Secondly, on my column there is a graduation in inches and centimetres. There are also graduations which I assume allow for exposure increase calculations with increasing height of the column. Invers square law. The problem is, I don't know how to use them. Please could someone assist me.
Cheers and thanks Karl
-- Karl Beath (email@example.com), November 15, 2001
I don't think that the bulb is the problem; most probably, you are not using the good condenser/lens combination. In this type of enlarger you must use a particular set of condenser elements for each focal length (50, 80, 150) of the enlarging lens.
-- matthieu ls (firstname.lastname@example.org), November 15, 2001.
Do you have any good reason to play at f/16? Durst enlargers alignes quite well so you may be confortable working with wider apertures. Short lenses usually work fine at f/5.6 or even less, while the bigger ones (135/150mm) are OK at f/8. You may also try Chyoda 250W bulbs, with the side benefit of being larger and providing better light eveness. Although I never use the column numbers it's understood that exposures will change in the same order as the square-to-distance table you find on flash exposure guides. I mean, as the picture's area doubles the exposure gets four times bigger. And so on ...
Good printing. Cesar B.
-- Cesar Barreto (email@example.com), November 16, 2001.