Limiting light output...
I've started playing with contact printing my 4x5 negs for fun. My printing experience (was) extremely limited, but after some time I got good output and am pleased.
Except for one thing....
My bulb is a 15w bulb, in a desk lamp with a rounded cone (sort of a parabola shape), about 3' above the negative.
The printing paper suggests a 7.5w bulb at least 4' above the paper, but I couldn't find anything quite that week.
My exposure time on thin negs is about 1s, dense negs about 5s. I'd like to slow the process down, so that even the thin negs require several seconds of exposure, so that I could burn and dodge.
Any ideas on a cheap simple way to dim the light? I was thinking nuetral density filter - perhaps a tinted shield from a motorcycle helmet, cut to shape and taped in place on the lamp (since the exposure will be short).
Any better ideas before I spend money?
Move the bulb. Say lift it to 4.5 feet.
Remember light increases/decreases with the square of distance or something like that -)
I'll try that first. Just gotta think on how... it's in the bathroom, on a countertop, so I'll have to put a box under it or something.
I know you can buy 7.5 W bulbs with a standard household screw base, that would give you a little less light. Years ago I did some contacts using a radio pilot light type bulb hooked to an old toy train transformer from my (massive) junk collection -- that makes it almost point source.
(Of course I am a compulsive tinkerer. )
Weston had his bulb on a peg board so it could be set at different heights (you could even space them by stops if you wanted), and he had some cloth over the bulb, which must have acted both to diffuse the light and reduce output.
If it wouldn't generate too much heat and present a fire hazard, you could put one or more layers of cloth or paper under the bulb.
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7.5W bulbs are available. If the "desk lamp" in plugged into an outlet, you could also buy a dimmer, perhaps incorporated into an extention cord, that would give you quite a bit of control over the level of light.
Have you tried bouncing the light off the ceiling?
Thanks for the ideas.
Going to try, in order:
Bouncing light off ceiling because it's easiest. If that doesn't work, then:
Find a 7.5w bulb. If that doesn't work, then:
A variant of David A. Goldfarb's idea... I'll try to restrict the light by making an aperture. I know the opening size of the existing cone, I can calc out a circle with half the area and thus half the light. Since we're talking just seconds, and the 15w bulb doesn't generate much heat, it should be OK.
I had the same problem w/my omega B-600. I shot some B&W 4x5 exposures of a flat white wall using the negatives to create a neutral density filter and cut and inserted the 'filter' in the enlarger. Exposure times are now up around 4 sec for Ilford MG IV satin and about 8 sec for MG wartmtone glossies.
John - good idea.
But bouncing the 15w light off the ceiling worked like a charm. Negatives that are very dense (very overexposed winter scenes) around 20s, normal density negs about 5s, thin negs around 1s.
Thanks, all - good to have reasonable times & control.