Adding Diffusion to an Omega DII Enlarger
I have an Omega DII enlarger. It uses condensers, of course, which can sometimes create spotting, magnify dust particles on the print, etc. Someday, I would like to get a cold light head to help prevent some of these annoyances.
I have heard, however, that you can make very similar results to that of a cold light with the use of a condenser enlarger by adding a translucent piece of glass or plexi-glass.
Does anyone use this method?
Where would I place this piece of glass on my Omega DII (very similar to the D2)?
What dimensions should I have the glass cut for easiest use?
How "milky" should the glass be?
I assume I can get a piece of glass like this at a home depot.
Any thoughts would greatly help. Thanks.
I would use a 1/8 inch thickness of opaque acrylic...available from acrylic wholesalers. Insofar as placement, it would go beneath the lowest condensor. Ideally it would be circular and install in the metal collar.
Originally Posted by Huram
Regarding the degree of opacity, it should provide for the presention of a smooth textureless light source to the negative.
There is an obvious tradeoff in doing this...as opacity increases due to thickness of the material so will light loss through the diffusion panel
I tried this also. I placed it right above the negative carrier, and on my Durst 8x10 it was about 1/2" above. Any closer, and if there is any texture on the plexi, it may be in focus.
The 1/8" plexi cost about 3 stops of light, which was just too much loss.
So I found a piece of 1/16" HDPE. This comes on large rolls, and a local plastic shop had some scrap. It cost over 1-1/2 stops of light. The diffusion was fairly even, as good as the thicker 1/8" plexi. This is what I would use if I wanted diffusion.
I also tried some 3 mil frosted drafting film (mylar), frosted on both sides. The light loss was about 1 stop, but it wasn't even and showed hot spots. I'm still not sure why it displayed hot spots, but it did.
For about $100 you can buy an omega cold light. I dont think any of the make your own diffusion approch work very well.
I tried several of the above installations on my ancient Omega-II and none of them are as good as none at all. I solved my non-uniform field problems by first, changing the position of the condensers. Someone had nicked the surface of the lower lens (probably trying to use "home-made" negative carriers), and swaping the two lenses solved that problem.. The same guy substituted a "plastic" receptacle in place of the original ceramic. Changing the receptacle corrected the problem. The position of the light source seems to be critical. I am still in search of a “better” source but I don’t want to get into voltage timers et c. If I wanted a computer operated enlarger, I would do the digit thing,
I love the smell of fixer in the morning. It smells like...creativity!
Truly, dr bob.
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I'm considering that move with my Omega B8; the 6 x 9 D2. I've
Originally Posted by Huram
another reason though; contrast reduction. I've read many posts
which credit a diffusion enlarger with lower contrast prints, all things
being equal. A quick conversion from condenser to diffusion would be
another tool to use for whole print contrast control. Graded papers,
which allow for a very high level of room lighting, are my choice.
I think ground glass may be the best choice. Consider the use of
two or even three sheets. Removal of the condensors would likely
result in too great a drop in light output. Dan
Keep your eye on eBay; I picked up an Aristo cold light head for my D2 for US$62. They do come up from time to time. (Interestingly, they seem to come up in "bunches"...none for a while and the three or four all at the same time.)
Film is cheap. Opportunities are priceless.
There does seem to be a rush to suddenly diffuse somehow condenser heads all over the world. I've just started using an oversized condenser head, and removed the cold cathode even though it's light was perfectly even. This started out as an experiment but I reckon the cold light will never make it back to the enlarger! Condensers - to me - do good things. My negs are never contrasty through development so straight away they suit condensers, there is a crispness of fine detail (and grain) and tonally I would say a well set up condenser head is better than a cold light. The exposure times are less, there is no warming up of the light (a pain in the £rse) so a test strip is much nearer the final print. Only real down side is the spotting out of prints - there is more. much more, but if you dont mind that too much I would stick with those condensers!
Both I and Mr. Huram, the OP, are interested in keeping the
Originally Posted by richard littlewood
condensers where they are. He, for less spotting, and I, for contrast
control, would like a way to make diffuse that beam of light emerging
from beneath the bottom condenser. Diffuse so that the negative
sees the light as though from a dichroic head's mixing box.
In grade how much of a contrast change do you estimate was made
by the diffusion to condenser conversion? Dan
It's tricky to say exactly how much contrast differs between condenser/cold light as the colour of light has an influence (multigrade paper anyhow) I think though it is unrealistic to expect a cold light head, or diffusing a condenser head to give a lower grade of paper effect. I found my cold light head sort of flattened highlights (forte paper especially) a little, and was less able to give me detail in lower tones, but as I said my negs are developed if anything on the flat side so they go well with condenser light. If you develop negs on the side of increased contrast a diffused light may well be just the job - although expect softer looking grain. Having both types of light is ideally the best but apart from the rotten spotting out I'm a condenser convert!