Adding Diffusion to an Omega DII Enlarger

Discussion in 'Enlarging' started by Huram, Apr 18, 2005.

  1. Huram

    Huram Member

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    Hey All,

    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.

    Dave
     
  2. Donald Miller

    Donald Miller Member

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    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.

    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
     
  3. resummerfield

    resummerfield Subscriber

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    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.
     
  4. Paul Howell

    Paul Howell Member

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    For about $100 you can buy an omega cold light. I dont think any of the make your own diffusion approch work very well.

    Paul
     
  5. dr bob

    dr bob Member

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    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,
     
  6. dancqu

    dancqu Member

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    I'm considering that move with my Omega B8; the 6 x 9 D2. I've
    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
     
  7. Mongo

    Mongo Member

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    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.)
     
  8. richard littlewood

    richard littlewood Member

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    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!
     
  9. dancqu

    dancqu Member

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    Both I and Mr. Huram, the OP, are interested in keeping the
    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
     
  10. richard littlewood

    richard littlewood Member

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    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!
     
  11. TPPhotog

    TPPhotog Member

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    I tried out my latest acquisition yesterday which is a "vintage" condenser enlarger and to my eye it gives better highlights, sharper prints and much more punch than my other enlarger which has a colour head. I think I might soon also be a "condenser convert".
     
  12. Donald Miller

    Donald Miller Member

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    I have had the same experience...I have used cold light heads and diffusion enlargers and bought into the Callier effect that Ansel Adams claimed. Once I tried my Durst condensor I never looked back.

    One could argue that the reason for the "more punch" that you speak of as being due to condensor enlargers typically requiring a negative with less contrast...however what I found is that the local contrast within the various tonal scales was improved...Increased local contrast translates to an improved sense of light from within the print. There is no doubt that sharpness is better in my experience.
     
  13. TPPhotog

    TPPhotog Member

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    Donald same experience here with the contrast, I didn't know the technical part of "Increased local contrast translates to an improved sense of light from within the print". I wish I could post a comparison but the only pictures I have printed with both is of residents with learning disabilities for a gallery I've been asked to put together for our residential home. Only having the condensor for a couple of days I haven't had a chance to print much of my "own stuff". There again I'm not sure if a scan of the print would pick up the subtleties.
     
  14. Ronald Moravec

    Ronald Moravec Member

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    Develope you negs to a lower contrast and you`ll have no trouble with condensers. The only disadvantage I have found is trying to get lower contrast. Diffusion is better, but with 99 % of negs, the prints ar indistinguishable.

    A piece of drafting film above the condensers will lower contrast 1/2 grade.

    Since I started filtering water and air in my film room, spotting has gone to nil. Thats where you attack the spotting problem.
     
  15. richard littlewood

    richard littlewood Member

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    Well said Ronald. I used to teach an adult education City and Guilds photography and most people consistently exposed negs well enough but almost always over developed making contrast control almost impossible. If condensers are frowned on it's too much development that could easily be the real problem. Agree with you over keeping clean although since I've been using condensers spotting out seems to have to be much more precise. I've just framed 3 38x30 inch prints made that way, and spotting them out was a real challenge to my sanity.
     
  16. dancqu

    dancqu Member

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    I can not explain that; the light source itself being so diffuse.

    I think I've room on the bottom lip of my Omega B8's condenser
    holder for an eighth inch thick diffuser. I think a thin diffuse sheet
    could be placed directly on top of the negative carrier. Dan
     
  17. Donald Miller

    Donald Miller Member

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    I imagine that the reason for this is that when one is doing this, you are in effect creating a larger light source by the diffusion. Taking this to the other extreme, a point light source will print with higher contrast and more apprarent sharpness then a condensor enlarger with a conventional lamp..This is due to the relative size of the light source. A point light source will more accurately represent what is on the negative...

    Think of it this way, if you wish, the reason that there is more spotting with a condensor enlarger then a diffusion source is that the diffuse light source of a cold light or a diffusion enlarger present a light source in which the light beams are not aligned. The effects of this are that the scattered light beams of the diffusion source do not pass through the negative in a perpendicular orientation.

    Thus taking an example of a dust spot on a negative, it would be present in both the diffusion source and also the condensor source. It is still present but the light of a diffusion source is passing around the dust and does not show it accurately. This same thing happens with detailed information on the negative...edge sharpness and local contrast both suffer because of this diffusion.
     
  18. pelerin

    pelerin Member

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    Diffusion Material

    Hi,
    Looking for a really nice diffusion material. Might I suggest "Roscolux #115: Light Tough Rolux". This is a really nice material, very effective, and essentially textureless. I have utilized it in color printing and find that it demonstrages a high degree of color neutrality. It is durable, easily cut and inexpensive. If you can't find a local photo supplier it can be had from many theatrical supply houses. Failing that, ask your dealer if they deal with BKA as, even if they don't carry it (or even know what it is) they can order it for you. Tech info can be found at http://www.rosco.com/us/filters/roscolux.asp. Look towards the bottom of the page.
    Celac.
     
  19. Huram

    Huram Member

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    Thanks all for the insights. Yes, the main reason I want to add some diffusion to my condensers is to avoid blemishes on the negatives and I don't have enough dough at the moment for a cold light head. I work with a lot of old negatives (family negs from the 30's - 50's and stuff I collect) -- they usually have more problems than just dust (scratches, micro light holes in the negs, etc.). Of course I could do this type of work digitially (can I say that here even if it is in negative restoration?), except that I don't have acess to any top line computer/printer equipment and I can't imagine a digital print would have anything near the snap and sharpness of the darkroom process. I would prefer to look at a darkroom print (even with blemishes) than a flat digital print (even if it got rid of all the "flaws").

    In an effort to try an assortment of "milkiness," I settled on this Bogen Diffusion Filter pack containing 12 different degrees of frost. I got it from MPEX - http://mpex.com/InventoryListKeyWord.aspx -- item number 500000000001-0000. This past weekend, I experimented with various combos to find pleasing results. It has obviously helped in cutting out some of the scratches and spots, though there is still plenty of crap that shows up on my prints.

    Thanks all for the suggestions and help. I am going to start a thread called "printing vintage negatives, preventing blemishes." Please add your 2 cents to this thread to give me ideas in combating unwanted flaws on my prints BEFORE touching up the prints themselves. Thanks!

    Huram