Kodak Color Densitometer

Discussion in 'B&W: Film, Paper, Chemistry' started by MikeK, May 15, 2005.

  1. MikeK

    MikeK Member

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    I now have a Kodak Color Densitometer Model 1. Anyone have any experience with this antique device? It is in very good condition and I do have a very skimpy instruction booklet. I have managed to set the beast up and "zeroed".

    The instruction booklet does mention measuring densities of black & white film but fail to mention what "channel' filter to use. The available filters are Red, Green, Blue and clear. I am assuming for B&W I would use the clear/no filter channel.

    I just ran a quick test using a scrap of J&C 200 developed in Pyrocat 10:10:1000 and the Base+fog had a density of 0.05, the brightest highlight had a density of 1.55 (overcast sky) and the shadow area had a density of ~0.23. Do these numbers seem reasonable?

    Mike
     
  2. John Cook

    John Cook Member

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    I purchased one of these, brand new, in LA upon graduation from art school in 1970. They work remarkably well, especially for b&w zone work. Your eye can match densities with close tolerance. And there is no drifting of the dial with warm-up as with modern electronic units. Just make sure you have the correct bulb, after many years and owners.

    Sorry, I'm not a pyro user so I can't address the readings you obtained.

    With D76, Rodinal, etc. I develop for 0.1 over bd+f for zone one and 0.8 over bd+f for zone seven. Draw a straight line between those two points to get the densities for other zones.

    These densities print perfectly for me with an Omega D5 with a condenser head on grade two paper in Dektol.
     
  3. Neanderman

    Neanderman Member

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    The clear channel would be used for b/w negs processed in non-staining developers.

    For negatives processed in pyro, you should do two readings -- one on the clear channel and one with the blue channel. According to The Book of Pyro, your stain density (measured on the blue channel) should be 40% greater than the density on the clear channel.

    The blue channel reads the "effective" (i.e. what the paper sees) density. The difference between your blue channel shadow density and your blue channel highlight density is the effective range.
     
  4. Kirk Keyes

    Kirk Keyes Member

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    The amount of stain will depend on the film, as some films stain to a much greater extent than others do.
     
  5. NER

    NER Member

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    I have the same densitometer. I'm not sure what you mean by "shadow area," and we don't know what filter, if any, you used to read the reported densities, however we can be reasonably sure that 0.23 must be higher than Zone I if your B+F density is 0.05 (which seems low to me, but then I don't use the film you mention). Not knowing what Zone your high value falls on, we can't say whether that number is reasonable. If it corresponds to a Zone VII density, your CI based on those numbers would be about 0.73, which is a bit higher than some would prescribe, even for cold light printing, but it may be right for you given your printing process(es) and objective(s).
     
  6. MikeK

    MikeK Member

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    I made the measurements without any filter. The shadow area was an area where I could just make out detail. Not very scientific I know. Does anyone know if you can get a calibrated negative I could use to get up to speed on?

    Mike
     
  7. NER

    NER Member

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    Sorry, I don't know.The blue filter, by the way, is indeed the one you want to use for reading stain + silver density.
     
    Last edited by a moderator: May 16, 2005
  8. John Cook

    John Cook Member

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    Mike, I'm not exactly sure how you would use a "calibrated" negative. But two possibilities come to mind.

    First, to check your densitometer's accuracy, you can get some Kodak 3" ND gels (I hope they still make them). See if the density reading you get matches the nominal density of the gel you are reading.

    Second possibility is to do an old-fashioned "Nine Negative Test". Ever hear of one of these? It will challenge your bookkeeping skills more than your photographic ones.

    Set up a "standard" target, such as the head and shoulders of your wife, holding a gray card under her chin, with a new white bath towel draped over one shoulder and a black towel over the other. This gives you skin, middle gray, textured black and textured white, all in one shot. Pose her outdoors in sunlight under a clear sky.

    Shoot three sheets at normal manufacturer's ISO, three sheets at perhaps a half or two-thirds over-exposed, and another three sheets the same amount under exposed.

    Then develop one sheet from each exposure group according to the developer instructions. Another group of three perhaps forty percent under (by time) and the last three forty percent longer.

    With great patience and care, make the very best print you can from each of the nine negatives with your enlarger, favorite paper (grade 2 only) and developer. No heroic measures like excessive burning/dodging, Selectol Soft developer, bleaching, etc.

    Then lay out the nine prints and study them. The one you like best represents your personal exposure/development for that film on a nice, sunny day.

    Once you have these figures, you can then do a typical zone system exposure test using a gray card as your target, with the ISO speed and development time which you chose from the Nine Negative Test. Plot the densities obtained from these exposures to get your perfect curve which prints best on your equipment.

    When testing future films and developers, you need only shoot a few frames of a gray card and see if the zone densities fall on your perfect curve.
     
  9. L Gebhardt

    L Gebhardt Subscriber

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    Look for a Stoufer step wedge. They are available from many places.