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  1. #21
    RobertV's Avatar
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    They are red sensitive, just not as much as other films
    TONAL is almost RED blind so you can develop this film by dark red X-ray light.

  2. #22
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    How much red light, enough to develop by inspection much like regular prints in safelight?
    Quote Originally Posted by RobertV View Post
    TONAL is almost RED blind so you can develop this film by dark red X-ray light.

  3. #23

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    Quote Originally Posted by hrst View Post
    "Ortho" film usually means it IS spectrally sensitized (with sensitizing dye) for green wavelengths, in addition to blue. Non-sensitized emulsion is blue-sensitive only. Those are also available for some special purposes such as copy films as mentioned before in this thread.

    i didn't realize there were differences, i had thought that photo paper,
    was "orthochromatic" generally speaking because it was not panchromatic.

    hmmm, i guess i was calling blue sensitive "ortho" without realizing there was a difference ....
    so does this mean that photo paper is "ortho" and sensitive to green
    as well as blue, or is it only blue sensitive or something different altogether ?

    early photographic processes that just use silver nitrate ( like wet plate, dry plate ( some ) &C
    would they be considered something else besides "orthochromatic"

    thanks in advance !

    - john
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  4. #24
    JPD
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    Quote Originally Posted by Photo Engineer View Post
    This has come up several times. People have posted the spectral curves of the film and my observation is that these are just poorly sensitized pan films with low red sensitivity. They are red sensitive, just not as much as other films, so the manufacturers had to come up with a name to describe them.
    The ADOX orthopan-films were called "revolutionizing" when they came out in the late 40's because of their sharpness and extremely fine grain. Dr. Schleussner Fotowerke (later called ADOX) was founded in 1860, so they should have had the knowledge about sensitizing film?

    Old german photography books tells about orthochromatic, panchromatic, orthopanchromatic and superpanchromatic emulsions.
    J. Patric Dahlén

  5. #25
    JPD
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    Quote Originally Posted by hrst View Post
    "Ortho" film usually means it IS spectrally sensitized (with sensitizing dye) for green wavelengths, in addition to blue. Non-sensitized emulsion is blue-sensitive only. Those are also available for some special purposes such as copy films as mentioned before in this thread.
    That should be why the swedish flag looks like the finnish one on really old photos, taken with blue-sensitive plates (blue went light and yellow dark), but look swedish with modern ortho film. Green has some yellow in it.
    J. Patric Dahlén

  6. #26
    CBG
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    VC paper has two different emulsions for a different intention than widening the spectral sensitivity.

    VC paper is like having two papers in one, the first a high contrast emulsion, the second a low contrast emulsion. The two different response curves are designed to be complimentary to each other and only exist to give the user contrast rendition choice.

    The prototypical orthochromatic film has just one emulsion layer that is sensitive to a wider spectrum -blue and green and UV - to give a more natural rendition than the plain emulsion that is sensitive only to blue and UV.

    I suppose that with modern technologies, there's nothing I know of that would intrinsically prevent film makers from making a more complex ortho film with multiple layers, but the essence of an ortho film can be expressed with a single layer.

  7. #27

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    Quote Originally Posted by JPD View Post
    Green has some yellow in it.
    Not so. Green is green, yellow is yellow.
    A film that is green sensitive needs another 100 nm or so worth of extended sensitivity to also capture yellow.

  8. #28
    Photo Engineer's Avatar
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    Quote Originally Posted by JPD View Post
    The ADOX orthopan-films were called "revolutionizing" when they came out in the late 40's because of their sharpness and extremely fine grain. Dr. Schleussner Fotowerke (later called ADOX) was founded in 1860, so they should have had the knowledge about sensitizing film?

    Old german photography books tells about orthochromatic, panchromatic, orthopanchromatic and superpanchromatic emulsions.
    You must remember that sharpness and grain have nothing to do with spectral sensitivity. You also have to remember that the German chemists came up with very "non technical" descriptions for their sensitization which we in the US called by name as short and long red for example, replacing the qualitative names assigned by the Germans. This was probably advertizing, as usually, the US companies didn't mention sensitization except in technical articles.

    As for B&W papers, today even the simpler graded contrast papers are ortho sensitive. They are probably made so to match the speed and sensitivity of VC papers to white light (grade 2 normally).

    PE

  9. #29

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    Quote Originally Posted by jnanian View Post
    i didn't realize there were differences, i had thought that photo paper,
    was "orthochromatic" generally speaking because it was not panchromatic.

    hmmm, i guess i was calling blue sensitive "ortho" without realizing there was a difference ....
    so does this mean that photo paper is "ortho" and sensitive to green
    as well as blue, or is it only blue sensitive or something different altogether ?

    early photographic processes that just use silver nitrate ( like wet plate, dry plate ( some ) &C
    would they be considered something else besides "orthochromatic"

    thanks in advance !

    - john
    Exactly.

    The "native" form starts out without any spectral sensitization.
    Those are "unsensitized" or "blue sensitive" and may be sensitive mostly to
    UV and some blue. (Ordinary B/W photographic papers, salt prints and siderotype processes belong here.)


    If you sensitize for green the material becomes "orthrochromatic".
    (MC/VC photographic papers fall into this category.)

    If in addition you also sensitize for red,
    the material can be called "panchromatic"
    (There used to be a few panchromatic b/w papers
    for printing b/w prints from color negs.
    Total darkness was the best safelight.)
    Last edited by Ray Rogers; 02-01-2011 at 11:11 AM. Click to view previous post history.

  10. #30

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    it never ceases to amaze me how complicated
    the simple ( looking at least ) things we take for granted are.

    thanks for the help on this, i have a little more of a clue now
    but that said, i will be the first to admit, i am still pretty clueless
    if my apug gallery looks empty you might check these places

    website
    blog
    sell-site

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