P3D Re: pan, ortho and "regular" films

[Rob <lilindn@xxxxxxxxxxx>]

>
>
> I'm not sure of its background, but I'm only familiar with "ortho" from
> "orthochromatic" film, which is only sensitive to a highly restricted range
> of color, in most cases blue, I believe. Orthochromatic film can be
> processed in a normal ruby-lit darkroom, for instance.
>

       Now that so many people shoot color, and nearly all surviving B&W films are panchromatic, it
seems there is a great deal of confusion about the different sensitivity types of black and white
film.
        Having pre-WWII manuals in my great collection of junk, I'll try to set the record straight
here.
        The first silver-halide films were sensitive to blue light *only*, blind to green and red.
This is why Civil War pictures from glass plate negatives usually feature dark faces, black trees,
and bleach white skies  (I haven't studied the color response of Daguerrotype, but, seeing the
results in portraits, suspect they were closer to panchromatic than early glass plate emulsions).
          Sometime later, an "improved" type of film came out - orthochromatic ("ortho"-correct
"chroma"-color), an inflated name, since orthochromatic films were still blind to red light, but the
fact they were (are) sensitive to green as well as blue was still a great improvement over "regular"
films, as blue-sensitive films were then called.
           Still later, someone finally found a way to make silver halides sensitive to red light,
and we got panchromatic ("pan" - does this mean "wide" or "across" ?) films, sensitive to all the
visible colors of light (note that before there could be color film, a red-sensitive halide had to
be found).  By the late 1950's, panchromatic films had just about completely replaced ortho films.
My 1956 Sears catalog offers Tower Ortho film for little more that half the cost of Tower Pan.  The
1963 catalog has no ortho.
     Rob
    "Everything I have is Y1,96K compliant"
    (which in this case means pan, not ortho :-)


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