A further note: about daylight vs tungsten. For B&W there is
no difference in the film. Speed differences were really the
differences in the meters used to measure the light. Color film,
at least that for making camera originals (includes reversal) is
different. Its designed so that the reproduced colors look right
in a specified illumination. Tungsten light is reddish, looks
brown in daylight, and this difference is adjusted for in the
sensitivity of the color layers. Generally, B&W film for making
original negatives is intended to produce a reasonable gray scale
tone rendition of color. This does vary with the light source but
the spectral sensitivity of the film does not vary. Where a
correction is desired a filter is used on the camera. For
instance, most panchromatic film has too much blue sensitivity so
a minus blue (yellow or green) filter is used on the camera which
results in a tone rendition closer to what they eye sees. The
spectral sensitivity of both pan and ortho films varied,
depending on the sensitizing dyes used. Some modern films, like
T-Max, have much more uniform spectrial sensitivity than the
older films and do not need filtration for correcting daylight
tone rendition. Also, most older pan films have a dip in the
green sensitivity which T-Max does not have.
In the old days motion pictures were often photographed with
a lot of attention to the tone rendition of costumes and other
parts of scenes. I remember as a kid seeing greenery at 20th
Century-Fox painted brick red because it photographed better than
natural green. So why not use a filter, I don't know but susspect
they could control the tone of the green leaves without changing
anything else. BTW, since color could not be used (for B&W) for
separating actors from the background the sets were painted in
skin tones beige, etc, so that the effect of lighting contrast
could be clearly seen. This may have been Fox practice but its
the place I got to see things.
So much for my wasted youth.
On 10/15/2021 1:33 PM, Garry . wrote:
I think I can confirm Richard's information. I dug through some very old Kodak literature and found some information that long ago Kodak had a blue sensitive motion picture film that is within that ASA speed. It was used for creating motion picture titles, etc. Perhaps because it was motion picture stock, there is no identifying information on the film. Not much information, except it was daylight only film, not tungsten. Understandably being blue sensitive. It was extremely fine grained.
Thinking back on the old RKO B&W movie films and others as seen on television as reruns these days, the titles were always white lettering on the screen. How that might relate to the overall process, I'm not sure.
-----------------------------------------------------------------
*From:* pure-silver-bounce@xxxxxxxxxxxxx <pure-silver-bounce@xxxxxxxxxxxxx> on behalf of `Richard Knoppow <dickburk@xxxxxxxxxxxxx>
*Sent:* Friday, October 15, 2021 4:06 PM
*To:* pure-silver@xxxxxxxxxxxxx <pure-silver@xxxxxxxxxxxxx>
*Subject:* [pure-silver] Re: ISO 4 Direct Positive Orthochromatic film
Also, the films I am thinking about, either direct positive
or the release positive, were not orthochromatic but color blind,
i.e. sensitive only to blue and near UV.
On 10/15/2021 1:02 PM, `Richard Knoppow wrote:
> My memory is not what it used to be so I don't remember
> details. You may know there is an effect where if an emulsion
> is seriously overexposed it reverses the image. This effect was
> used to make direct positive material. I am pretty sure Kodak
> and others made such films for either document copying or for
> making duplicate negatives or duplicate release prints where
> only the original positive was availabe (or from a reversal
> film). I am just drawing blanks on the name of the material or
> even the name of the effect it made use of. I am hoping someone
> else here has enough of a clue to remember. Meanwhile I will
> look at what documentation I have to get a reminder. ISO-4 is
> in the range of fast enlarging paper or positive films. If you
> developed a clip what did you get? If I am right it should have
> come out black and a clip exposed to strong light should come
> out clear.
> It is the term "direct positive" that leads me to think it
> might be this stuff. If, however, its just "positive" its
> probably something like Kodak Fine Grain Release Positive, a
> film originally intended to make release prints of B&W movies.
> This is a very slow film, ISO-4 would make sense for it, with
> an emulsion similar to fast printing paper like the late,
> lamented, Kodabromide. There is likely still data on it on line
> and similar film may still be made because it was also used to
> make masks (or matts) for motion picture special effects and
> titles. It can be processed in any fairly active developer like
> paper developer or D-19.
>
> On 10/15/2021 12:38 PM, Martin magid wrote:
>> I developed a strip, and there is nothing printed on the edges.
>>
>> Now what?
>>
>> Marty
>
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
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