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Hello! I just completed my tests with 4x5 TMax 400
sheet film. Using a Kodak gray scale, I used a 5000K fluorescent bulb and
exposed the gray scale at 1/10 sec at f4.7 for the normal exposure. Then,
I exposed at f4.7 at 16min 40sec using a 10,000 ND filter to estimate the
reciprocity failure. In order to eliminate the development variability, I
developed each set of pre-flashed negatives together with a normal exposure and
a unhypered exposure using the ND10,000 filter – so I developed 6
negatives at a time. I was then sure that I could compare each preflash
hypered negative to a normal exposure and an unhyperred exposure that had been
developed in exactly the same way. I used two techniques of preflash
hypersensitization. For the first technique, I used my camera flash with
a milk plastic diffusing screen over the lens for my 4x5 camera. I
calculated the distance from the film plane to a gray surface required to give
a normal exposure, then I calculated the distance to give N-3, N-4, N-5, N-6
preflash hypersensitization. For the second type, I metered the bright
blue sky, used a milk plastic diffusion filter, and shot N-3, N-4, N-5, and N-6
preflash exposures. I then used each preflashed negagive to exposure
the Kodak Gray scale using a 10,000 ND filter at f4.7 at 16min 40 seconds. I had the negatives scanned at the local
photo shop with instructions to scan the negatives at the same settings and to
scan without any “improvements.” TMax had consistently about 1 2/3 stop
speed loss after 16min 40 seconds in the two batches. No preflashed hypersensitized negative
had improved speed compared to the negative that had not been preflashed.
In fact, each preflash negative appeared to have worse reciprocity failure than
the unflashed negative; the most pronounced effects seen with the negatives
that had the most preflash! Preflash hypersensitization does not
appear to improve the reciprocity failure characteristics of TMax 400 sheet
film. Best regards. Mike --- |
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