Hello! I wanted to try some
Maco Cube 400 35mm film since it is panchromatic and its sensitivity extends
to 720 nm. I used my Kodak gray scale under a 5000K fluorescent bulb and
obtained normal exposures at 1/8 second at f4. I then used my ND 10,000
filter and exposed the gray scale at f4 for 20min 50sec. I developed the
film to an ISO of 400 according the manufacturer’s recommendations using
SuperGrain developer. The film appears to have about 2 2/3 stop loss
over this exposure period.
For interest
sake, I then repeated this test using my Lumicon H-alpha filter. I
obtained a normal exposure at 1/8 second at f1.8. I exposed the gray
scale for 20min 50 sec using the 10,000 ND filter over the H-alpha filter at
f1.8 and developed the negatives to an ISO of 6400 in accordance with the
manufacturer’s recommendations. The film again appeared to have a 2 2/3
stop loss over this time using the H-alpha
filter.
The film is
sensitive the H-alpha, but has a speed stop loss equivalent to llford
SX-200. If this film can be pushed to such a high level then the 2 2/3
stop loss may be inconsequential if the grain is
tolerable.
Given the
upcoming demise of Tech Pan, one possible use of this film would be to use 4x5
TMax film (or other H-alpha insensitive B+W film) to obtain tri-color
negatives (or to use color slides or negatives for the color work) and use a
sheet of Maco Cube developed at 6400 for the H-alpha channel. 35mm film
may be able to be used instead of the sheet film since the grain might not be
noticeable in the final processed print since the grain would be isolated to
only the H-alpha channel. However, 4x5 sheet film developed at 6400
might have minimal grain in any case.
Best
regards.
Mike