[APML] TechPan Hypering Experiments

[Aplanatic@aol.com]

Hi List,

A couple of months ago I built a densitometer and exposure box in order to do 
some experiments on hypering TP 4415 (4X5 sheets).  After about 6 weeks of 
darkroom work here are the results so far:

In each case the film was hypered using a Lumicon 1200 chamber at 49 C.  I 
strictly followed the hypering directions supplied by Lumicon.  The chamber 
was pumped down by hand and filled to +3 PSI after coming to temperature.  
This cycle was repeated a total of three times.  Forming gas, as supplied by 
Lumicon, was used.

The film was exposed using a green LED through 3 layers of white diffuser, 
the last diffusing panel being 12" above the film.  Each film sheet was cut 
into four strips after hypering so that various experiments could be 
performed.  A Stouffer step density wedge was placed in contact with the film 
during exposure.

The densitometer is a simple device consisting of a green LED and a 
phototransistor mounted facing each other across a 15 mil gap.  Both the LED 
and phototransistor are mounted in holes in black plastic.  Both devices look 
through 0.1" diameter openings in order to control the region of film being 
sampled.  The current through the phototransistor was measured to determine 
the film's density.  The densitometer was tested for linearity by using 
various combinations of Wratten neutral density filters, and shows a usable 
dynamic range of 10,000 (4.0D).  Linearity and accuracy are better than 0.05D 
over a range of 0D to 3.5D.  The Stouffer step wedge was then calibrated 
using the densitometer.  Interestingly, the step wedge shows a maximum 
deviation of about 0.15D from the ideal result of 0.2D per step.

The first set of experiments explored the effect of various hypering times 
and development times.  D-19 was used in all cases, as was very fresh film 
(08/2002 expiration).  In each case the film was exposed for 8 minutes 
through the step wedge, and developed at 68 degrees F using constant, gentle 
agitation.  A 30 second pure water stop was used, followed by 5 minutes of 
Kodak fix.

Compared with a sample of unhypered film, here are the speed increases for 
various hypering times where the film was developed for 8 minutes.  Speed 
increase was measured at 0.3D above base+hyper fog density.

Hypering Time..............Speed Increase..........Base+Fog

0 hours (control).................1X.........................0.085D
24 hours.........................7.5X.........................0.13D
48 hours.......................15.2X.........................0.17D
72 hours.......................20.4X.........................0.31D
96 hours.......................21.4X.........................0.45D

As a function of developing time, the film's speed dropped roughly 20% when 
developed for 6 minutes and increased about 12% when developed for 10 minutes 
(72 hour hyper results), but the effect is less pronounced for the longer 
hypering times, and more pronounced for shorter hyper times.  Hyper fog also 
increased slightly for longer development times.  More details on this are 
available if you are interested.

The next set of experiments determined the low intensity reciprocity failure 
(LIRF) of the film for various hypering times.  I exposed the film for 15 
seconds, 2 minutes, 8 minutes and 64 minutes and developed for 8 minutes in 
D-19.  The results were quite interesting.  The unhypered film showed a 1.2 
stop change in sensitivity from 15 seconds to 64 minutes, and film hypered 
for 72 hours showed no measurable difference, i.e., no LIRF within my ability 
to measure it.

Finally, I explored the effect of storage conditions on the film.  I hypered 
three sheets for 72 hours.  I then placed one sheet in an otherwise empty 
film box in a desk drawer for 10 days.  The second sheet of film was placed 
in another empty film box, double bagged and placed in the freezer for 10 
days and the third sheet was developed immediately after hypering.  Each 
sheet was cut in half and developed for either 8 or 10 minutes in D-19 
without being exposed.  The second and third sheets were very similar and 
uniform, but the first sheet showed a significant amount of mottling, and the 
mottling was definitely worse (visually) for the longer development time.  
This suggests that mottling is at least in part caused by exposure to 
humidity.  No surprise.

I would NOT recommend that anyone change their hypering procedure or 
development method based solely on the above.  However, from it I conclude 
that optimum conditions (for me) are 72 hours at 49 C, developed for 8 
minutes in D-19 at 68 F.  This set of conditions shows very good speed 
increase, low hyper fog density, and a bit less sensitivity to mottling (than 
the 10-minute development case).  Increasing the hyper time and/or 
development time above this does not yield any big advantage in film speed 
for this low vacuum hypering method.

Not too much new here, but the numbers are interesting and the experiments 
are fun to perform.

Dave Rowe











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