or
(a
0
For normal colour films, Colour Balance is taken as the differ-
ences in log exposure of the red and green H & D curves from the blue
curve at a density of 1.00.
For infrared colour films (i.e., 2443), Colour Balance is defined
as the displacement of the red H & D curve relative to the intersection
of the green and blue curves, regardless of the intersection point
density.
3.2 RESULTS
Extreme heat exposures caused vaporization of a base component for
most films tested, characterized by a distinct odour. This was accom-
panied by tight curling and brittleness, especially for the 2445 and
2424 materials.
Film speeds and average gradients were found to follow a definite
trend, typified by type 2445 (figs. 1 and 2). For light-exposures
before heating, film speeds ''peaked", i.e., increased above the control
("0 hrs-heated") speeds, dropping as heat exposure was extended.
Further heating caused emulsion softening and sticking, and occasion-
ally stripping during processing. Similar peaks were observed in the
gradient vs. heating time curves for the monochrome films (fig. 3). It
is suggested that all films exhibit speed and gradient maxima for light
exposure before heating; these may occur below room temperature for
some emulsions, as reported by Henson?. Light exposure after heating
usually resulted in a continuous decline in both film speed and
gradient. However, it should be noted that type 2448 film displayed
a reversal.of the "before" and "after" variations.
Fog level generally increased (decreased, for reversal films) with
heat exposure, though as with the other properties the magnitude of
this effect depended on film type (fig. 4). Substantial changes were
observed for all but the 2402 and 2405 emulsions.
Colour Balance shifted with heating for the three colour films
examined. 2443 showed the least effect while 2445 was considerably
shifted to a green colour for light exposure after heating and shifted
to a blue colour for light exposure before heating (figs. 5 and 6).
Only one of the six films departed from these general trends.
Type 2405 (Double-X) exhibited a temperature-dependent 'bump' near the
base of its H § D curves (figs. 7 and 8). The effect is prominent at
70°C, less pronounced at 60°C, and completely absent for 50°C heat
treatment.
3.3 CONCLUSIONS
A complete presentation of variations in properties for each of
the films would be inappropriate here, and of limited usefulness to the
