Develop at 0.6 gamma...what does that mean?

[Daniel D. Teoli Jr.]

When the lab is instructed to develop at 0.6 gamma what does that mean?

Are they saying the film is overexposed by 40% and the lab is to develop at 60% of the normal time?

There was a note to the film lab by Robby Muller in the film 'Down By Law' that mentioned this in the special features.

Edited February 8, 2020 by Daniel D. Teoli Jr.

[Simon Wyss]

No, no. Gamma is a trigonomy term, it is used to express the angle between abscissa and central straight part of the characteristic density curve of a photographic material or in other words the steepness of it. Abscissa of a graph plot.

Gamma 1.0 means the 45 degrees angle. Density, by the way, is laid down in logarithms, amounts of light as well. Gamma 0.6 designates a softer grey scale, less contrast. Gamma 2.3 would belong to a harsh image. This is densitometry and in my eyes not so very darn important to the cinematographer. When Robby Müller asked for 0.6 he could have said I want the negative just a tad softer. Motion-picture film negatives are generally developed to a gamma of 0.65.

[Daniel D. Teoli Jr.]

for...just a tad softer.

Does developing at a different gamma require a change in chemistry or development time?

[Simon Wyss]

That is a bright question.

A time-gamma curve is plotted for a given developer. If you want to retain a film’s maximum density and develop it softer, you have to change a few things. Luckily there are formulae that bring out Dmax at lower contrast and varying times.

Example, see page 2