Gamma mesure

Discussion in 'Enlarging' started by Inclanfunk, Aug 28, 2007.

  1. Inclanfunk

    Inclanfunk Member

    Aug 25, 2007
    Paris, Franc
    Medium Format

    I would like to dig into contrast masking and I am stunk into the densitometer part.

    As far as I understound the process the mask could be low contrast, average, high, etc. depending of the exposure/time developing.
    Here is my wondering:

    How can I mesure the gamma to know if I produced a .1, .3, .6 gamma mask?

    In other words how a densitometer is working to mesure the gamma of the mask?

    Is the density mesured by projecting on the easel or straight from the mask (if so how?)?

    Is there another (even less precise) way to determine the gamma of the produced mask?

    Thanks for your precious advices,

  2. Donald Miller

    Donald Miller Member

    Dec 21, 2002
    Large Format
    The measurement of the gamma of a contrast mask is usually expressed in terms of the peak density of the mask. (This is true in my experience...however there may be other expressions of the value).

    The densitiometer is used in the transmission mode and the measurement is done on the region of highest density of the mask. The density is measured through the mask itself with the densitometer.

    The less precise way would be to visually compare your mask peak density to a known density such as a neutral density filter.

    I hope that this is of help...masking, while labor intensive, is a repeatable way to accomplish contrast reduction, enhancement, or sharpening of the print in singularly predictable ways.