RE: filmscanners: This Gamma Thing...?

["Laurie Solomon" <laurie@advancenet.net>]

I will take a shot at responding; but there are others on this list who can
probably give a much better answer to your question.

Generally speaking Gamma represents the midtone setting.

In digital cameras it represents the white light setting ( sort of like a
light meters 18% gray reference point); in monitors and scanners it
represents the midtone setting ( and more particularly, the midtown
grayscale setting midway between the uppermost highlight setting in a
historogram - 255 - and lowermost shadow setting in a historogram - 0)..  It
comes from the printing industry where it represents a way of taking into
account ink absorption and ink spread for a given type of paper and surface.
The greater the ink absorption and spread, the higher the gamma.

In the digital world, typical normal default settings for gamma run from 1.8
to 2.2. 1.8 gamma producing a lighter rendering  of the image and 2.2.
producing a darker rendering of the image.  I would suggest selecting either
1.8 or 2.2 as your gamma setting.

-----Original Message-----
From: owner-filmscanners@halftone.co.uk
[mailto:owner-filmscanners@halftone.co.uk]On Behalf Of Tom Christiansen
Sent: Friday, February 02, 2001 9:07 PM
To: filmscanners@halftone.co.uk
Subject: filmscanners: This Gamma Thing...?


Hi,

I've learned a new word today: Gamma.

It's something with the way monitors show images, but what exactly is it??
I notice that my scanner software has a gamma adjustment and playing with
it I noticed that it changes the way the image appear on the screen.

But what exactly is this mysterious gamma thing?

My scanner software defaults to gamma=1.4. It this an optimal value? If
not, what is a better value?


I'd appreciate some scientific facts about this gamma.


Thanks,

        Tom