What is Gain Control?

chuckinsocal

I was just browsing through my EXIF data in Bridge on a shoot I did the other night and ran across an item called Gain Control. Sometimes it is at 1, sometimes at 0. I've looked all through my camera menus and the manual but I see no reference to Gain Control.

I was shooting RAW with my D80 in Aperture priority, aperture set at 4.0 or the largest aperture the camera could shoot at a given focal length. The camera most often chose a shutter speed of 1/60. I manually set ISO to 400.

So, what is this Gain Control and how does the camera choose it? Is it something I can set my self?

I also notice that the Contrast varies from 0 to 1. I didn't think the camera would care about contrast while shooting RAW.

Probably a dumb question but my curiosity is killing me :dunno.

Thanks.

ziggy53

According to the organization that sets the EXIF standards (and using the EXIF 2.2 standards), the name "Gain Control" is also the field name "GainControl" and it is a "Rational" data type of "1" count (I presume 1 digit in length).

Additionally, "This tag indicates the degree of overall image gain adjustment."

... and,

"1 = Low gain up
2 = High gain up
3 = Low gain down
4 = High gain down
Other = reserved"

While I believe that each manufacturer is free to populate the field as they see fit, I am not sure what Nikon uses the field for and what camera settings might impact the field.

I continue to research however.

Excerpts taken from:

http://exif.org/Exif2-2.PDF

insanefred

It's a conspiracy! A conspiracy I tell you!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1

chuckinsocal

I was thinking that it had to do with sensor sensitivity or the sensor's power output to a file. Upon looking further, it seems that a Gain Control of 1 only occurs on some shots during night shoots with a flash (Vivitar DF400MZ). So maybe it has to do with controlling the power output of the flash? But, that doesn't seem consistent with "degree of overall image gain adjustment".

I've been unable to find anything on the web that defines "image gain adjustment".
My photos turn out fine so this is not a big deal. It's just a curiosity and thinks for looking into it.

SoCalAl

I believe "gain" is a reference to ISO. Can't remember wher I ran across that tho. Try a search for "dslr gain control".

NeilL

Some Nikon cameras have the option of shooting multiple exposures. If you do multiple exposures you have the choice of gain on or off. With gain selected, the exposure value of each of the images in the stack is adjusted to ensure the exposure of the final composite image is correct.

Neil