Setting The Gain Or Iso - Sony PXW-FS7 Quick Reference Manual

D. Preparing the camera and shooting
D3. Setting the Gain or ISO (Custom Mode)
The signal that comes from the cameras sensor can be
made brighter by adding additional amplification by
increasing the gain of the cameras image processors.
This may be useful when shooting in low light situations.
However it should be noted that when you increase the
camera's gain, as well as making the desirable image
brighter you will also increase the noise seen in the image.
Because of this it is normally desirable to use the lowest
possible amount of gain for the best results.
The gain setting of the camera can be displayed as "gain"
in dB or as the equivalent ISO rating of the camera.
D3.1 dB gain is easy to understand. 0dB is no added gain
and the optimum setting for the best possible image
quality. Every time you increase the gain by 6dB you are
making the picture twice as bright (equivalent of opening
the lens aperture by 1 stop). But adding 6dB of gain also
increases the noise in the image by a factor of 2. Adding
+6dB gain makes the picture twice as bright but 2 time
noisier, adding +12dB will mean a picture 4 times brighter
than 0dB but also 4 times noisier and so on.
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