How does turning off part of the camera during long exposures benefit the final image?
In order to collect all of this light, we slow the exposure time so it takes many seconds or even minutes. If allowed to glow, this little ember in the upper left corner would fill that part of the picture with a visible and very undesirable feature we call amplifier glow. Now this naughty little amplifier is not really needed while we are collecting the light because it is only used after the exposure is taken to read out the image. So rather than feed it power (and heat) during the exposure, we drop the main voltage to a point at which it effectively turns off, thereby greatly diminishing the amplifier glow. Now you might think to yourselves that this is a pretty clever little trick but to our seasoned camera designers we would no more think to leave this little amplifier running than to leave our car idling in the parking lot all day while we work inside.
