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Posted by Richard Crowley on 01/22/08 01:39
"peter" wrote...
> On the canon xh a1 there is a 3-position gain selector switch that the
> user can pre-assign three different gain levels using the menu. Why do we
> need this? A more direct method is to have a dial like the XL1 or XL2 to
> cycle through all available gain values. This avoids using the menu and is
> very quick to adjust.
>
> The 3 position selector makes it difficult to shoot in this scenerio:
>
> When shooting stage performances in a theater, my main concern is to
> minimize low light noise. To do this, the obvious way is to set the
> aperture to wide open and shutter to slowest possible speed without motion
> blur, and then vary the gain as the lighting changes to maintain correct
> exposure. If the light level becomes so strong that even -3db causes
> overexposure, then and only then I close down the aperture or use a faster
> shutter speed. Based on previous experience with a different camera, this
> is not likely to happen -- I always had to boost gain quit a bit.
>
> But with a 3-position gain selector, it is not possible to do this, unless
> the theater happens to have only 3 different lighting levels. Leaving the
> AGC on is not an option either, because the stage is so much brighter than
> the surrounding due to spot lights and all, the AGC is bound to overexpose
> the subject, especially when zoom out to wide.
You may be trying to use the camera for a difficult application beyond
its design envelope. My Sony DSR-300 has exceptionally good low-
light performance, and like similar cameras you can use it with a CCU
or a "paint box" which provides continuous control of video gain and
pedestal, and some amount of red and blue "painting" adjustment, too.
(Along with the 3-position gain switch: 0, +9 and +18dB, in addition
to the +30dB setting for shooting in moonlight, etc.)
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