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Turning the electronic "iris" up and down is like turning the gain up on any other pick up deivice, say a microphone for example. These CCD chips are optimized for a certain light level and that would be 0 db. Any more gain than that and the CCD strains to see more light, brightens the scene, but at the same time begins to introduce video 'noise' into the picture. Any less than 0 db and the picture simply gets darker. [the -3dB setting may give you even less noise than 0 dB. jpb] For most video applications you can use the AUTO everything function. However, the constant opening and closing of the auto iris can be annoying and if it opens too high in lower light situations you would get a "noisy" screen. If you have a subject that has a bright background - the iris would close down so much as to turn you subject black. So the next simple thing to do would be push the "exposure" button and select a stationary level that suits your lighting condions. The best I can tell, the trv-900, when in the "exposure" mode, lets the aperture close down to darken the picture and holds the electronic iris at a 0 db or -3db level (which is selectable in the menu). For brightening the picture, the aperture opens all the way and then begins to raise the gain of the electronics.

The SHUTTER speed setting, normally used in still photography, can also be useful in video taping. Normally it is set at 1/60 of a second. If you plan on taking some stills (freeze frames) from the video you can set the shutter to a faster setting, say 125, and the stills will look better. For very low light settings you can slow the shutter all the way down to 1/4 of a second. Now this will hold the "shutter" open for a long time to let in the maximum amount of light. But it will also give a strobed effect on the video - simply because the shutter is opening and closing very slowly. In other words, its taking a separtate picture only ever quarter of a second. This, by the way, is how the "candelight" pre-set is configured. For a neat "motion picture" effect you can set the shutter to 30. [video camera shutters are electronic gates on the CCD- no moving parts- but the effect is like a mechanical shutter in a film camera. jpb]

The F/stops are just a reference to the diameter of the opening of the aperture and how much light that "hole" will let in. In still photography the f/stop setting not only affects the brightness of the photo, but the depth of field as well. Depth of field is that part for scene that will be in focus. For some reason, when the aperture is sqeezed down to just a pin hole, the focus range is great. When the aperture is open wide - the opposite occurs and the focus range narrows. This must be much like "sqinting" for the human eye.

There is a lot to still photography. And the trv-900 does an excellent job as a digital still camera. As a video camera - the 900 does equally as well - but you can get along pretty well with just "auto" or "exposure" mode for most situations. Ok, it took me a good day of playing with this thing to come up with this. If there are any errors please correct me.
Tony Perry <perry@multipro.com>
crossville, tn USA - Saturday, August 14, 1999 at 23:27:33 (PDT)

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