I tried it and worked very nicely! Anyway, another suggestion I want to post is that if the image is too bright or you simply want to make the image darker w/o noise, when you bring the images into your edit suite, you can do so there.
The only editing program I know to use is Final Cut Pro 3 (Yes, I know we're upto 5!). When those images you want to darken are in the TIMELINE, you can DOUBLE CLICK to put them in the VIEWER > CONTROL - SINGLE CLICK in the VIEWER > COMPOSITE MODE > SUBTRACT. Presto! Darkened images.
Before doing this you can also use ADOBE PHOTOSHOP CS, BATCH CAPTURE intended images, CURVES > and adjust the curve of the image(s) there. This is a fine tune method where you have more control than what is up above.
If you don't have Adobe PS, then, your only alternative is using the composite mode in FCP. Good luck to all.

Melvin Delvecchio - Bronx Cinematographer