Hello! I'm a semi-experienced user of CHDK, and I use it mainly for the long exposure features and the scripting capabilities. I recently had an issue with my SX110IS, so I took it to Fry's and they gave me an SX120IS to use in the meantime, while the 110 is sent into Canon. CHDK runs well on this model, but the sensor itself is very noisy during long exposure shots.
I've tried several things to help, such as enabling Dark Frame Subtraction, moving it away from *any* extraneous light source, and reducing the brightness of the LCD for my shots. All of these efforts don't seem to fix the large amount of extraneous light that the sensor detects on the long exposures. I've attached a picture so you can see what I'm referring to (this is a 203 second exposure, with dark frame subtraction on, 2.77 aperture, ISO 80, no EV correction).
My guess is that the backlight from the LCD is somehow getting into the sensor. So, my question: is there a way to turn off the LCD during an exposure? I've read about the flashlight mode, but is there any way to do the opposite?