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I think that the Philips webcam has a 640x480 chip, so I’d use the settings for 640x480, which means that the imaging region of the chip is an area 640 pixels wide by 480 pixels high.
An all-white display normally would indicate a gross over exposure; all the pixels are saturated and are registering a value of 255 which is pure white, with 0 being black on an 8-bit scale.
On warm evenings most un-modified webcams will show noise when exposing for longer than say, 1 or 2 seconds. The way around this is to cool the chip. For example, my SBIG ST7 CCD camera can be cooled to around 30 degrees below ambient temperature and for each 5 or 6 degrees temperature drop, you roughly halve the noise.
Unfortunately, with a standard webcam you will see noise, especially on those warm Brisbane nights!
Cheers
Dennis
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