Does the resulting image appear to look like 1/4 F8 ISO80 rather than 1/120 F4 ISO 800 ?
Nope. i expected an overblown image and got a perfectly autoexposed one.
Upon further investigation i found the following:
- On half press the exposure shown on screen is the one i set to.
- In M mode i have the ISO set via canon's UI to 3200 and override via CHDK to 640, this results in an EXIF displaying ISO 200 (and the image exposure matches when i take the image with ISO 200 in canon's UI to check)
- - Testing with a handful of combinations of canon's UI ISO and CHDK ISO seems to suggest that the actual ISO gets locked at 200 regardless (in P mode it does the same but at 80, in Tv and Av auto iso kicks in)
- Shutter Speed and Aperture override doesn't appear to do anything other than change what the UI says on half press
- In video mode everything is auto
Hopefully this helps you out some