There is another clue in the log file where the Sv value is reported as "hi" rather than a numeric value.
It looks like the script is working exactly as intended. I downloaded a copy of the script to my mobile and checked it carefully. Read on ...
The word "hi" in the script log is just the script reporting that the value returned by the camera is over ISO3200. However, the script uses the actual value it receives from the camera firmware correctly - the "hi" only shows up in the log text. So there is no problem there.
So I looked at how the script is adjusting the exposure values. This shot :
2018Jul13 00:00:16.080 1) IMG_0402.JPG
2018Jul13 00:00:18 meter : Tv:1/1250 Av:3.5 Sv:hi -1164:-1164
2018Jul13 00:00:18 actual: Tv:1/1000 Av:1.8 Sv:1600 Temp:27
2018Jul13 00:00:18 AvMin:1.8 NDF:NDout foc:infinity
tells me that the camera wants a shutter speed of 1/1250 of a second, with the f-stop at f3.5 and the ISO at 6400 (i.e. hi).
Using those values as a starting point, the script adjusts the ISO down to 1600 (
your maximum ISO2 setting), thereby lowering the exposure a factor of 4x. To compensate, it
adjusts the f-stop by 2 full stops from 3.5 to f1.8 (
your Av min) for a 2x increase in exposure. It also changes the shutter speed by 1/250 to 1/1000 (
your Tv min) for a 1.25x increase in exposure. As a result, the final image will be underexposed by about a factor of 0.75x
because of the limits you set in your script parameters! To fix that, allow a lower shutter speed (
Tv min).
A higher
ISO2 max would work but the script currently artificially limits the max ISO to 1600. I'll fix that in the next release.
I don't know why your LCD shows ISO1000 but, as per reyalp's comment and hundreds of posts on this forum, you can't go by what you see on your LCD (or sometimes even the EXIF values in the image). I have a suspicion that you have the ISO set to 1000 in the Canon firmware rather than ISO AUTO? That can cause problems too by the way - leave it in AUTO.
CHDK overrides are a hack - they bypass the camera firmware and sometimes that means the EXIF values or LCD display values don't match what was actually used to take the shot. Whether it does or not seems to depend on the camera and shooting mode and is a function of how the port was done. You have to examine the actual image to figure that out.
In the winters here, it gets very dark even at daytime.
You have my sympathy.
