On perhaps a slightly different topic:
I was thinking of using rawoptint to photograph a sunset/moonrise on a nice white mountain. It would just be important here that the interval is kept close to 15s, the ISO at 200. With that I could take well exposed single shot with the shutter speed going from about 1/1000 s in daylight to 15 s in moonlight, if my calculations are correct.
What parameters would I have to set to what values for this to work?
Max Tv Sec/1000 = 15000 (or less to allow for image saving while keeping 15s exactly, perhaps 14000 for jpeg, or 11000 for raw, depending on cam)
Min Tv Sec/100K = 100 for 1/1000th
Target ISO = minimum your camera supports in the Canon UI (usually 80 or 100)
ISO adj TV Sec/1000 = the value you used for Max Tv Sec/1000 (if you want ISO to only adjust once the longest shutter speed is reach) or less (if you want ISO and shutter to adjust together)
Max ISO = 200
Of course, if the moon will be in the scene, you won't be able to expose it and the mountain correctly, so you need to decide which to prioritize.
Some relevant settings
"Overexp thresh x/100k"
Controls how much of the scene is allowed to be over exposed. If it's larger than the fraction of pixels the moon takes up, then the moon will be over-exposed, and the scene will be more correctly exposed. The fraction depends on zoom. You can calculate from the FOV and knowing the moon is ~1/2 degree, but if you aren't using a lot of zoom, a few percent (values of a few thousand) should be plenty to ignore it. If you do want to properly expose the moon, I suggest calculating the actual fraction. If the fraction is very small, you may need to reduce "Histogram step"
"Underexp thresh x/100k"
Controls how much of the scene is allowed to be under-exposed. This will resist the effect of the overexposure protection. Generally it should be a larger fraction for over-exposure. Higher values allow over-exposure protection to have more effect. If you want to allow the moon to over expose, the default of 10% should be OK, but if you want to minimize how much of the scene gets blown out, you can use a higher value.
"Underexp -Ev"
How many stops below correct exposure the scene can be before it counts as under exposed. Larger values will allow the scene to get darker when there's over exposure in the scene.
"Meter low thresh -Ev" and "Meter low limit Ev"
Work similarly to the previous items, but for the average value of the scene, rather than a fraction of pixels. The "thresh" value controls what exposure value it starts to take effect (resisting further exposure change from bright objects) and "limit" sets where it reaches full effect. Again, if you want bright objects to allow the scent to get dark, use larger values. If you want to keep the scene well exposed at the expense of having bright areas over-exposed, use lower.
FWIW, I've been meaning to put out a new release of this script for a while, but for various reasons haven't quite got around to it. The in development version is at
https://github.com/reyalpchdk/chdkscripts (use "download" next to "development build" for the latest)
Some bugs that caused flickering in certain situations are fixed. New bugs are also undoubtedly introduced, but identifying them is left as an exercise
