rawopint needs tweaking I guess?
It shouldn't make much difference, you can probably use a higher ISO for the same quality.
What would be the reasonable settings for underexposure and overexposure control if we would do a timelapse run from dusk until dawn?
Priority would be the stars, milkyway andsuch, so a whiteout of the moon is not a big issue.
If you want to ignore the moon, and have underexposure protection disabled, then your Overexp thresh should be larger than the moon. To calculate this
- Get your field of view. You can use this Angular Field of View Calculator with focal length in 35mm equivalent, multiplier 1 (or use actual FL and multiplier for your cam), 4:3 aspect
- Moon is about 1/2 degree, so Moon width in pixels = 0.5*(sensor width in pixels)/(horizontal fov).
- Moon pixel area roughly = width squared (yeah, I know it's round
) - Moon pixel area in parts per 100k = (moon area)*100,000/(sensor area)
Your Overexp thresh should be larger than the value in #4. Note that overexposure protection has some effect before the threshhold.
The sun is about the same angular size, but it's so bright it will blow out a larger area and so will still trigger over-exposure protection to some extent. Both the sun and moon can overexpose a much larger area if there is some cloud.
The same calculation is useful if you want to correctly expose the moon. In this case, your Overexp thresh needs to be smaller than the value in #4, and your histogram step must be significantly smaller than the value in #2. You also need to make sure meter low limit doesn't counteract over exposure protection, by using prio or weight adjustments.
If you have under exposure protection enabled, it will limit how far the exposure can be shifted by over exposure protection, so for a night scene that is mostly black, the effect of over-exposure will be limited no matter what the Overexp thresh is.
For the sx260 underexposure control is turned off, is that OK for such a dusk -> dawn run?
Underexposure protection essentially varies how hard the script tries to resist exposure changes in the opposite direction. So if you aren't worried about correctly exposing the moon, it won't have much effect at night. It will change the behavior at sunset and sunrise, by allowing more over exposure to keep the darker parts of the scene more visible. Whether this is desirable is a matter of preference.
We'd like to have the sensitivity and exposure to go up as soon as possible when it gets dark....
With default settings, rawopint will try to keep the exposure at the target value until it hits the exposure limits. This actually looks quite strange in a sunset, because the color changes but the scene stays the same brightness and then drops very quickly when the limit is hit. I highly recommend using Bv Ev shift to get a more natural effect. This will lower the target exposure at night, but this doesn't really matter because the script will be on the limits once it gets really dark.
No matter what, I would recommend making some sunset or sunrise tests.
