I cleaned up the time lapse script yesterday, adding a few more options to the parameter list. One was the option to enter the minimum and maximum ISO. I was using sv96, but those are hard numbers to figure out, so I changed it to enter ISO, and convert with my new conversion routines.
In order to be able to enter "Market" ISO, I had to convert it to "Real" sv96.
By setting the camera to ISO 100 (market), and running a script that does:
get_sv96()
I discovered that 100 Market is 411 sv96. If you then do:
sv96_to_iso(411)
you get 65 ISO, which is the "Real" ISO.
If you convert 100 (real) ISO to sv96,
iso_to_sv96(100)
you get 470. This is 59 more than 411, which is the sv96 offset to use. So here's how I get "real" sv96 from the "market" ISO input
@param z ISO Max
@default z 800
@param s ISO Min
@default s 100
svdiff=59 -- real to market difference
svmin=iso_to_sv96(s)-svdiff
svmax=iso_to_sv96(z)-svdiff
To print out the Market ISO for each shot, I use:
sv96_to_iso(sv+svdiff)
I've got some rounding error problems in my iso conversion I need to work on. Entering ISO 800 ends up ISO 802 after being converted to sv96 and back. So I think I need a scale factor for ISO, i.e. ISO 8000 for ISO 800, or maybe ISO 800000.
The sky was relatively clear for a few hours at sunset last night, so I hauled 2 big tripods, a Gorillapod, 3 cameras, external batteries, extra warm clothes, water, headlamp, and a cheeseburger up to the top of Spencer's Butte. Unfortunately, the ribbon of clouds on the western horizon blocked the view of the comet. Fortunately, the clouds were really beautiful.
http://www.youtube.com/watch?v=uRio1KM-LuM#