I want the taken pictures to get dark more slowly between something like bv200 to bv-300....for now limited to 1 sec, that could be 4sec, 2 stops further if the camera and I permit that.
If that works i would expect then that s going from night to day 1 sec exposure would still be used until it reaches bv-300 (approx) and that it would change back to the original calculations between 1 sec and 1/60.
since the original calculation Av+Tv=bv+sv results in a specific exposure my first thought was to change that formula so it would allow for a longer exposure.
sort of cheating the camera in thinking it
is darker(not true bv values stay the same) uses a lower ISO than it actually is thus moving the exposure to a longer shot earlyer than expected.
using a multiplier on the calculated exposure time at set timings before shoot would probably also do it.
after some tests I can do the other way around, so cheating the calculated exposure by using an available higher iso and so shifting 1sec exposure to bv-500 or even lower bv values (bv-768 or darker @ max 1/4sec exposure @ any ISO you set before you started)....but that is completely opposite to what i want. This way in the images it gets darker more quickly. (alas a lower iso is lost in the dark)
and, more importantly, for my purpose it is too much to change 1 stop or more during a shoot (1/3 stop iso values, like 250 and 320 didn't gave stable results in my tests, but maybe i should do more).
it creates a too big a shift in how the image is illuminated..the actual shift should be no more than 1/3 stop per exposure time (so f.i. 1/3 shift at exposure 1/60, 1/30 and at 1/10, creating 1 full stop difference between 1/60 and 1 sec.)
btw this doesn't help astrophotography since the camera is still bound to it's absolute maximum exposure/iso values
and if you are bothered with +1 on the left, i can always shift it to the right side as -1
