ISO vs TIME

[Phil-lost!]

Does anyone have any thoughts on whether its best to up the ISO and get twice as many subs or lower it and try for the maximum time your mount/light pollution will allow? I know the subs will be noisier with a higher ISO but maybe more subs stacked will more than make up for it? As you all know, the clouds usually roll in about 10 mins after getting set up so the more I can get out of a session the better!

[gnomus]

11 minutes ago, Phil-lost! said:

.....I know the subs will be noisier with a higher ISO but maybe more subs stacked will more than make up for it? .....

I used to think that too, but I am not so sure now.  At the end of the day you are trying to get a count of the number of photons that are hitting each of the pixels on your camera sensor.  That is going to be unaffected by what ISO you set your camera to.  

[wxsatuser]

As long as you don't reduce the overall imaging time,  it's total exposure that counts.

Example.......10 x 2minutes @ ISO 800 = 20 X 1minute @ ISO 1600

[Phil-lost!]

Thanks all, I might try to test both next time I get a chance. 

[dph1nm]

22 hours ago, Phil-lost! said:

I know the subs will be noisier with a higher ISO but maybe more subs stacked will more than make up for it?

In terms of electrons (or photons) higher ISOs are not noisier, so you do not need more subs. What matters is simply the total exposure time.

NigelM