Perfect exposure time in Bulb mode
How do you calculate the right exposure time to shot in bulb mode?
I mean in order to shot in a dark environment, you can set the highest ISO and then,decreasing this value, increase time or aperture. But what if you reach 400ISO and 30sec of exposure. How can you go on increasing time? I mean, is 31,32...or 30,40sec or something else?!
Another thing that I can't understand is: if you are in complete dark, without lighting hints, how can you set your camera? Randomly and then step by step set it exactly?
Sorry if those are stupid questions, but I can't go on!
Thank you!!
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