Figuring long exposures

[Nu2this]

Hello everyone, been looking for a while but really haven't posted before. My question is about long exposures, 10, 20, 30 seconds or more. How are these figured? I've read comments on some threads like "30 seconds was all I could go without blowing out the sky" or "I tried to expose long enough to get good detail in the <subject> while still leaving the shadow areas dark enough". How are they figuring ahead of time what they need? I am somewhat new to photograpy in that I do well at what I shoot (mostly landscapes) but am very limited on just about everything else. I would like to expand my capabilities as much as possible and can figure out a lot of other types of photography but I have no clue on this one, HELP PLEASE!!!

[olly_k]

I am somewhat new to photograpy in that I do well at what I shoot (mostly landscapes) but am very limited on just about everything else.

I think you have answered your own question! It takes practice and time to be able to judge light conditions and set an exposure accordingly and I bet even then there is some +/- error with the greatest of pros.

Just mess around and note your settings, then learn from that.

[eddarr]

Exposure is figured the same whether it is 1/250 or 20 seconds. The camera meters the subject and gives you a suggestion. You then decide if you agree with the camera or make adjustments.

However the camera will only provide suggestions up to 30 seconds. After that you are on your own. The easiest way is to let the camera figure it out based on 10, 20 or 30 seconds of exposure. Say the camera is telling you it should be 20 seconds at f/5.6 but you really want to use f/8.0. You are adding one stop of aperture so you must add one stop of shutter speed by decreasing the SS to 40 seconds.