hi everyone,
when taking a night photo, how do you decide which shutter speed you should choose?
when do you use a shutter speed of only 10 sec. compared to a shutter speed of a few minutes? thanks. :)

Well, that depends on how much light you have,what aperture you're using, and what you're trying to do. The darker it is, the longer you will need to open the shutter for. The camera meter should give you an idea of how long to open the shuter for, but for longer shots, it can be a trial and error thing. For example, my cameras slowes shutterspeed it 30 seconds. If I want to go longer than that, I have to figure it out by trial and error. It's pretty easy to do with digital since you can see if the speed you chose worked for what you wanted or not. If you're shooting digital, don't be afraid to experiment. If shooting film, don't be afraid to experiment.

Exposure at night works just like exposure during the day, except if you're using film. Since there's so much less light out at night, you'll need more exposures which you can accomplish with a higher ISO setting (or faster film), longer shutter speeds and wider apertures. Adjusting only one of these from the settings you're used to seeing during daylight will only get you so far, so it's likely that you'll need really long shutter speeds and a high ISO setting. I usually keep my aperture around f4 or f5.6 in general for night shots - two stops faster isn't going to stop any action or anything if you're at a 30 second exposure...

Here's why it's different with film: Reciprocity Failure. Basically, once your shutter speeds get to a certain length the film doesn't react quite the same to exposure anymore. Longer shutter speeds need even more exposure. How much to use, and at what shutter speed you need to start adding it depends on the film itself.

thanks for the helpful info. :)

PG,

One thing to keep in mind is that there are no "right" settings for any situation. You have to think about what you want the image to look like, and set the settings to meet that vision, not the other way around.