What are exposures?

[shayrgob]

If someone says that you need exposures of 30 seconds. what does that mean?

 

[LittleMan]

That would mean that you are 'exposing' the film to the light for 30 seconds.
How you expose the film is the shutter speed which is how long the shutter is open, that is what you would change to set it to 30 seconds.

Of course, 30 seconds is a very long time for it to be opened. So the photo would be 'over exposed' (too bright) unless you are in a very low-light situation.

There is a lot more to it and I'm sure someone will answer you in more detail.

 

[Meysha]

A normal photo usually has one exposure. That means that you open and close the shutter once, letting a certain amount of light hit the film/sensor.
This is called the shutter speed. If you have a slow shutter speed you have a long exposure.

When they say a 30 second exposure... they're just saying that you leave the shutter open for 30 seconds. It must be a very dark environment for the exposure to be that long otherwise you'll end up with big white splotches or a completely white screen/frame if it's the scene wasn't dark enough.

 

[LittleMan]

Just barely beat you to it Meysha.

 

[shayrgob]

How long does the shutter stay open w/ normal photographs?

 

[PlasticSpanner]

It would depend on what you were photgraphing & other settings on your camera but exposure times between 1/60th second and 1/500th second are about normal.

 

[Unimaxium]

Here's a good-looking web page with beginner information on shutter speeds. This should help you understand better how the shutter helps control the exposure of the film. And here's a webpage with info on the aperture, the other part of the camera that controls the exposure. And this page better explains how the two relate and form the exposure.

 

[doenoe]

thanks for those links
greetz Daan