How do you know how many megabytes are in seconds and minutes in video clips on digital cameras?
ffdude13 asked:
On the movie/video function on digital cameras, how can you know how many megabytes it takes for each minute or second of video recorded?

the following may answer your question
howstuffworks.com
All camera brands are different. Some highly compress their video which means you can fit more movie on your card. The only downside is the quality will not be as good as one which is not as highly compressed.
If you add more information to your question (camera make and model), then I can tell you exactly.
Also, have a look at your user manual. It should tell you how many minutes of video you can fit on a 512MB, 1GB card etc.
it shows on the screen