Start with your cameras manual. It may help you to understand terms and relationships between functions. I have a Canon XH-A1 and have read the manual numerous times.

Terms like gain (ASA in the film world), iris, shutter speed, etc. are (for the most part) derived from the film world and are applicable to the video world.
Pick up a book on the technical details of still cameras or search the net and I'm sure you'll find several tutorials that will help explain these terms to you.

Mike

Or perhaps you want to know more about how they interact with one another i.e. why one might change shutter speed rather than aperture?

You are right Bob, would like to know more about this.

I know it's much about practise and testing too.

Thanks.

/Ulf

Mark's advice is pretty much on the ball.
There's also books from the ASC but they might be more information than you really want.

It really comes down to the following:

Aperture, shutter speed and gain can all be adjusted to obtain correct exposure. You can change anyone of those and offset that by changing anyone of the other two and still get the correct exposure. The reasons why you might make the choice of one over the other is because of the secondary effect and how that affects the look and feel of the image. Once you understand the 'what each one does' it really does come down to a creative choice and practice and testing as you said.

Gain: As Mark said this is analogous to film speed (ASA). You usually cannot reduce this below "0" with a video camera. Secondary effect of increasing gain is more noise. Generally one increases gain as a last resort when there's not enough light. The same applies to film, higher ASA means larger grain.Grain is not the same as noise and is generally considered more visually acceptable than noise.

Shutter speed: For film and video the usual setting is half the frame rate. Secondary effect is if you make it any slower you may get more motion blur than is acceptable but this can be a valid creative decision. Make it any faster and you may get less motion blur than is acceptable but this can be a valid creative decision. The effect of changing shutter speed is most noticeable at lower frame rates and especially shooting progressive at 24fps.

Aperture: Opening and closing the iris directly controls the amount of light going through the lens. Secondary effect, it also changes the depth of field. Tertiary effect, all but the most uber expensive lenses tend to have a 'sweet spot'.

As you can see the iris is the first thing one generally adjusts to get the correct exposure. Adjusting the other two produces possibly undesirable secondary effects but one may change shutter speed as a quite valid creative decision. It's hard to justify increasing gain for creative reasons as noise is plain ugly so this is more something done when the iris is fully open and you cannot add more light to the scene.

There is another way to control the amount of light, neutral density filters. More expensive cameras have two or three built into the camera and you can add your own in front of the lens. This is a pretty common solution when you don't want to increase shutter speed and you want to keep the iris wide open to keep the depth of field shallow.

I think that's pretty much it, if not hopefully others will chime in. I hope I've been of some help and not gotten anything technically wrong. In my opinion saying anything more leads into interminable, heated and largely pointless discussion about creative choices. That's something you should form you own opinions about although many will say that's just Bob's opinion and what they have to say is absolute gospel :)

Bob.

[edit] My comment about Shutter Speed is wrong / confusing!
It's perhaps more accurate to say "double the frame rate" e.g. at 30fps the usual 180deg shutter opening is 1 /60th of a second.
At 25fps it's 1/50th of a second.

Thanks to David McKnight for pointing this out to me.

You pretty much nailed it right on the head Bob, and let me say thank you for taking the time to do so. This is information I'm certainly capable of conveying, but so many times, I either don't have the time, or I just sit and think, man - that's going to take a lot of writing to answer, and I would rather not have to do all that writing :).

So - I'd say Bob hit it pretty much right on, and I sure appreciate him doing the work for the rest of us that knew, but were too lazy / busy to answer.

Dave

This is awesome Bob - Thank you very much for your time writing all this good stuff.

This again proves the fantastic value of this forum! :-)

/Ulf

Some other resources for you

Camera Command DVD

Bare Bones Camera Course for Film and Video

If you do any type of wedding work at all, Mark and Trisha Von Lanken's DVDs on Moving Camera Techniques are invaluable:

Mark and Trisha Von Lanken

Good luck, and I hope this helps

- David

<edit> link-ified the...links

Great David - Thanks a million too. :-)

/Ulf

Hi

Maybe someone else can benifit from this page:

http://www.mediacollege.com/video/

/Ulf