For starters, I'm going to assume you are not shooting with a flash. I might discuss flash in later entries, but honestly, I'm not that good with it myself, and it's something I'm still trying to learn.
This is what I used to shoot Camp Hollywood this year, and I think this is a good starting point for an lit indoor venue (competition, as opposed to a darker social dance):
- Exposure 1/125 sec. Not too much blurring. Ideally, it would be faster, like 1/250 sec or better, but swing dances are usually pretty dark. Sometimes, I've gone down to 1/80 sec to lower the ISO.
For me 1/60 has a just little too much blur, though I've accidentally shot some contests that way (like the first 2 images on the right), though you can see the difference between 1/60 and 1/125 is subtle - compare the feet, and try to imagine how fast they're moving in each.
- F-stop f/4-f/5.6. Even if the lens can go lower, I usually will still shoot competitions at f/4. I've had issues with the focus, especially since all my subjects are constantly moving. f/2.8 is sweet when it works, blurring out the background, but is really unforgiving if autofocus picks the wrong thing to focus on(but really, try it for yourself).
- ISO 3200. The 5D mark 2 can go up to ISO 6400(not including special "H" modes). But with all cameras, as you get to the higher ISOs you start getting more noise. I like to back off a little bit from the top.
- White Balance 2500 deg K. Just stay away from "AWB" (Automatic White Balance). Camp Hollywood just has really warm light, and with the yellow walls and lampshades, the Color Temp is wayyy down there. It's really just metadata anyway, so you can adjust it in Lightroom later. In other venues, you might want to shoot with Tungsten or Florescent presets. But take a test shot or two and adjust accordingly.
That was my starting point. Quickie terminology: "Down one stop" means halving the amount of light. "Up one stop" means doubling the amount of light.
- Every factor of 2 in Exposure/shutter speed is one stop
- Every factor of 2 in ISO/ASA is one stop.
- Every factor of square-root-of-two (1.414) in F-stop is one stop (there's an area calculation involved). BTW, multiply sqrt(2) by itself a few times - you should see a familiar progression (1.4, 2, 2.8, 4, 5.6, 8, 11, 16, ...)
If you change one(and I encourage you to), you will need to compensate with one or both of the others to maintain the same amount of light. For instance, let's say my image is more or less okay, but I decide I want a really crisp shot and decrease my exposure from 1/125 sec to 1/250 sec (1 stop down). Then I will need to compensate by either dropping my f-stop from f/4 down to f/2.8 or increasing my ISO from 3200 to 6400, and I have to weigh the depth of field change against the added noise I would get from the ISO. Often though, the lower f-stop means a more expensive lens, so you may have to just live with the added noise.
But for more details about camera fundamentals, I suggest:
- The Negative (Ansel Adams Photography, Book 2), Ansel Adams, originally published sometime in the 50's, many many reprints. - Though it's about film, the concepts are still relevant if you're doing digital.
- Speedliter's Handbook: Learning to Craft Light with Canon Speedlites, Syl Arena, 2010 - I like what I've heard him discuss on podcasts. I'm actually only about a third of the way through this book, but what I've seen so far is very good. And the first chapter or two of the book is more about general camera stuff, and doesn't start into flash yet.