DOF in low light and flash question

[bphillips330]

ok, playing around last night. I have great understanding of f stops and depth of field. I just purchased the tamron f2.8 17-50. I was using the 430ex in my basement in a not so well lit area. I had the flash on auto (ttl i guess) and no matter what i put my iso (800-400-200) etc.. picture still looking a little underexposed. Put flash in M mode, BAMMM extremely overexposed at 1/1. So put flash back to ttl and pushed it to +1 and then to +2 and pictures looked much better.

Then i started thinking. If i used my 2.8 with no flash (or nifty fifty at 1.8) how much Depth Of Field, or how is it affected at f2.8 vs say f4-f8 to sharpen picture up some. Without flash that is. I know that in low light, crank iso to 800 or 1600 if needed, but then do you still have low depth of field since light is lower?

also, other questions This should probably be another post.

can somebody help me understand where depth of field is affected. by that i mean, if i am at 2.8 @ 3 feet i have so many inches to feet of focus. but if i am taking a picture of somebody at 30 feet from me at f2.8, then i have a much greater depth of field.

[In2Photos]

Here is a DOF calculator:

http://www.dofmaster.com/dofjs.html

For indoor flash try using M mode on the camera. Set it anywhere below the flash sync speed (either 1/200 or 1/250 depending on your camera). Set the aperture to f/8 and ISO to 100 or 200 (400 to recycle the flash faster). Now shoot. To get more ambient light in either lower your shutter speed (be careful not to go to low for camerashake/motion blur), open up yur aperture (be careful of DOF), or raise your ISO.