Hello jenmardi,
First, the fstop and shutter speed question ... For a lens of 70 mm I would use the manual with shutter speed at least 1/250 or 1/500, then the fstop I would set at 2.8 or just under this, no more than 4. You need as much light as possible, but not to drown it. The shutter speed needs to stay low (or other words, fast) to not get blur. For example, for a 70 mm focal length, you have to double it to > 1/140 (70*2) or if it's 100 mm then > 1/200 (100*2). This is if you just stand still or using a tripod. If you're hand holding, you have to go higher, like 70mm would be 1/200 or higher and 100 mm would be > 1/300.
This is 1/250, 1/500, 1/1000 etc or more than half (or double, however you want to look at it) of your lens focal length. The fstop can be pulled down 2.8, 3, 4, 5 etc the effect of lowering this is the depth of focus will change. But that's ok.
Next question, red or yellow in it. Make sure you have the disc in the direct view of the lights you're shooting under when you take the measurement. Make sure the custom WB is being used (of course) and that you are getting the Good reply from the camera once you click the shutter. For whatever is yellow or red you need to make sure you do not mix lighting. All lighting needs to be at the same Kelvin rating or the balance won't match between subjects/objects.
Read up on what the 500wt Kelvin conversion is and make sure you compensate the 250 wt Kelvin lights with the appropriate color filtration to make the 500wt and 250 wt Kelvin conversion come out to be the same. The sun is also a different kelvin than these, so you even have to compensate for it too, if it's part of the equation.
Happy snapping. You can visit my
site to see some of the results I get with high speed, low lite concerts.
