I thought this might interest some of you. I borrowed a light meter from a friend for an upcoming shoot. Of course, a light meter is useless you know the ASA of th camera you are working with. So I rated my HV20.
I used the technique I learned in cinematography class for assigning an ASA to a video camera. This is how you do it:
1. Take an 18% "middle gray" card and point the camera at it, filling the frame with the card. (light the card of course)
2. Let the cameras auto exposure expose for the card. Lock the exposure. The camera should have exposed the card to look middle gray (that is the way all auto exposures work)
3. Now read off the aperture and shutter speed from the camera.
4. Use a light meter to figure out how much light there is.
5. Calculate the ASA using the info from the meter along with the aperture and shutter speed you got from the camera. (the scales on the meter will help you with that.)
There are only three variables to exposure: Aperture, shutter speed, and ASA. All you need to know once you have the aperture and shutter speed is how much light you were actually working with and you can figure out the ASA. This is the part where a light meter comes in handy. (or at least a digital camera with manual controls over all three variables... it has a light meter internally after all) I used a proper light meter. It's easier because it's kind of like a calculator that figures out the the missing variable for you. And actually, in this case the more low tech manual/analog type meter is better because the spinning scales are easier to read and adjust. Once you have a meter in your hands the procedure for figuring out the ASA with the shutter speed and aperture should be pretty obvious to you (it's going to be a little different from light-meter to light-meter, so I can't give a step by step on that part. It will have to remain an exercise for the reader...)
Anyway, the results are: I rated my HV20 at about 80 ASA in "Cinemode". It is not a very fast camera by any any stretch of the imagination. To keep it at 1/48th and f2.8 with no gain (exposing for the gray card) you need around 160 foot candles. That is actually a lot of light. Forget about using house lights to get a good result. Unless your actors are a foot or two away from them it's not going to be enough. You'll need movie lights to really get the lighting up to where you have enough to be useful. I was testing with a 1k broad today, and it was just enough to get a good exposure with the light 7-8 feet away from the talent. (Wide open at 1/48th sec)
It could be worse. At least you can replicate that on the cheap with "shop lights" They are about 500w each and they sell those 2 headed ones that come up to about 1k total.
My FLO lights are just barely powerful enough to be useful. They need to be really close to the talent (4 feet or so) to be enough to provide a proper exposure. I need to build some bigger flo lights!
Has any one else rated their HV20? I'm interested to hear your results!