using light meter with dvx100a

[Paul Rodgers]

I have a question about using my sekonic l-398 with the dvx100a. When I shoot photos I use my meter for everything. I would like to be as precise with video. Does anyone know a proper way of using a light meter for this camera? How do you get from 2000 lux (which i believe this camera produces) to an ASA/ISO.

http://www.newenglandfilm.com/news/a...h/lighting.htm
I found this article, but am still confused a bit.


Thanks in advance, Paul.

[Barry Green]

In 24P mode, the DVX is 640 ASA. However, be aware that you cannot use a light meter with precise results; there are variances in the reported speed rating depending on where you are in the exposure curve, and what gamma curve you're using. 640 will get you in the ballpark but you could be as much as 1/2 stop off.

Compounding the issue is that at the wide-open end, the speed rating is decidedly less. At 2.8, the speed rating acts as if it's 320, and that makes for trouble when trying to use a light meter. Whether this lesser performance at wider-open irises is due to a CCD characteristic, or just due to overly optimistic f-stop ratings (not representing the true light transmission or T-stop) is hard to verify.

So the general advice is: don't use a lightmeter for video, it's not really the right tool. Use a waveform monitor and a production monitor. That's what you use to judge video exposure. If you don't have one, consider DV Rack from Serious Magic, which gives you a realtime waveform (as well as vectorscope, production monitor, etc). You can use a lightmeter for general roughing-in your lighting, and for properly setting contrast ratios, but for absolute exposure it's not really the right tool.

[Winston Vargas]

The only reason to use a light meter with video is for lighting ratios. There is no way to accurately determine ISO for a particular camera. You want to be accurate in exposure you use a waveform monitor and for color a vectorscope.