Light meters and 35mm adapters.

[Finnegan]

So, I just finished shooting a project where the whole time I was second guessing my light levels. I'd light a scene, and take a look at it through the viewfinder and it'd look a little under exposed to my eye, but on the monitor and the slide out monitor it looked properly exposed. Normally I trust my eyes through the viewfinder, but consistent second guessing eventually took its toll.

I want to start using a light meter regularly but with a 35mm adapter I don't know if it can even be done properly. If I light a scene and my subject reads a F2.8 how can I make sure that its a true F2.8 that I'm shooting at through the 35mm lens when the camera lens (Canon XH-A1 / SGblade 35mm adapter) itself is around a F2.6 when I'm zoomed in for the 35mm adapter? Do I simply just have to do a bunch of light meter tests to find out exactly how much light I'm losing through the adapter and then compensate for it?

On a side note: does anyone know the ISO rating of the Canon XH-A1?

 

[Huy Vu]

A light meter is useless for 35mm adapter use since the gamma response isn't linear. You can calculate the ISO of the camera + adapter, but you don't really know what's going on once you start stopping down the lense. One stop on the lense does not necessarily equal 1 stop of light loss on the system since the diffusion of the GG is different. So a waveform monitor is really the only good tool to judge exposure.

 

[Lenilenapi]

Huy Vu is right. For video in general a lightmeter is a tool but unlike film cannot be the last word on exposure. A reliable monitor and a waveform monitor if possible are you final tools for exposure.

Lenny Levy