HVX Zebra Stripes/spot meter: Gray card at 50%?

M

mrbrycel

Well-known member
I was playing around with exposure today and set the brightest part of the gray card at about 50% using the spot meter. This made most of the whites at 70%, and some at 100%. Everything looked exposed well, but I was wondering if it was right. What percent should you set on the gray card?
 
BTW:

about how many % should human skin (e.g. for caucasian race) show outdoor on our HVX-screen, when we move the marker on it?

Is there any rule for skin?
 
They usually say that you should have 70% on the highlights of a Caucasian face. So I'm guessing you would want the medium tone of their face around 50%. When I shoot stills, I usually expose on the medium tone of a persons face which (correct me if I'm wrong) is telling the camera that it is medium gray?
 
I find 70% just kissing the nose or forehead to be about right (maybe slightly over exposed). 60-70% is a good starting place.

Jason
 
I'm not sure about IRE numbers overall since that depends on the ratio you want I guess, but I think that 18% gray was chosen at 18% because it is supposed to be in a general skin tone range so that you at least have a ballpark for exposures. The 18% (rather than 50%) is film related, but 50 IRE is about right...
 
Ok heres a test. I was shooting timelapses today, and I was trying to get a correct exposure. I didn't have a gray card, but I used the street, and set the spot meter at 50% on the gray street. It looks pretty good, maybe a tad bit over exposed, which might be a result of the gray street being a tad bit lighter than an 18% gray card. Tell me what you think:

(the 3rd timelapse)

http://vimeo.com/2154816
 
Whether middle gray should hit 50 IRE is entirely dependent on the gamma curve you select. For proper exposure on CINE-D or CINE-V, you'd probably want middle gray considerably darker than 50 IRE, whereas for HIGH gamma you might want it a little higher than 50 IRE. The gamma curve changes the distribution of brightness, and 50 IRE is in no way to be considered an absolute reference point for 18% gray because it's definitely tied to which gamma curve you use.
 
Awsome, this is just what I need.

Barry or anybody, is there a site that maps out the different gamma curves of the HVX200a for reference so we can match with the zoning system?
 
The HVX CD (or HVX+HPX CD) has a layered PhotoShop document with overlaid plots of all the gamma curves. Not in any sort of scientific fashion, but screen-shotted from a waveform monitor and then drawn in different colors and overlaid to show the relationship between them.
 
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