Gray card, zebras and exposure

T

tomperson

Active member
Hi,
I've been reading about how useful are 18% gray cards for setting exposure in photography. I wonder, do I need those in video? Or can I just do with zebras (70IRE for skins, 100IRE for landscapes and such)?

Read this excerpt:

"Point your camera at a scene with a lot of snow, sand, water, or sky - the camera doesn't know what it's looking at. Take pictures without adjusting the exposure and you'll get badly underexposed photographs - snow will look dirty and gray, landscapes with big expanses of sky or water will be too dark."

http://www.apogeephoto.com/mag2-6/mag2-9st_1.shtml

If I was to film on a sunny beach with people, and I expose with zebras at 100IRE, what should I do regarding exposure? Should I see a lot of zebras on the sand, just a tad, what? Should I underexpose?
 
When it comes to shooting with zebras everyone has their own thoughts. Just remember that you want your people to be properly exposed. If that means that your sky or sand get over exposed that may need to be the case. Of course you want to minimize this by using bounce boards and lighting and being mindful of the sun position to help your shot - not fight against it. I personally always shoot with zebras at 100 and make sure that only a few highlights (zebras) are on the subject's face. But if your actor is underexposed by more than a stop or so on the dvx you wont be happy with the results. Its easier to forgive a "blown out" background than to try to explain why you can't see somebody's "muddy" face. Best of luck.
 
on Wider shots I tend to make proper scene exposure, often underexposing faces a bit, then in tighter shots I'll make proper exposure for the subject ei face. depends on what you are shooting and the look you want to create. A polarizer will often aid to a fair extent in a beach scene depending on sun position.
 
I get what you say "it depends on what you want to do". I have shot some beach scenes, and I have to say many of them looked quite dull, and the sand ended up looking "muddy", not white, and most of the image washed out. Zebras 100 IRE, sand showing a tiny bit of them. Maybe I should expose so that the sand gets more zebras?
 
I'm learning how really subjective it is. You will most likely always have zebras, its a question of where in the scene or subject.
I've been setting up on a street corner (no cup-- yet) to shoot people in a crosswalk under different weather conditions because ---its similar to the type of shooting I do. Sometimes 100 IRE, sometimes 80 IRE. I shoot as I think it should be adjusted, then shoot under auto iris to see what the camera wants. That way I can watch it at home and compare what I got. Make notes to yourself out loud as you do it. Sometimes I nail it and sometimes I dont. When I do, that cam is absolutely beautiful and when I dont, it really hurts.
Its giving me a whole lot of respect for the guys who can look at a scene and properly set exposure.
 
Hi Tom,

Seems like you're right on track with this zebra info. At some point, you may wish to consider using a light spot meter which allows you to analyze not only the light peaks but the ratio of peaks to valleys (i.e., f-stop contrast ratio).

After all, boys need their toys!

Good luck, Michael

PS - Incidentally, zebras can be very useful to ensure proper lighting balance when setting up a green screen.
 
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I would also check out posts on using a waveform monitor. This is the most accurate way of assuring proper exposure, because you will get a numerical value to your highs and lows. It will tell you what is blown out. Like Zebras set to 100 tell you what is at 100, but they don't tell you what is at 105 or 102. You have to adjust the iris to make them lower to see, but a waveform monitor will show it all. That is where the 18% gray card comes in. You fill the frame with the gray card and check your waveform monitor and set your exposure accordingly.
 
Thanks all for the kind replies!
I've been doing a lot of tests, but unfortunately I haven't had the chance of actually doing a lot of testing in the beach, just a couple of minutes and that's it.

I plan on shooting as much as I can with the camera connected to a laptop with DVRack (Adobe OnLocation), so I'll be able to use a Waveform monitor. I've read the product's manual, but I don't think it really addresses exactly what I should aim at when using it for setting exposure.

@sfoster, would you mind helping me a bit with how to use it?
 
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