Zone system and EV readings

[Lucita Jones]

Hello,

 

I am familiar with EV readings and the Zone System, buy I just can´t understand what Harry C. Box means in his book "Set Lighting Technician´s Handbook", regarding the following situation:

 

 

"The skin tone reads EV 10, the highlight EV 15; the difference is five stops. You can even set the ASA on the spot meter so that EV 5 represents the f-stop on the lens. By so doing, you calibrate the meter to read out in zones; EV 0-10 equal zones 0-X."

 

Could some one further explain this to me? I would like to learn to do this and understand it because I am a firm believer in the zone metering system and this seems to simplify things at the moment of reading exposures.

 

Thanks,

LucitaJones

[David Mullen ASC]

I don't use the Zone System for cinematography myself. The original purpose in still photography was to control contrast through development changes and choice of paper & filters in printing, which you have limited control over in cinematography, especially with color stocks -- in other words, in flat overcast weather, I can't just place one area in Zone 1 and another in Zone 10 and then adjust the development until the first becomes black and the other white. The idea being that any photo should have a pure black and pure white reference somewhere in the frame.

 

But to answer your question, 18% gray, which is what you'd point a reflective meter at to get the "correct" exposure, is Zone 5. Typical caucasian skin tone would be a stop brighter, or Zone 6. Zone 10 would be 5 stops over 18% gray. I guess what he's saying is that you should set your meter so that an 18% gray card reads as EV5 so that every EV value equals a Zone. However, he seems to be suggesting that the skintone would be Zone 5 which may not be correct (since skintones come in so many values, it's not accurate to use them as a point to match EV's to Zones unless you want the skin to render as 18% in reflectance -- i.e. Zone 5 instead of Zone 6.)

 

You can work in Zones if you like, or you can simply learn how many stops over and under from 18% gray you can go before you get black or white. But this depends on the negative stock, the development, and the print stock.

[Wendell_Greene]

You can also do this if you use a Minolta Spotmeter F but in f-stops rather than EV. You simply meter an area that will correspond to what you want to be Zone V, like say f2.8, and then store that number in your meter. Then when you meter other areas of the scene the meter will tell you how many stops under and/or over they are from that setting.

[Marc Levy]

How about footcandles? Does anyone here meter using them? My professor's suggesting that using FC's instead of F/Stops is better, especially for figuring out ratios.

[Eric Steelberg ASC]

I don't know anyone who uses footcandles except for film teachers. And lighting ratios are only useful as a teaching tool. Again, no one really uses them. If you DID want to use ratios when doing a job, using Fstops is not hard so long as you know each full stop is twice as much light as the previous.

[Marc Levy]

I agree, f/stops are more convenient - but they are problematic when dealing with lower light levels. Especially when the meter can't give an fstop below a certain point. So, if key-side reads f/2, and the fill side is 4 stops under, the meter won't respond. This is where FC's are appealing.

[Marc Levy]

I agree, f/stops are more convenient - but they are problematic when dealing with lower light levels. Especially when the meter can't give an fstop below a certain point. So, if key-side reads f/2, and the fill side is 4 stops under, the meter won't respond. This is where FC's are appealing.

[Eric Steelberg ASC]

This is true, however if I ever find that I'm in that situation, all you have to do is re-rate the ASA on your meter higher to be able to get a reading your meter can display, then do simple math.

 

There are few lenses that give good performance that wide open though, except the S4s.

[J. Lamar King IMPOSTOR]

It's erroneous to say no one really uses lighting ratios or footcandles. Rather you should say, used less often.

 

Footcandles are a superb way to convey light levels independent of any exposure variables, i.e. t-stop, film or camera speed.

 

I keep track of lighting ratios often, especially if there is a chance that part of a scene will have be shot later or there will be lots of insert or cutaways shot at a later time.

[Guest oscar]

Footcandles is something everybody should know, though I dont use em, It's like the Mired Shift Value, been there done that, but in the real life, I dont use it, unless you have to really re create that stuff shoot outdoors and take it back inside studio and use a termo colorimeter.

[Tenolian Bell]

Actually I use foot candles all the time. I find it faster especially with a stock I've shot many times. I'll get a general exposure with T stops when I rough in the broad lights, then when I go in for more specific and intimate light I deal more in footcandles with a spot meter.

 

In general working with 500 speed film you know a T4 is 40 footcandles. Then its halves, doubles, or quadruples from there. I find that way I'm a great deal more accurate on exposure and contrast. It's easier to get within 80% of the look we wanted and less time dealing with contrast in telecine.

 

It's simple you know your key is at a T4 40 footcandles, your shadows are at 15 footcandels ( a stop and a half under), your rim light is at 120 footcandles ( a stop and a half over) and your back ground is at 60 footcandels ( a half a stop over). A quick check with the spot meter from the camera's perspective and you're done.

 

I have the second AC (if I have one) keep detailed notes on what I've done, so if needed with a high degree of accuracy I can recreate the scene.

 

In telecine if the colorist did something I didn't like I can reference my notes and know exactly how everything was exposed. Which has happened several times.

[Tenolian Bell]

Another bonus of footcandles in preproduction. Using photometrics and the specs of the set you will be working on you can predict practically everything about the lighting.

 

Know how large the space will be and everything is arraigned in the space you can decide what lights to use how far they will have to throw the beam, and the quality of light on the subject. That is all determined in footcandels.