Exposure Values?

[Chris Keth]

How do you apply exposure values to metering and shooting on set? I've only heard people brush over the subject, is it defunct now or something?

[neal]

How do you apply exposure values to metering and shooting on set? I've only heard people brush over the subject, is it defunct now or something?

<{POST_SNAPBACK}>

 

Exposure values (eVs) translate f-stop numbers into a linear scale, which makes it much easier to compare them. It's very helpful when using a spot meter to do a scene brightness evalutation. Say, for example, that you take a reading of the grass in a scene, and it reads eV 2 .... and then you take a reading of the sky and it says ev 9, then you know that the sky is 7 stops brighter. It just makes the mental calculations alot easier.

[Dominic Case]

0 EV is 1 lux (about 0.1 fc)

In still photography this requires an exposure of 1 second at f/1 on 100 EI film.

That's the nominal starting point for this scale but not very useful.

 

It's simply a scale of stops you can read off your exposure meter. If the light halves or doubles (one stop) then the EV changes by 1. With aperture, it's a factor of x sqrt-2, with speed it's a factor of x2.

 

Moving up the scale, that means that 10 EV is ten stops brighter, which is 1000 lux (about 100 fc)

 

so it requires 1/30th sec at f/5.6 on 100 EI film. (i.e. 5 stops of speed and 5 stops of aperture)

or 1/50th sec at between f/4-5.6 (for motion picture cameras)

etc

[Greg Gross]

Hello Mr. Bunnies,

Zone system consists as follows: 0(0.1 density) this is Dmax and sometimes

called maximum black. I have my camera calibrated for maximum black,my

lens, my darkroom enlarger and lens. My film at a certain development time

will give me maximum black on the negative. This will print on to paper as max-

imum black. I, on the Zone scale is nearly black(0.11 density). II on the Zone

is very dark gray(0.21 density). III on the Zone scale is textured dark gray(0.34

density). IV on the Zone scale is dark middle gray(0.48 density). "V" on the Zone

scale is middle gray(0.62 density). VI on the Zone scale is light middle gray(0.76

density). VII on the Zone scale is textured light gray(0.97). VIII on the Zone scale

is very light gray(1.18 density). IX on the Zone scale is pure white(1.33 density).

If you had 9 4X5 negatives(sheet film) and each one was exposed for a zone and

you printed each one on to paper you would see 9 distinct zones in the prints.

Now lets say we're shooting with a 4X5 camera and T Max 4X5 sheet film. We're

at the seashore and we have 10 sheet film holders loaded(they slide in and out

of the back of the camera) on the first holder I shoot with(sheet #1) I mark on

a piece of masking tape on the holder, my exposure and zones emphasized. Lets

say first shot is placed on zone IX (pure white) for surf rolling in. I will set my

spotmeter to zone IX and opposite this value I will read fstop and shutter speed.

If I want to change DOF a new fstop can be set and still maintain zone. Greg

[Greg Gross]

Mr. Bunnies,

If you work with b&w film long enough using the Zone system you will

start to see the zones in your subjects. You can use it also for color but

then the color temperature factor enters in. I believe if you understand

the films you use, emulsion,sensitivity,lattitude and how they are processed

and printed,understand the darkroom side of it,you can become a damn good

creative cinematographer. In actual photographic practice slightly overexposed

color negatives often print better than negatives exposed normally or under-

exposed. Overexposure will not effect the image color(done properly)it will

probably improve the shadow detail and reduce graininess. Overexposure of

b&w film often causes graininess. Overexposure of color negative film creates

larger dye clouds in each emulsion layer. As the dye clouds get larger,they

overlap and fill in from layer to layer,giving the appearence of less graininess.

You can make adequate prints from slightly underexposed negatives but you

can rarely make great prints from a thin negative. They make look muddled,

cloudy,flat and lacking contrast. Shadow areas are a problem. Prints from un-

derexposed negatives may lack shadow detail and show shadow areas as a

flat color cast. Modern movie printing processors use the point system and can

print various densities over a certain point range. I'm just learning about this

process and I'll be visiting a lab. Greg

[Chris Keth]

Wow, useful stuff. Thanks. I'm surprised I've never heard anyone work in EVs.