Calculating Proper Exposure w/ Film

Note this is similar but different from Calculating Proper Exposure w/ Digital

Step 1. Take a light reading with your light meter in the highlight areas. Lets say it gives you an EV of 14 (thats typical direct sunlight on a sunny day).

Step 2. Take a light reading with your light meter in the shadow areas. Lets say it gives you an EV of 9 (thats typical shadows on a sunny day).

Step 3. Calculate your shadow bias. We expect film to be able to recover a range of 1 or 2 stops from shadow (under-exposed) areas. Our shadows measured EV 9 in Step 2. When calculating shadow range we add. So EV 9 + 1 or 2 = EV 10 or 11. 10 or 11 is the max EV we can shoot if we want to recover our shadows. The further from the measured EV 9 we get, the more detail we lose.

Step 4. Calculate your highlight bias. We expect film to be able to recover a range of 3, 4, or even 5 stops from highlights depending on film brand, film speed, color or B&W. Our highlight (over-exposed) areas measured EV 14 in Step 1. When calculating highlight range we subtract. So EV 14–3, 4, or 5 stops = EV 9, 10, 11. The further from the measured EV 14 we get, the more detail we lose, typically 3 stops is excellent with highlights, 5 is a bit risky.

Step 5. Sum it all up. After our calculations above, we see the film will give us a max range of about 7 stops, 2 in shadows and 5 in highlights. Since our measured EV9 to EV14 is only 5 stops (1EV = 1Stop), we can fit all our shadows and highlights into the latitude of the film and no sacrifice or trickery is necessary. Since highlights can go as low as EV9 and shadows can go as high as EV 11 and we know the further we get from the measured value the more detail we lose, we decide to shoot with EV 11 as typically 2 stops of range from shadows is safe enough and 3 stops of range from highlights should give us nice details.

Step 6. Apply the EV value to settings. This is much more complicated, typically calculators can do it for you but I’ll summarize to get you started. 1EV = 1Stop. A EV and Stop are measures of light. Increasing an EV or Stop by +1 doubles the amount of light (x2). So EV 3 is twice as much light as EV 4 and half as much light as EV 2. So EV 1 to EV 4 is 8x more light. 2x2x2. EV is typically used when measuring light or the amount of light. Stops is typically used to describe the difference in light or change in light with regard to exposure settings on your camera, though the two are interchangeable. So we would say, something like this: “Going from EV 1 to EV 4 gives us 3 Stops of additional light or 8x more light.” Now to give you a starting place to use this knowledge: F/1.0 at ISO 100 at 1s exposure = EV 0. When we change the aperture by 1 stop to F/1.4 at ISO 100 at 1s, EV = 1.

Here’s an example table all in ISO 100:

Horizontally we have the Aperture F-number (light and depth of field)

Vertically we have the EV number (amount of light, measured)

Diagonally we have the shutter speed (light and duration of exposure)