Old post I know, but incase it helps anyone a good rule of thumb when shooting without a light meter (although not advised) is the "sunny 16 rule". This says that at f16 on your lens, you can shoot at a shutter speed that is the same number as your film ASA. So for example, 100ASA film at 1/100th shutter speed at f16 on your lens should produce proper exposure.

Each time you double or half your shutter speed, it is equal to one stop in light change. Also by doubling or halfing your film speed it is also equal to one stop in light change.

Knowing that and using the "sunny 16" rule, if you half your shutter speed to 1/48th it means you can either half your film speed from 100ASA to 50ASA, or, you can close your aperature from f16 to f22. (remember that decreasing your shutter speed makes it slower letting more light in therefore you need to compensate equally).

If you want to shoot with an aperature that is much more open than f16 to maintain achieve a shallow depth of field than you would need to use Neutral Density filters to reduce the light. For example, at 1/48th on a sunny day using 50ASA we can shoot at f5.6 by using a ND8 filter since it blocks 3 stops of light.

I believe you got it wrong. If you slow your shutter (i.e. extend the exposure), you need to close your aperture further to maintain proper exposure. So, if f16 was needed for proper aperture at 1/100, you'd need f22 at 1/48.

I updated my post.

I know this is an old-ish topic, but I just thought I'd chime in and mention that it also depends a lot on your emulsion. Shooting Tri-X or any other reversal, you take your life in your hands by not metering because if you over- or under-expose reversal, there's no rescuing any detail.

If you're shooting color negative (or to a lesser extent, B&W negative) for telecine rather than printing, just make sure never to underexpose?always overexpose by about a stop, and you'll be fine. This is a common practice, because it gives you room to work with changing lighting conditions on location. I've seen good colorists bring back detail in color negative that's been overexposed by as much as 5 stops without any detriment to image quality.

Oh, and if you're shooting with a reflex Bolex, be sure to add an additional 1/2 stop to whatever you think you should be shooting at, because the shutter is 135 degrees, not 180, and the viewfinder prism cuts an additional 1/3 stop.

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Andrew Gingerich
Exploding Goldfish Films
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