Re: tables of values? First off not all your numbers are totally related. Depth of field is
related to the focal length of the lens, distance to focus point, and
aperture selected. This is completely irrelevant to exposure however.
Aperture, exposure time (shutter speed), and film speed, are all linked
around giving the correct exposure. It all depends on what you are
shooting and the prevailing light, as to what combination of numbers you
will choose. In most cases, you will have a number of options available
to you.
For example, in bright sunlight, with ISO 100 film, an exposure setting
of 1/125th sec shutter, and F16 aperture will result in correct
exposure. You could also use 1/250th sec and F11, 1/500th and F8,
1/1000th and F5.6, etc, or 1/60th at F22, 1/30th at F32 etc.
The actual values you will use, will depend on what you are shooting,
and on the capabilities of your equipment. For example if you were
wanting to shoot a landscape, you probably wouldn't choose 1/32000th at
F1 for 2 reasons. firstly your camera probably won't do shutter speeds
of 1/32000th of a second (and you probably don't have an F1 lens), and
secondly such a combination would give a very shallow depth of field
which probably wouldn't look good for a landscape shot. Likewise if
shooting a portrait, you wouldn't choose 1/15th at F45, because at
1/15th you will be prone to camera/subject movement, and at F45 you will
have a very deep depth of field that would give distracting background
elements in a portrait. It's important to note that both settings would
yield the same exposure. In practice then, you are working a number of
compromises into the equation - the amount of available light, the
available shutter speeds and apertures on your equipment, the
requirement to "freeze" or "blur" motion, and the depth of field
required. If your camera has various "scene program" modes, and tells
you the shutter and aperture it is selecting, then I'd suggest trying a
variety of lighting situations, and turn it to each scene mode to get a
feel for how it determines what combination of aperture and shutter to
select.
Following is a bit of a table of EV values for various lighting
conditions. I call on this quite a bit to estimate exposure in very low
light situations. These EV values are based on ISO 100 film. EV0 is
defined as 1sec at F1, and each EV is 1 stop brighter, so EV15 gives
1/125 at F16 (or the sunny 16 rule). For each value, I have given a
sample shutter/aperture combination that will work for that lighting
situation (not necessarily the _best_ settings for any particular
circumstance though). Note also that when using film and long exposures,
reciprocity failure also needs to be factored in, but that's a tale for
another time. BTW, the following is not my work, I lifted it some time
back from either a website or a book (can't remember what or where) and
have carried it on my palm as a bit of a reference.
-6 Night away from city lights, subject under starlight only 30min F5.6
-5 Night, away from city lights, subject under crescent moon 15min F5.6
-4 Night, away from city lights, subject under half moon. Meteors. 15min F8
-3 Night, away from city lights, subject under full moon. 15min F11
-2 Night, away from city lights, snowscape under full moon. 8min F11
-1 Subjects lit by dim ambient artificial light. 30sec F4
0 Subjects lit by dim ambient artificial light. 30sec F5.6
1 Distant view of lighted skyline 30sec F8
2 Lightning (with time exposure). Total eclipse of moon. 30sec F11
3 Fireworks (with time exposure) 15sec F11
4 Candle lit closeups. Christmas lights, floodlit buildings and
monuments. 1/2 F2
5 Night home interiors, average light. School or church auditoriums.
Subjects lit by campfires or bonfires. 1/15 F1.4
6 Brightly lit home interior at night. Fairs, amusement parks. 1/30 F1.4
7 Bottom of rainforest canopy. Brightly lit nighttime streets. Indoor
sports. Stage shows, circuses. 1/30 F2
8 Store windows. Campfires, bonfires, burning buildings. Football etc at
night. Interiors with bright flourescent lights. 1/30 F2.8
9 Landscapes, city skylines 10 minutes after sunset. Neon lights,
spotlighted subjects. 1/30 F4
10 Landscapes and skylines immediately after sunset. Crescent moon with
long lens. 1/30 F5.6
11 Sunsets. Subjects in open shade. 1/60 F5.6
12 Half moon with long lens. Subject in heavy overcast. 1/125 F5.6
13 Gibbous moon with long lens. Subjects in cloudy-bright light (no
shadows)1/125 F8
14 Full moon with long lens. Subjects in weak, hazy sun 1/125 F11
15 Subjects in bright or hazy sun (sunny f16 rule). 1/125 F16
16 Subjects in bright daylight on sand or snow. 1/250 F16
17+ rarely encountered in nature. Very bright. Some manmade lighting.
1/500 F16 and faster.
Graham Fountain
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