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Understanding the Sunny
f16 Rule
By Brian Ratty © 1999
| Many photographers rely totally on their
camera’s built-in light meter. After shooting many rolls of film they can’t
understand why their pictures are not 100% exposed correctly! Your camera may say
automatic, but that does not mean automatically right! Any good photographer must learn to
"out think" the camera’s meter. To accomplish this an understanding of the
"Sunny f 16" rule is essential. So what is the rule? Well, simply put, the
rule tells us on a bright sunny day to set your aperture at f 16 and convert the ASA or
ISO film rating to the closest shutter speed.
I.e. Ektachrome 200, f 16 at 1/250...Fuji 50, f 16 at 1/60, etc. Now believe me, this
rule works! You can travel the world with or without a light meter and get 100% exposure
results but only if your subject is larger than a bread box, is front lit and has average tonal
brightness.
As with most photography, there are some variables to keep in mind. First, the sunlight
must be bright, with little or no haze. If you’re shooting on sand, snow or with a
bright building around, you will have to stop down. On the other hand, if you are shooting
on a cloudy or overcast day, you will have to compensate by opening up. If your subject is
not front lit, i.e. back lit, side lit, etc. you will also have to make exposure
compensation (see the variable chart). Keep in mind your subject’s tonal brightness.
A white or light colored subject requires less exposure than a dark subject. Remember that
your in-camera exposure meter is calibrated for average subject tonal contrast of
approximately 18% gray. When the meter reads a scene, it tells your camera to exposure the
subject as an average tonal scene. You as the photographer must learn to see your
subject’s brightness and expose correctly.
Once you know and understand the variables of the "sunny f 16 rule" you can
begin to "out think" your camera’s built-in exposure meter. In fact, the
rule comes in handy to check the accuracy of all your light meters.
I know a lot of professional photographers who don’t use light meters at all. They
have the ability, in the studio or on location, to see the subject’s tones, the
subject’s lighting, the subject’s size and then compute the correct exposure,
given any ISO rating, in their head. This takes years of experience and begins with a
thorough understanding of the "sunny f 16 rule".
One last point, the rule holds true for both negative and transparency films. But keep
in mind that negative films have a much wider exposure latitude than transparency films.
Therefore, mastering this rule with slide film is the best test.
VARIABLE
CHART
SUNNY f16 RULE
| Variables: |
Average Subject |
Light Subject |
Dark Subject |
| Front Lit (Full Sun) |
Use Rule |
Rule -1 Stop |
Rule +1 Stop |
| Side Lit |
Rule +1 Stop |
Use Rule |
Rule +2 Stops |
| Back Lit |
Rule +2 Stops |
Rule +1 Stop |
Rule +3 Stops |
Photo Tips:
a. The most reliable light meter in your camera bag is the film’s datasheet. Read
each datasheet and develop a total understanding of the characteristics of each type of
film you use.
b. Also, when working with new types of film or when just starting out, get in the
habit of recording exposure, lighting and processing information in a small notebook. Then
when you judge your results, you will have a foundation of facts to make correct
decisions.
c. By being organized and developing good habits you can be reassured as to the final
quality of any pictures you take. |
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