For example, if your sensor is set to ISO 100, the correct exposure would be 1/100 second (or rather the closest available shutter speed – 1/125 second) at f/16. The next three paragraphs address this example.

We know that a bright, sunny day equals EV 15. The “Sunny f/16” rule gives us an anchor point to use in mentally calculating the entire contents of Chart B, since it contains all four elements of exposure: Exposure Value (EV 15), sensor setting (ISO 100), aperture (f/16) and shutter speed (1/125).

From that anchor point, it is easy to calculate any other set of correct exposures. We know that each step up or down in one variable represents a doubling or halving of the amount of light required to make a correct exposure. For example, an overcast day would halve the light falling on the subject (EV 14). If the light reaching the sensor is cut in half, ONE other variable needs to be changed to increase (double) the amount of light. In this case the shutter speed could be reduced to 1/60 second OR the aperture could be increased to f/11 OR the sensor setting could be increased to ISO 200. Any ONE of these corrections would provide the correct amount of light. Make the correction that best suits your photographic purpose (decreased depth of field — the distance in front and behind of the subject that is acceptably in focus — or enhanced apparent subject motion).

In the same sense, a change in any of the variables can be offset by a reciprocal change in any other variable. For example, you may need a faster shutter speed to stop some action. If you choose 1/500 second, the light will have been reduced by two steps (cut in half from 1/125 to 1/250 and cut it in half again from 1/250 to 1/500). You could compensate for this by opening up the aperture two steps (from f/16 to f/11 will double the light and f/11 to f/8 will double it again). You could make the same correction by increasing the sensor setting by two steps (from ISO 100 to ISO 200 doubles the light and from ISO 200 to ISO 400 doubles it again). Or, you could increase the aperture to f/11 AND increase the sensor setting to ISO 200. Again, make the adjustment that best suits your purpose.

Now, let me say that the “sunny f/16” rule is one of the most misunderstood rules in photography. I have heard very competent professional photographers say that the rule is based on reflected light. Nonsense! The rule is based on the light falling on the subject (incident light) not the light reflected from the subject. The rule gives precisely the same measurement that you would get from an incident meter or a reflected meter using a perfect gray card. If your subject is very light or dark, you will need to adjust exposure to bring it within the five stop range of transparency sensor. But you would also have to make an adjustment from a reflected reading in the same circumstance. The difference is that an incident light measurement is a consistent anchor from which to adjust. A reflected measurement is much more subjective and prone to error. I have also heard that the “sunny f/16” rule doesn’t work for backlit or sidelit subjects. This is also false. Just open up a half stop, and make a series of exposures in half stop increments one and a half stop above and below the correct exposure. This is called “bracketing” and it is an important concept. You should always bracket in difficult situations. Anyone who says differently is misleading you. See the section on “Difficult Exposures” for guidelines.

The “sunny f/16” anchor point, combined with your knowledge that each change of one step in a factor doubles or halves the exposure, makes it easy to select a correct exposure for any photographic situation you may be confronted with.

Practice this technique with the Exposure Value Relationship Table in hand. Look at (or imagine) a photographic situation and try to mentally figure out the correct exposure using the “Sunny f/16” anchor point and any adjustments you feel are necessary. For the purpose of this exercise, it is best to concentrate on EV 11 through 16 (where most of your outdoor photography will occur). As you perfect your accuracy in this range, you can move on to more exotic lighting situations. Write down the factors (Exposure Value, sensor setting, aperture and shutter speed) that you believe will make the best exposure. Consult the Exposure Value Relationship Table to assess the accuracy of the calculations you made mentally.

With a little effort you will soon be achieving close to 100% accuracy, without the use of a light meter or any other exposure aid. The more you practice with the Exposure Value Relationship Table, the sooner you will be able to simply look at a lighting situation and immediately know the correct exposure for the job.

Once you have mastered this technique, you can use it to judge the accuracy of the light meter in your camera (or anyone else’s). You will be able to amuse and edify your photographic friends by accurately stating the correct exposure in any situation before your friends can take a reading with their meter!

Some Useful Photographic Guidelines

Sunny f/16 Anchor Point: On a bright day (EV 15) the correct exposure for any subject is f/16 at a shutter speed nearest to the reciprocal of the sensor setting (I.E. ISO 100 sensor = 1/125).

Doubling Rule: Within any exposure factor (Exposure Value, sensor setting, aperture, shutter speed) each step is double (or half of) the preceding step.

Tripod Rule: Use one for every photograph. If your shutter speed is slower than the reciprocal of the focal length of your lens (I.E.< 1/200 sec. with a 200 mm lens), use a tripod. If your subject is moving, double this shutter speed. If you are moving (such as in a boat or plane) triple the speed. If you are doing macro work (.25 magnification or greater), always use a tripod. If you’re using a format larger than 35mm, use a tripod. To be safe, weld your camera to the tripod.

Sensor settings: As you increase sensor setting, problems with grain and sharpness will increaseApparent Subject Motion: Increasing shutter speed will reduce apparent subject motion. Decreasing shutter speed will increase apparent subject motion.

Depth of Field (the distance in front and behind of the subject that is acceptably in focus): Increasing aperture (lower f/stop #) will decrease depth of field. Decreasing aperture (higher f/stop #) will increase depth of field.

WHAT TO DO IN TRICKY LIGHT SITUATIONS 

Front Lighting: Follow directions given in this document.

Side Lighting: Expose for front lighting, exactly as described herein. Bracket in half stop increments to one and a half stops over exposure. No need to bracket on the underexposure side. Alternatively, use a reflecting surface to bounce more light into the shadows. Make decisions based on the tonality of the subject. With a light subject your first exposure should be your best. With a darker subject your last exposure should be correct.

Back Lighting: Where possible, shoot subject in front of a dark background. Use EV 12 as your starting point (there are three stops difference between sun and shade) and bracket in half stop increments one and a half stops to the underexposure side (no need to bracket to the over exposure side — EV12 takes care of it for you). If you must shoot into a light background, your best bet is to shoot a silhouette. Examples are backlit fog on a lake with fishermen in boats in the shot. In this case, start with EV 15 and bracket in half stop increments to three stops on the under exposure side. Your backlit photography will be better if you use a long lens (with an appropriate lens shade!). Make sure your lens is scrupulously clean. If you are shooting people, use a warming filter (such as 81B), and adjust exposure by increasing exposure by 1/2 to one stop.

The Ultimate Backlight — Sunrises & Sunsets: When the sun is in your shot, go for silhouettes. Begin with EV 15 and bracket in full stops to four stops under.

Night Shots: Don’t shoot them at night, shoot at dusk. Look through your camera with the aperture fully stopped down. This has the effect of taking color out of the scene and allowing you to judge tonality more accurately. When your subject and the sky seem to be the same shade of gray, open up the lens and make your exposure. With a middle tone subject, this will usually take place 30-45 minutes after sundown. Use EV9 as a basis for exposure. Bracket in half stop increments to two stops over and two stops under. You will like at least half of the shots.

Shoot the Moon With a Long Lens: Use EV14. Bracket in half stop increments to one stop over and one stop under.

Shooting Scenics in Woods or Where There Are A Lot of Shadows: Shoot under overcast (EV12 or 13) situations.

Fast Moving Subjects — Sports, Etc.: Pick a vantage point that lets you shoot in front light, if possible. Utilize a dark background if available. Use a telephoto lens and a tripod, if possible. Use Chart B to select a sensor setting that will allow you to use a shutter speed TWICE the reciprocal of your focal length (i.e. a 300mm lens at 1/500 sec).

Shooting from an Airplane or Boat: Use table above to to choose a sensor number setting that will let you shoot at THREE times the reciprocal of the focal length (i.e. 1/1000 sec for a 300mm lens).

Macro or Micro Shots: Make adjustments for loss of light due to extension of the lens or bellows, as given in the instruction manual, or on the lens barrel. Better yet, use your in camera meter! It will need the exercise.