Correct Exposures Without a Meter

For the first half of the 20^th century, photographers had to gauge exposures without a light meter. It was common at the time for film packets to have a set of exposure guidelines printed inside them to help photographers obtain correctly exposed pictures under a range of typical lighting conditions. Many photographers still use these guidelines, especially for tricky lighting conditions, when difficult-to-meter subjects like large areas of snow or wedding groups containing white dresses and black suits can produce incorrect exposure readings.

When two-thirds of the shot includes sunlit snow, exposure meters can produce more than two spots of under-exposure.

Unfortunately, when light meters were first added to cameras in the late 1950s, most photographers started to forget these basic rules-of-thumb that had been in common use for decades before. This is a pity, as they remain just as useful in the digital era as they were in the past.

They are based around the ‘Sunny 16’ rule. It stated: In bright sunlight, set the lens opening to f16 and the shutter speed to the reciprocal of the film speed (ISO value). In practical terms, this meant that if you are shooting on a sunny day with the camera’s sensitivity set at ISO 100, the basic exposure will be 1/100 second (or its nearest approximation, 1/125 sec.) at f16.

However, the rule doesn’t only apply to bright sunlight; it can be easily adapted to cover all types of lighting – as long as you know how to match the lighting to its brightness level and so determine the correct lens aperture. A quick guide to matching lens apertures with light levels – assuming the shutter speed remains constant – is laid out in the table below.

As you can see from this table, each step in the lens aperture column represents an adjustment of one f-stop. In effect, you are opening the lens aperture by one stop as the light levels become lower.

Using the Sunny 16 Settings
Applying the Sunny 16 settings requires you to shoot in full Manual mode (the M setting on the mode dial or in the camera’s menu). This allows you to adjust aperture and shutter speed settings independently. Set the camera’s sensitivity to a value that best matches the conditions in which you are shooting, selecting a low ISO setting for bright conditions and a higher one if light levels are low.

Note the ISO setting and set the camera’s shutter speed to the reciprocal value. For example, if you have chosen to shoot at ISO 100, the starting shutter speed will be 1/125 second. It’s not an exact match but the values are not required to correspond exactly. Near enough is usually good enough (especially when you shoot Raw files).

Now select the appropriate lens aperture for the lighting conditions, using the table above. Some situations will require minor adjustments to the Sunny 16 rule. For example, if the subject is backlit you will need to open the lens aperture by about a stop, regardless of the overall brightness levels. When using fill-in flash, allow for its effect, using the Guide Number provided by the flash manufacturer and the camera-to-subject distance. (If the flash has enough power to illuminate the subject you may be able to shoot according to the Sunny 16 rule.)

In overcast conditions, wide apertures are usually required. Note the shallow depth of field that results.
Program Shifting
The Sunny 16 settings can be a starting point for a huge range of additional options where all parameters – aperture, shutter speed and ISO – are variable. For example, you may wish to shoot with an ISO 50 setting when taking pictures in the snow. No problem! Simply open the lens aperture by one f-stop. The f16 setting becomes f11.

Suppose you wish to obtain a greater depth of field for a landscape shot in cloudy bright conditions? Either increase the ISO setting or select a slower shutter speed – or both. Remember that each ISO increment is equivalent to one f-stop – and the same applies to shutter speed settings.

Changing the shutter speed to 1/500 second when the ISO is set to 100 effectively reduces the amount of light entering the camera by two f-stops (from 1/125 second to 1/250 second and then to 1/500 second). Changing the ISO from 100 to 200 doubles the amount of light entering the camera, requiring you to change the shutter speed to 1/250 second OR close the aperture by one f-stop.

Difficult Lighting
The best way to deal with many difficult lighting conditions is to bracket exposures. However, sometimes it can be difficult to find the appropriate centre point to base the exposures on. The following tips can provide useful starting points:

1. Backlighting
Start at -0.7 EV and bracket in 1/3EV steps. There’s no need to bracket on the over-exposure side because you need to brighten up under-exposed areas without over-exposing the rest of the shot. Best results are obtained when the subject is in front of a dark background.

2. Sunrise and Sunset
When the sun is in the shot, shoot silhouettes. Begin with f4 and bracket in full stops out to four stops of over- and under-exposure.
3. Forests with lots of bright shadows
Shoot under open shade or overcast conditions and bracket in half-step increments to one stop over and one stop under.

4. Night shots
Use long exposures and low ISO settings to minimise noise. Put the camera on a tripod and use the self-timer to trigger the exposure. Apertures between f5.6 and f11 will usually deliver the best results.

High sensitivity settings at night can produce image noise with small sensor cameras but are less likely to cause noise with DSLR cameras, which let you use fast enough shutter speeds to capture moving subjects without blurring them. (Photograph taken with Sony DSLR-A100.)

Photographing the Moon
The moon can also play havoc with your camera’s exposure meter because its surface is so bright whereas the sky behind it is very dark. A similar rule of thumb can be applied when photographing the moon. Suggested aperture settings when shutter speeds are the reciprocal of the ISO setting are:

Full moon: f11

Half moon: f8

First or last quarter: f5.6

Crescent moon: f4.