Long before cameras had built in meters, photographers got great exposures with a rule of thumb they could carry in their heads. It is called sunny 16, and it still works. If you shoot an old mechanical camera with a dead meter, a vintage rangefinder or a manual camera that never had one, learning the sunny 16 rule is the most useful thing you can do. It also makes you far more aware of light.
What is the sunny 16 rule
The rule says that on a bright, sunny day, with your subject in direct sunlight, you can get a good exposure by setting your aperture to f/16 and your shutter speed to the reciprocal of your film speed. Film speed is measured on a scale from the International Organization for Standardization (ISO). So with ISO 100 film, you shoot at f/16 and 1/100 of a second, or the nearest setting, which on most cameras is 1/125.
That is it. One aperture, one simple calculation. Everything else in the system is just adjusting from that starting point when the light changes.
Why it works
Sunlight on a clear day is remarkably consistent. The brightness of a sunlit scene varies far less than you might think from place to place, because the light source is the same. Film makers have long published simple daylight exposure guidance based on exactly that consistency, and film data sheets such as the one for Kodak Professional T-Max 400 still give exposure starting points for different conditions. Color negative and black and white films also have generous latitude, which means small errors in either direction still produce printable negatives.
Sunny 16 rule chart
Keep your shutter speed at one over the film speed and change the aperture as the light changes:
- Bright sun, hard shadows, or snow and sand: f/22 for snow or a bright beach, f/16 for normal sunny scenes.
- Slight overcast, soft shadows: f/11.
- Overcast, barely visible shadows: f/8.
- Heavy overcast: f/5.6.
- Open shade or sunset: f/4.
The shadows are your guide. Look at the ground near your subject. Crisp, dark edges mean full sun. Soft, fuzzy edges mean light cloud. No shadow at all means overcast.
Sunny 16 rule at ISO 400
ISO 400 is the most common speed for general shooting, with films such as Kodak Tri-X 400 and Kodak Portra 400. Under the rule, a sunny day calls for f/16 at 1/400. Most mechanical cameras do not have 1/400, so use 1/500, the nearest speed. That is a fraction less light, and the film will handle it easily.
If your camera only goes to 1/500 and you want a wider aperture for a blurred background, you will run out of shutter speed quickly with fast film in bright light. In that case, either use a slower film such as ISO 100 or add a neutral density filter.
Equivalent exposures
Once you have the base setting, you can trade aperture for shutter speed. Each stop wider on the aperture lets in twice the light, so you double the shutter speed to compensate. At ISO 100 in full sun, these are all equivalent:
- f/16 at 1/125
- f/11 at 1/250
- f/8 at 1/500
- f/5.6 at 1/1000
Choose a smaller aperture when you want more depth of field, such as for landscapes or street photography. Choose a faster shutter speed and wider aperture when you want to freeze movement or blur the background.
When to break the rule
- Backlit subjects. If the sun is behind your subject, open up one or two stops so faces are not too dark.
- Side light. Open up around one stop.
- Very light or dark subjects. A white wall in sun may need a little less exposure, a dark forest floor a little more.
- Indoors and at night. The rule does not apply. Use a meter app or a handheld meter instead.
When in doubt with negative film, give a little more exposure rather than less. Negative film handles overexposure far better than underexposure.
Cameras that already use it
Many simple film cameras are effectively built around sunny 16. Fixed exposure point and shoots such as the Kodak Ektar H35, sold through the official Kodak Ektar store, use a single aperture and shutter speed tuned for daylight, which is why they work best with ISO 200 or 400 film outdoors. Learning the rule helps you understand why those cameras struggle indoors and why film choice matters so much. If you shoot a manual rangefinder like the Leica M6 with a flat battery, sunny 16 keeps you shooting. Our comparison of rangefinder vs single lens reflex (SLR) cameras helps if you are choosing a manual body.
Related rules of thumb
Sunny 16 has a few cousins. Some photographers use sunny 11 for slightly hazy climates. For the moon, which is lit by the same sun, a looney 11 rule suggests f/11 at one over the film speed, a surprisingly accurate starting point. At night, city streets under bright signs often land around f/2 at 1/30 with ISO 400 film, though that varies far more than daylight does. Treat all of these as starting points, then adjust and learn from the results.
How to practice
Take a camera with a working meter or a phone meter app outside. Before you check the reading, guess the exposure using sunny 16. Then compare. After a week or two of doing this, you will be within a stop most of the time, and you can leave the meter at home.
Find more film cameras, film stocks and techniques in our Leica and film photography hub.
