This is probably the most important rule in film photography and in photography in general, the Sunny 16 rule helps you get the correct exposure in daylight even if your camera doesn’t have a light meter or if it is not reliable enough.
The idea behind this rule is very simple : when you’re outside, shooting during a beautiful day with a strong sunlight and no clouds, you will get a correct exposure if you shoot at f/16 and if you set your shutter speed at 1/“ASA value” (or ISO). For example, if you use a 200 ASA film, under these conditions, you would get a correct exposure if you set your aperture at f/16 and your shutter speed at 1/200s. If you use a 800 ASA film, set your shutter speed at 1/800s – or any speed that is close enough to this value such as 1/1000s. Pretty simple right?
However, these are not the only settings that are going to work in this situation. Let’s imagine your doing a portraiture shoot and you want to hide or mask the background a little, shooting at f/16 won’t give you the best results. But you can open your aperture while you compensate with your shutter speed. Let’s say you want to shoot this scene at f/4, using the same Sunny f/16 rule and adjusting your shutter speed, you know that your exposure will be correct if you set your shutter speed at 1/3200 if you use a 200 ASA film. Your film camera might not be quick enough to take this shot, but at least, you know that your exposure will be correct using these settings.
But just remember : this rule only works in plain sunlight! Fortunately, you can still use it in different weather conditions. You should use the f/16 aperture in the sun (with hard shadows), but you can open at f/11 if you’re in a less intense sun (look at the shadows, they should be softer), open at f/8 when it is cloudy (minimal shadows), f/5.6 when overcast (no shadows) and so on. We can sum up this technique using the chart below :
This technique is about the direct light of the scene. But you should also adapt your settings considering the reflections you might have in your shot. For example, if you shoot during a bright sunlight, you should set your aperture to f/16 and your shutter speed to a certain value depending on the film you shoot with. However, if the ground is covered in snow, you will get tons of sun reflections on your ground that will only make your scene brighter. Because of that, you should close your aperture even more – like setting it to f/22 for example – or compensate by doubling or tripling your shutter speed. This remains true if you have only dark colours or mainly shadows in your scene, you might have to slow your shutter speed or open your aperture a little.
I insist, the Sunny 16 rule is very important and is pretty to master. But you should think about the way you want to photograph : start by setting your camera by following the Sunny 16 rule, then look at the reflections you might have or the amount of shadows in your shot. Then, juste think about the look you want to get : you might want to open more your aperture – then you have to compensate with your shutter speed – or you might want a faster shutter speed, then you will have to open your aperture a little more.
In other words, the Sunny 16 rule will help you, but it won’t replace you as a photographer, still think about your shot and your framing. Photography is not only about following rules to get a good exposures, it’s about telling a story and capturing moments.