Rule of Sunny 16 | How to Set Exposure without a Ligthmeter

One of my favourite cameras of all time is the Olympus Pen F, a camera without a light-meter. It demands that I either use an external light-meter or that I practice the rule of sunny 16 to get a proper exposure.

One of the main reasons I bought the Pen F was that it doesn’t have a light-meter, because it’s entirely mechanical. Just cogs and springs, with a lovely viewfinder and next to nothing that can break. Having no fall-back for gauging exposure meant that I had to get good at sunny 16. Which forced me to get better at reading the environments I was photographing in, a great exercise for any photographer.

This is a great rule of thumb to know, since it lets you gauge exposure in situations where you find yourself without a light-meter, whether because your batteries have died, the in-camera meter broke, or your camera doesn’t have a light-meter at all.

What is the rule of sunny 16?

This simplest way to understand sunny 16 is simply to see it as a means of making an educated guess for how you should set your exposure based on what the weather is doing. Simply look at the sky and see what it’s doing. Is the sun out fully? Is there cloud cover? Is the sun setting or rising? And then use the answer to these questions to choose an exposure setting.

How do you use the rule of sunny 16?

Let’s break it down.

To use the rule of sunny 16, start by setting your shutter speed to match your film’s ISO value. For example, if the film that you currently have loaded into your camera is a 400 ISO film, like Ilford HP5+, you’ll want to set your shutter to 1/400 sec. For most cameras the closest you’ll be able to set it to is 1/500 sec., in which case that’s what you’ll want to choose. This applies to any film ISO speed, just choose the nearest matching shutter speed.

ISO 64 = 1/60 sec.
ISO 80 or 120 = 1/125 sec.
ISO 200 = 1/250 sec.
ISO 400 = 1/500 sec.
ISO 800 = 1/1000 sec.
etc.

With your shutter set you’re nearly done, since you won’t need to touch it again (in most cases) until your change the roll of film.

To set your exposure all you need to do now is look at the sky and set the appropriate aperture on your lens. For sunny days with no cloud cover, and the light from the sun is shining on your subject from the front (the sun is high & behind you) the ideal aperture to choose is f16, which is incidentally where the name “sunny 16” comes from.

To set exposure in other lighting environments you simply open the lens further to compensate for when the available light is less than it would be in the full sun.

For example, if there are a few clouds in the sky, or if the sun is high in the sky but behind your subject, open the aperture to f11. If there is moderate cloud cover, but it’s not overcast open to your lens aperture to f8. For overcast days open the aperture to f5.6. For shade set f4, and for areas in extreme shade choose f2.8.

If you’re indoors and there is lots of window light coming in (and I mean lots) f2.8 or f2 will work nicely. If you’re indoors and it’s dim, f1.8 or faster will be needed. It’s worth noting that sunny 16 doesn’t work too well for indoor pictures, because on one hand there often isn’t enough light and on the other our eyes tend to compensate for the dimness, tricking us into thinking it’s brighter in the room than it is, making it difficult to make a good judgement for exposure without a light-meter.

Sometimes you’ll need to compensate for very dim situations. In those cases, you can adjust you shutter speed a little to get a bit of extra light onto your film. Keeping in mind that when you lower the shutter speed by half the effect is the same as opening the aperture by one stop.

For example, if you feel that f2 (which, let’s say, is the max aperture of your lens) is just a little too dark, and you have a 400 ISO film loaded, changing the shutter speed from 1/500 sec. to 1/250 sec. would have the same effect on your exposure as opening the lens to f1.4.

Adjusting the shutter speed a little up and down can also be used for creative intent.

When I take portraits outdoors on a slight overcast day, where f8 is the ideal aperture according to the rule of sunny 16, I often choose a higher shutter speed then is needed for the film I have loaded so that I can open the lens to f4 or even f2.8 which lets me blur the background in my image a little. Doing this will depend of course on the ISO of the film loaded into the camera and the max shutter speed that the camera can achieve.

Just like with most photography related things, this technique needs to be practiced. The first time you use it you might struggle choosing the right aperture or you might not feel too confident with your guesses. However, after trying it a few times, studying the results you get, paying attention to the weather and practicing over and over again you’ll quickly get quite good at it.

As a quick note, the rule of sunny 16 works best with colour negative and black & white film stocks, I wouldn’t per se recommend using it for slide films since those require a much more precise exposure. Negative film with its wide exposure latitude is very forgiving. Should you ever feel in doubt, just exposure one stop higher then your first instinct. Negative film loves light and will handle overexposure with no problem while still yielding lovely images.

Easier alternatives to the rule of sunny 16.

Exposing without a light meter isn’t for everyone, and it doesn’t work in every situation. There are alternatives to the rule that you can use in cases where you don’t have a functional in-camera light-meter on hand for one reason or another.

The first, most accurate, and also most expensive alternative to guessing exposure is to get yourself an external light-meter. Incident hand-held light-meters can measure the amount of light in a specific scene, and spot-meters let you read the amount of light reflecting off of a specific subject that you’d like to photograph.

Both tools, which are often (but not always) built into one light-meter will let you measure the light in your scene and will help you choose the proper exposure very accurately. Of course, you’ll have to carry around an extra tool that also requires batteries.

Another very good alternative to both the hand-held light-meter and the rule of sunny 16 is to use an app. Most of us carry a cell phone with use wherever we go anyway. Using an app eliminates the need to carry around an extra tool while also giving you a tool that you can use to measure exposure very easily.

There are lots of free and paid apps available for both Android and iOS.

Conclusion & Recommendations.

The rule of sunny 16 is a great way to not only gauge exposure when you don’t have a light-meter to hand, but also a great way to improve your understanding of exposure in analogue photography in general. It forces you to pay very close attention to the environment you’re photographing.

With time you’ll get a feel for how much light or how little light there is in a scene and start to notice patterns when it comes to choosing settings in certain scenarios. Take your time, and soon you’ll have mastered sunny 16. I’ve found that it’s become an invaluable tool which means that dead batteries can no longer put an end to my photography (so long as I’m using a mechanical camera that is…).