Understanding the Sunny 16 Rule


Once upon a time during the film era of photography…photographers had to keep a light meter handy at all times so they could take readings to get proper exposures. Experimenting on-scene was simply out of the question; it was expensive and time consuming. Being caught without a light meter — or several other pieces of gear that we take for granted in modern times — meant trouble; but just in case that ever happened, photographers devised various principles and guidelines designed to help them navigate their fully manual cameras. Among the most famous of those guidelines is the “sunny 16 rule.”

What is the Sunny 16 Rule?


Photo by Thomas Claveirole, on Flickr

It may come as a surprise to some that such an aged bit of photography advice is still around, but this rule has held on for so long because it just works. In short, the sunny 16 rule is a quick, easy, memorable method of achieving correct exposure when shooting outdoors. There’s a little math involved, but it is by no means mentally taxing. In manual mode, start by setting the aperture to f/16. Now set your ISO; exactly what you set it to will depend on how sunny it is, but let’s just set it to 100 in this hypothetical scenario. The final setting to deal with is shutter speed. According to the sunny 16 rule, shutter speed is to be set to the reciprocal (or inverse) of whatever ISO is in use. Thus, in this example, the shutter speed would be 1/100. If you decided to use ISO 400, then you would set your shutter speed to 1/400. ISO can be whatever you need it to be and shutter speed will also change accordingly; the constant in this equation is the aperture. It will always be f/16. Apply the rule correctly and proper exposure will be a constant feature of your outdoor photography.

Why Use the Rule?

So why, with all the amazing capabilities of our present-day digital camera technology, would anyone want or need to use such a seemingly archaic rule? There are a number of reasons, actually:

  • You can’t always rely on in-camera metering, particularly in tricky lighting conditions. There are times when your camera is going to get it wrong, especially when it comes to very sunny, high dynamic range scenes. Plus, your camera can’t know what effect you’re going for; you’re the creative one, not the camera. You need to tell the camera what to do.
  • You still shoot film. But if you have no intention of carrying around a light meter with you everywhere, then you will want to learn and use the sunny 16 rule.
  • You want to retain all the decision making responsibilities. As alluded to above, the sunny 16 rule takes the job of metering away from the camera and places it squarely with the photographer. Good or bad, you will take responsibility for the end result; it is akin to setting a custom white balance or using manual mode instead of automatic.
  • It’s a good backup plan. If you are a the type that always has a light meter with you, there’s always a chance it could malfunction or die on you. Knowing the sunny 16 rule will be the next best thing.
  • It makes you think. There’s nothing wrong with using in-camera metering, assuming it’s giving you accurate results but, again, your camera can’t read your creative mind. Learning to assess the quality and quantity of light for yourself will only make you a better photographer.

More Rules


Photo by r.nial.bradshaw, on Flickr

Not to be outdone by sunny days, there are other outdoor lighting scenarios that also have had rules assigned to them. There’s the sunset f/4 rule, the heavy overcast f/5.6 rule, the overcast f/8 rule, the slightly overcast f/11 rule, the snowy/sandy f/22 rule. Yeah, those are real. No, they’re nowhere near as catchy as “sunny 16,” but they do work and once you learn them you can customize them to suit your needs.

The sunny 16 rule isn’t the quintessential rule of all photography; you shouldn’t think of it that way. This isn’t an effort to get you to disregard the histogram if you’re using a digital camera. In fact, knowing how to read and interpret a histogram may be a greater asset to you than memorizing any given set of rules. And don’t obsess over the rather dry idea of “proper exposure.” Go with whatever exposure falls in line with your creative and aesthetic sensibilities. Light meters and histograms and rules are just tools to help you realize your goal. Use them to your advantage.

Other Exposure Resources

About Author

Jason Little is a photographer, author and stock shooter. You can see Jason’s photography on his Website or his Instagram feed.

The f/16 Rule (Sunny 16) is a God send. I’m a retired US Navy Photographer. I remember on my very first big assignment I had to shoot. An aircraft mishap on an aircraft carrier. I forgot to pack my Gossen Luna Pro, and the camera didn’t have a light meter. Standing on top of a jet, with tons of people watching me, I had to think fast. The f/16 rule popped into my head. I shot about 10 rolls of film without a light meter and had perfect exposures. It does work. Still use the f/16 rule to this day just as a check against the camera’s light meter. If I disagree with the camera, I’ll kick it into manual.

One thing that I did not see mentioned in the article. Once you figure out your base exposure using the f/16 Rule (Sunny 16), then you can dial in any shutter speed or f/stop you desire using the rule of equivalent exposure. Actually, with digital cameras today, you can also dial in a specific ISO using equivalent exposure as well.

Isn’t there a story about Ansel Adams happening on a scene with the sun setting and moon in the background? He had just enough time to get out his stuff, make an estimation using a “moony” rule and grab a shot. Then the sun had moved enough not to reflect off something that made the image. I think I read it in one of his books. I want to look for it now.

Although, I’m digital now, I’ve long used film and it’s related techniques, including the f16 rule, the f22 rule, the overcast rule, etc. After my meter stop functioning, once, I even employed the 18% reflective “grass” rule. After setting your camera, take a reading from “green” grass
(in sunlight, or, diffused outdoor light,) for a more accurate, 18%, exposure setting. Also, for more accurate skin value readings, it might help to read the “back’ of your hand for dark skin subjects, and, the “palm” of your hand for light complexed skin. This works particularly well if the photographer is dark skinned, because, the back of the hand is usually 1&1/2 to 2 stops less reflective than the palm.

having started with digital cameras and moving from auto to aperture mode these rules help me in the quest to go full manual mode all the time!

I have been shooting in manual mode for a long time now but have never before heard of the sunny 16 rule. I shall put it into practice and see if my images improve. I shall also use the other similar rules; sunshine in Skye at this time of the year can be temperamental.

I thought the constant would be film speed/asa? At least that is the way I’m doing. Since one cannot simply change the asa of a film, you change the aperture and shutter speed proportionally? Am I doing it wrong? I’m new to film photography BTW.

@gui I just got a chance to read this (I just came across a tricky scene and wanted a cruch) but you are kind of right and wrong. In the film days the constant would have been film, but now with digital understanding the exposure triangle means that you get a lot more flexibility. You can start with the rule and adjust your aperture to 5.6 on a kit lens but still need more light which means slower shutter but then you think I’ll get a blurred photo so you just adjust ISO instead. so rather than going to 1/25 from 100 you could go to ISO 400 from 100. Yeah you’ll get some grain but you’ll also get a proper shot.

Leave a Reply

Your email address will not be published. Required fields are marked *