On a sunny day, from spring to autumn, from mid morning to mid afternoon, the correct exposure for any subject is f/16; the according shutter speed is the reciprocal to the ISO film speed number.
This is the basic rule that photographers have relied on since the dawn of photography. As a matter of fact, the f/16 rule was the must for taking pictures with old style cameras, since they were not equipped with built-in light-meters, unlike more recent cameras. All they had was an aperture control and a shutter, which the photographer had to know how to operate manually.
It was only in the past 1960s that light-meters became popular, so much so that, around the 1980s, the majority of photographers stopped relying on the sunny 16 rule and simply forgot about it. A very small number of old-school photographers, unaffected by the materialistic age, still used it. Satisfied by the high and unparalleled quality of their equipment (their old, meter-less cameras), they refused to ‘upgrade’ their gear.
I am thinking of Leica M rangefinders and Rolleiflex T, E or F TLRs. Leica was heavily criticised when it introduced the awful M5 as a substitute for the M4, drastically changing its trademark camera design. Back to its traditional look, Leica kept the same unaltered features from the M4 to the M7, the only relevant innovation being the built-in light-meter, a feature that many young photographers found extremely useful. What about the Rolleiflex E3 then? Can you think of improving such a perfect camera? That is why Francke und Heidecke never made any major changes to it, built-in light-meter aside, until the FX model, the last of the story.
Then it was the turn of the Japanese with their Nikon F Photomic cameras, which would change everything, by making buyers believe in the necessity of extra, automatic features in order to take good pictures. In a later article in this series I will specifically focus on how the rise of the Nikon F had a huge impact on the market and how the most important German camera manufactures lost to their Japanese competitors. However, here I would like to focus on how useful and fundamental the sunny 16 rule is in order to get the right exposure and determine not only the quantity but, most importantly, the quality of the light. This will make a huge difference between a beautiful picture or a rather bland image.
Please bear in mind that I will talk about film for the most part, but what will follow can be applied to digital cameras as well. The only difference with digital cameras is that you have to stop checking your monitor. Chimping is indeed not the proper way to judge the exposure; what you have to do is keep track of the histogram. in addition to this, you should enquire if your camera tends to underexpose your picture by default (variation of meter calibration constant), which is quite common with high end, pro Nikon cameras. Thus, it is not always the sunny 16 rule’s fault nor your fault if the photos taken with your digital cameras are underexposed when you shoot manually and set aperture and shutter speed according to the sunny 16 rule. There is a good reason for that, but it won’t be addressed in this article.
Rule Analysis and its Use
‘The correct exposure for any subject’
The rule is based on the light that falls on the subject, regardless of it being light or dark. The light reflected by the subject is not taken into account. This is called incident light exposure, which differs from reflected light exposure.
Incident light exposure renders an average reading of the scene, which is extremely useful when you want to capture a scene’s true tonalities. The film will receive a lot of light from a bright subject, thus rendering it black; conversely, a dark subject will get little exposure. The photograph captured with this type of metering will render the subject as it truly is. The Sunny 16 rule is a foolproof way to determine the correct exposure compared to built-in camera light-meters, which tend to underexpose white and overexpose black.
‘From spring to autumn, from mid morning to mid afternoon’
Focusing on the Sunny 16 rule, it is important to note that a few calibration changes should be made based on the seasons and the time of the day you are shooting. The quantity of the light that falls on the subject depends on the main light source, that is the sun, and the secondary source, the sky. The distance between the sun and the earth varies from summer to winter, that is why the default rule takes into account lighting situations from spring to autumn. In winter we would have to increase the exposure by one stop because of the greater distance between the sun and the earth. The same thing applies when shooting at sunrise or sunset; the rule takes into account these changes as well.
‘The correct exposure for any subject is f/16 with a shutter speed equal to the reciprocal number of the ISO film speed’
You have to set only two parameters on your camera; a third one should be kept in mind. Beginners will have to adjust only one parameter: the aperture.
Tips for beginners. The first steps to understand the Rule and master it
On your camera, set the shutter speed, reciprocal to the ISO speed number of the film (or sensor) you are using. In mathematics, reciprocal means the inverse number. Hence, if you are shooting with a 125 ISO film, the correct shutter speed is 1/125.
With a 400 ISO the closest shutter speed is 1/500; 1/125 at 100 ISO and 1/60 of a sec when using a 50 ISO film (although it would be better to overexpose slow film like the one mentioned, as if you were shooting with a 32 iso film)
It is best to use the shutter speed closest to the corresponding ISO speed number. There won’t be any significant difference, as long as you are shooting with colour negative film. Conversely, slide films are less unforgiving; in this case, you should increase the aperture by 1/3 of a stop.
The aperture should be changed depending on the lighting condition, which is indicated by the Rule.
It is important to note that the Rule starts from f/16, for it is rare to find lighting conditions where a smaller aperture is needed. Only white sand beaches or snowed fields reflects more light and thus require f/22 aperture setting.
However, under direct sunlight at midday, under a clear sky, any subject (a field, a street, a city or a landscape in general) reflects the same amount of light, regardless of its geographical location. F/22 is usually the smallest aperture, unless we are in a photographic situation where artificial lights are used (a studio flash placed at a close distance from the subject, for instance). In this case there are other exposure rules to follow, like, the Inverse Square Law, but i won’t go into such detail in this article.
If the sun is slightly overcast, less light falls on the subject; the amount of light is even smaller when the sky is either overcast or heavily overcast, and so on. Starting from f/16, it is possible to create a table with all the possible lighting conditions.
Sunny 16 Rule table: Lighting conditions and f/number setting
f/22 showy or sandy scenarios on a sunny day; blue, clear sky.
f/16 sunny day; bold shadows and blue sky. The subject projects strong shadows.
f/11 hazy day; the sky is hazy (light blue). The subject’s shadows are dark (not bold).
f/8 cloudy/bright day; the subject’s shadows are light gray;
f/5.6 overcast or open shade (if sky is light blue, shades are lighter); no visible shadows around the subject.
f/4 heavy overcast or dark shade (if sky is blue, shades are darker); no visible shadows around the subject; city streets, sunrise and sunset.
f/2.8 heavy overcast; narrow streets with high buildings. Woods and gardens with sparse vegetation. Landscapes and skylines right after sunset.
f/2 Woods and gardens. Landscapes and skylines ten minutes after sunset. Neon lights, spot-lit subjects (1000W at 2m distance).
f/1.4 Woods and gardens with dense vegetation. Las Vegas or Times Square at night. Shop windows. Fires, bonfires, burning buildings. Nighttime shows (ice skating, soccer, football, basketball, baseball, etc). Spot-lit subjects (500W at 2m distance).
f/1 Bright-lit indoor houses at night; bright-lit streets at nighttime. Indoor sports (amateur soccer, basketball, volleyball, swimming pools, etc). Stages and circuses. Beneath the rainforest canopy.
Please bear in mind that at f/1.4, the shop windows are the subject of our picture, the same can be said for fires, bonfires, and neon lights at f/2. They are the subjects, not the light sources. If you apply the rule correctly you won’t go wrong.
It may seem difficult, if you do not know yet. However, if you want to be in control of the quality of the light of the scene you are going to shoot, you have to learn the sunny 16 rule. You have to pay special attention to your surroundings, see if your subject is sunlit or is standing in the shadows. If this is the case, your light source is the sky. Compared to a hazy, light blue sky, a blue sky is less bright.
After assessing the quality of light, set the correct aperture on your lens. Your shutter speed is the ISO value, which was already set when you loaded the camera. Now frame, focus, press the shutter button. That’s it. It has never been so simple to take a picture.
Understanding your light source is the most important step.
To be sure, it is this knowledge, rather than a correct exposure, that is fundamental to making beautiful photographs. Look carefully at your subject’s shadows. This is a good method to assess your light source: black shadows at f/16, dark at f/11, gray at f/8, no discernible shadows at f/5.6 and f/4.
It’s obvious that a light meter would be able to determine a more or less correct exposure in the majority of the situations described above. However, a light meter cannot tell the difference between a hard light (clear, blue sky on a sunny day) or a dull light (overcast day). You can! By evaluating the quality of light – as the sunny 16 rule requires you to do – you can ask yourselves these questions: even though the exposure is correct, am I going to take a beautiful picture? Is the light in this situation pleasant? Will the shadows be visible? Will my picture be memorable and tri-dimensional or dull and flat because there are no shadows in it?
In my experience as a photography teacher, I have never met a student that has asked himself or herself these questions in an introductory level class. Because we rely so much on light-meters, we have forgotten about these aesthetic aspects of photography. A properly exposed picture is not necessarily beautiful. What you also need is a beautiful light, that gives a tri-dimensional look to the subject and that helps create an empathic bond with your audience. In this connection, the Sunny 16 rule is a must-know for those who want to be master of photography lighting.
The essay on the F16 Sunny Rule continues next week with the article ‘Reciprocity of the couple speed/aperture and practical use of the f/16 Sunny Rule‘.
Copyright photos and text © Michele Pero – all rights reserved