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Home >> Learning >> e-Book on Photography Table of Contents Photography e-Book Chapter 3 - Metering Sunny 16 Sunny 16 is a standard derived from the shade of gray that some exposure meters are referenced to (more at the bottom of this page). Sunny 16 is also known as daylight exposure and is quite simple to understand and remember. If ever your camera’s meter goes kaput either mechanically or for when the battery dies and if you are fortunate to have a manual camera that can go on without batteries, use Sunny 16 as your guide. Sunny 16 states that in bright sunny conditions, with a few clouds overhead but not blocking the sun, your front lit subject, meaning the sun is behind you the photographer, your exposure should be f/16 and the reciprocal of your film speed. If you are using ISO 100 film then your exposure is aperture at f/16 and shutter speed at 1/100 but since there are still many cameras out there that do not allow for 1/3 stop increments for shutter and aperture settings, you would use the closest equivalent, which would be 1/125. Using the set standard shutter speeds as available on a manual camera such as a Nikon FM2, if you were using ISO 200 film, your exposure value would be f16 and 1/250. ISO 400 would be f16 and 1/500 and so on up or down the film ISO scale. Sunny 16 provides a ready and known standard and there is an easy way to test the exposure of your meter. On a clear sunny day, mount a telephoto lens to your camera and set the lens to f16. If you have film in the camera you can use that ISO as your reference or set the film speed to a default ISO 100. Look north and point your camera, in either center-weighted or spot meter mode NOT Matrix or Evaluative Mode, mid way between directly overhead and the distant horizon. Your shutter speed should be the reciprocal of your film speed. You can also test your handheld spot meter this way too. I have done so with my Sekonic 508 and Nikon F100 camera and found them both spot on with the Sunny 16 rule. Why mid way between overhead and the horizon? Directly overhead and the exposure will be one-stop slower than Sunny 16 and over the horizon will be one-stop faster than Sunny 16. The sky is not a continuous tone, it is slightly darker directly above you and lighter as you look anywhere at the horizon, in any direction. Now that we understand what camera exposure meters can be referenced to, do we have to use f16 and the reciprocal of the film speed all the time? Of course not, if we used f16 all the time our shots would all look the same and if we did not break the rule of Sunny 16 for creative purposes we would not have all the dramatic images created to date. You can use the equivalent to Sunny 16 using other aperture or shutter speed combinations.
and conversely speaking,
The above examples are referenced to ISO 100 but you just merely have to replace the ISO for whatever film speed you wish to use and adjust the shutter speed accordingly. There are times when using Sunny 16 does not represent our creative intentions and we may wish to saturate the colors more so with some underexposure or wash out some colors with a bit of overexposure. This is when exposure compensation is useful for allowing easy manipulation of the exposure. If your camera does not have an exposure compensation feature then you can adjust the film speed dial and receive the same effect. Dial in a higher ISO speed for some negative (underexposure) compensation or a slower ISO speed for positive (overexposure) compensation. This feature works best with slide film and unless you contact sheet your negatives, there is little point to doing any sort of compensation with generous latitude negative films. Hopefully, you will have understood the basics of exposure by this point but what we have not discussed are the choices of aperture, shutter speed, and film speed. Understanding exposure is just the start but we need to interpret the scene and how to best communicate our intentions to people who will view our images. Aperture, Shutter, and Film Speed Aperture, shutter, and film speeds are set in increments called “stops”. A one-stop change represents either a doubling or halving of the settings. For example using a shutter speed of 1/125 as a reference, opening up the speed one stop would halve it to 1/60 whereas closing down one-stop would double the speed to 1/250. A two-stop change would mean opening up to 1/30 or closing down to 1/500. Film speeds work the same way and using ISO 100 as a reference, ISO 50 represents a one-stop change for slower shutter speeds and an ISO 200 film would mean a one-stop faster change. ISO 800 would represent a three-stop change from ISO 100 and would allow a three-stop increase in shutter speeds or wider apertures. The three variables of aperture, shutter, and film speed work symbiotically to provide an exposure value, change one variable and the others will change but we usually change only the aperture or shutter speed to work with the film we have in the camera. You would choose your film for the task to be undertaken and then adjust the aperture and shutter according to your creative requirements. Aperture The aperture is a diaphragm in the lens that opens and closes according to our desired effect for depth of field. This opening controls how much light comes through from the lens and onto the film. Use a wide-open aperture (opening up) and a lot of light will come through and hit the film but use a small opening (closing down) and the light will be reduced to a trickle. What is very important to understand is that as you adjust the aperture, an equivalent adjustment of the shutter speed is required to compensate. Aperture settings are not easily identifiable as being either double or half of a setting due to the use of fractional numbers. F-stops are actually fraction amounts with the f representing the focal length of the lens and the / meaning divided by the aperture setting. With f/16 and a 50mm lens, this means that
You can do this with any lens and obtain the actual physical opening for the focal length at an aperture setting. As you open up an aperture, the shutter speed must be set at a faster speed otherwise overexposure will result for a given film ISO speed. As you close down the aperture, the shutter speed must be set slower otherwise underexposure will result for a given ISO film speed. Aperture Priority mode is favored by many photographers due to the direct control of depth of field with the chosen lens. Depth of field is the perceived depth of sharpness in a scene. A wide-open aperture such as f2.8 has less depth of field than a stopped-down aperture of f16. There is only one true plane of focus in a scene, as chosen by you but the use of a small aperture will provide a large range of perceived sharpness to provide depth.
Notice the heptagon in the example shot of the lens at f8. In certain lighting conditions, those with pronounced broken highlights in the background (think a backlit scene with bushes or trees with the light coming through the leaves) will reveal the shape of the aperture if the lens has been set to any aperture other than wide open. Many people find such artifacts to be disconcerting and seek out lenses with more rounded aperture blades to provide more pleasing out of focus elements in the scene. Ever since the Photo Techniques Magazine on "bokeh", Japanese for and sometimes associated with bouquet, as in wine tasting to describe the characteristics of the wine. Bokeh can be an esoteric way to describe the charateristics of the lens. German lenses, especially those from Leica, are considered the standard for which all others are compared to. Nikon and Canon have jumped on the bokeh bandwagon and now design lenses to reflect the desire of the photographic world for more pleasing out of focus elements. This has largely been done by designing apertures with more blades for a rounder diaphragms. I am not sure if bokeh is merely a result of round diaphragms or is something that has to be purposely designed into a lens. Shutter speed
A fast shutter speed such as 1/500 is effective at freezing high-speed motion such as sports when the athletes are moving very quickly. A slow shutter speed such as 1/30 blurs the motion as the speed is too slow to freeze action and the athlete’s movement continues through the shutter cycle. The use of slow shutter speeds to create a blurring motion provides the eye with the illusion of movement and can be more effective than simply freezing the action outright. Shutter speed affects all movement and water flow is often shot at slow shutter speeds to provide a silky glow to the water. Use of the slow shutter speeds can affect other landscape elements such as swiftly moving clouds. Used creatively, shutter speed can open up a whole realm of possibilities. A slow shutter speed and some Photoshop enhancement provided the silky glow to this water fall scene
The choice of film to affect the exposure is sometimes forgotten but professionals have been using film to help with their assignments, especially sports photographers using high-speed films in low ambient light conditions. Your choice of film will directly affect the exposure whether you are shooting landscapes or shooting action. The grain and quality of the images provided by the film is also an important consideration. Landscape photographer want the most detail and the best enlargement capabilities possible, meaning using low speed films to minimize grain and recording as much as detail as possible. The overwhelming choice is for high quality chrome films such as Fuji Velvia, Provia F 100, and Kodak E100. Action photographers will sometimes use chrome films too but the nature of chrome films is not generally conducive to obtaining the desired results. The higher speeds favored by sports photographers are generally not of the best quality in chrome films and thus these photographers usually use color negative films for their tighter grain structure and better ISO speeds. Using ISO 800 and ISO 1600 speed films is a regular occurrence and many times the sports photographer is pushing the film even further to ISO 3200. Pushing film means to shoot the film at a higher ISO than rated and requesting the lab to compensate the development time to match the faster ISO. The danger is that not all films have been developed to be pushed (or pulled, the opposite of pushing) and the results can be less than stellar. Depending on the film you use you may also encounter reciprocity failure if your exposure times are very long or very short in duration. Slide films generally have their best results between 1/10 of a second and 1/10,000 of a second and going beyond these speeds in either direction requires compensation. Each film is different so you need to find out what the recommended reciprocity compensation is from the film company of your choice. More comments in the film chapter. Types of Meters
Center metering is the old standby that many older photographers know so well. Up until the acceptance of the Matrix type of meter, center weighted meters were the standard. This meter places the majority of importance to the center portion of the viewfinder with the remaining portions left to the rest of the viewfinder. This classic meter is also the one that photographers have to be aware of for weaknesses in metering complex or extreme scenes. Too much brightness without compensation would result in underexposure and too little brightness would result in overexposure as the meter reads everything as a middle tone. Snow or sand scenes are common ones for center meters to underexpose on while a black cat in a dark room is the cliché example of overexposure.
Most modern day autofocus SLRs come with a spot meter but some offer spot meters that are still too broad for a precise reading. In these situations, mounting a telephoto lens onto the body will narrow the angle of view and provide a more precise spot reading. After obtaining your exposure reading and having dialed it in, you can mount the lens you actually wish to use to take the exposure. Some SLRs offer multiple spot meters in the viewfinder as seen here and are small enough to be meaningful with most lenses. Canon's EOS 3 offers an averaging feature wherein multiple spot readings can be taken and then averaged, very handy.
Reflected light readings is self-explanatory, meaning the amount of light reflected off of the subject is the basis of the SLRs built-in meters. Incident metering measures the amount of light falling on the subject and it matters not what the brightness or darkness of the subject is. Bright subjects such as sand and snow reflect more light than dark subjects such as a stand of pine trees. Because built -in meters attempt to expose based upon a 13% gray reading, a light subject will end up as a gray tone on slide film as will a black subject. Center weighted meters are notrious for this but Matrix or Evaluative meters are also highly susceptible. Hold your incident meter in front of the subject at a 45 degree angle facing up with the half dome light collector up. Make sure the meter is in the same light as your subject otherwise your reading will be incorrect. In complex metering situations where no incident meter is available, you can use a spot meter to read off a subject with an average tone such as tree bark or green grass. Or take a reading off your palm and then open up the exposure as required. You will note that I suggest the palm of the hand and not the usual back of the hand. The back of your hand will become tanned when in sunny conditions and depending on how dark your skin becomes, the usual recommendation of opening up one-stop will no longer apply. Referencing the palm of your hand, which will not become tanned, will provide a more reliable source for metering. You are probably looking at a two-stop opening up with a palm reading. In the series of shots below, different metering options were used. The images are uncropped and the exposure meters were allowed to dictate the exposure. Mr. teddy's face was kept in the center to allow the spot meter to expose for it. Although the spot meter option exposed Mr. Teddy correctly, the burnt out highlights do not make for a good overall exposure. In this instance the use of flash to balance out the background with the subject provides the best overall exposure.
Gray Cards
It is now known that the real middle gray value is a reflectance of around 12% to 13% NOT 18% and this represents an off exposure of around 1/2 stop. What this means for those who like using gray cards is that you need to open up the aperture or shutter speed by 1/2 stop to compensate for the greater amount of reflectance of the 18% card. Such well known photography writers and commentators as Thom Hogan (Nikon Field Guide) and Bob Shell (of Shutterbug) are attempting to educate amateur photographers of this industry-propagated error. Second hand rumour suggest that Kodak had been badgered by Ansel Adams himself to use 18% as the middle gray value. Tough to say no to the pre-eminent landscape photographer of the 20th century. According those who think they know better, even Kodak has come to realize the error of their ways and instruct purchasers of their gray cards to compensate the camera's meter reading by 1/2 stop. This revisionism must have come about very recently because my own Kodak gray card, bought in 1997, has NO instructions advising of a 1/2 stop compensation required and yes I did read the instructions back then. So for those who wag their fingers at us ignorant consumers, keep the attitude in check because the 18% revising seems like a bandwagon movement but one that should be jumped on by all photographers. Regardless of what is the correct reflectance, 18% gray cards are still useful because they are still a known reference and really what is the big deal about opening up 1/2 stop of exposure? Nothing to be overly worked up about. There is confusion about just which standard camera companies use to calibrate their meters. Is it 18%, 13% or even something in-between? Camera companies are secretive about this information and it is left to the photographer to determine the accuracy of the camers's meter and how it will affect the picture taking process. Since I am confident my cameras and handheld meters can be checked against the Sunny 16 rule, I won't worry too much about it since this is another known reference that can be worked with. There are some photographers who like to debate all the technicalities about 18%, 13%, or 12% gray and just which one is truly middle gray. I suppose they like to know so as to ensure that they can achieve a technically accurate exposure all the time, however, just consider that technically accurate exposures do not always work to achieve what our creative intentions are. Often times too much is made of the technicalities of photography and not enough about the creativity of the medium. Update: Reader Bill Chiarchiaro sent some information to help shed some light about the Kodak gray card and its 18% reflectance:
Another reader offered this bit of information about the 18% grey card debate and whether or not 18% grey is the true middle grey reference, or whether it should be 12 or 13% grey:
A response to the above:
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Correspondence & About this website Copyright © 1998-2008 Edwin Leong |
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Shutter
speeds control the duration that the light coming through the lens will
hit the film for. Again, the aperture controls the amount of light hitting
the film but the shutter times the light hitting the film. As aperture
is predominantly about depth of field, shutter speed is predominantly
about motion and affecting how we perceive motion in the image.
Film
Matrix
or evaluative metering is probably what most amateur photographers
use in their modern-day high-tech SLRs. The multi-segment meter was
first implemented in the early 1980s and has evolved into a complex
and viable metering option for many people. In its very basic form,
the Matrix meter seems to be merely a beefed up center-weighted meter
but in its current mature stage of development, the Matrix meter can
ignore various segments and add weight to others to come up with a technically
correct exposure. Complex algorithms are utilized for the Matrix meter
to analyze a scene and provide an exposure value. The algorithms are
based on actual exposures taken from many thousands of shooting situations.
The Matrix is a number of segments in the viewfinder area that the camera’s
computer can use to come up with an exposure. Most Matrix meters are
in the 10 to 16 segments range but the Nikon F5 has 1005 RGB sensors
in its state of the art Matrix meter. Although quite complex and quite
capable, Matrix meters are not fool proof. When confronted with extreme
exposure situations, the Matrix meter is not able to cope and provide
a good exposure. Compensation from the photographer is required and
in the case with Nikon cameras, Nikon recommends using Center or Spot
metering for exposure compensation in order to obtain consistency. Compensation,
while in Matrix metering, can provide some undesired results.
Spot
metering is a very fine tuned exposure reading for a small portion
of the overall scene. In complex metering situations where even an incident
meter is not reliable or unavailable, spot metering is the best option.
The best spot meters are found in handheld units and offer very precise
1-degree readings. You can see yours truly using the Sekonic 508 in
spot meter mode in the image here.
Incident
metering is the favored method by many pros and serious amateurs
when using slide films. Color and B&W negative films have such
generous exposure latitude and thanks to the vagaries of the printing
process, the built in meters of SLRs can be used with not much regard
for exact readings. Slide films are not so generous and some careful
thought is required when in difficult metering situations. Because
Matrix, Center, and Spot metering is based upon reflected light, incident
metering can offer a better way of reading a scene.
A
note about gray cards. Photographers have been told and taught about
18% gray cards for decades, as a known reference to measure light with
reflected light meters, i.e., the meters built into most cameras. Using
a gray card held up at 45 degree angle in front of the subject allows
the camera to meter correctly and achieve a similar exposure value as
if you were using an incident light meter. However, there is growing
acknowledgement among the photographic community that gray cards at
18% reflectance is wrong.
