By now we know how to control exposure by changing f/stops and shutter speeds, and I believe you know about equivalent exposures! However, how do you find a correct exposure in the first place? This guide is intended for operation in the manual mode, so be wary.
First we have to determine the shutter speed, this depends on the action. If we want to freeze a fast moving object we will need to have a higher shutter speed, similarly we can have a blur/ghost effect of a fast moving object with a slower shutter speed. So it is up to you to decide the shutter speed and comes with a day or two’s little practice.
Now that we have covered shutter speed, we have to determine how bright the subject is. Look at the daylight table above. The object brightness is the vertical column at the left side of the table. Lets talk about various subjects. An average subject is one that reflects about 18% of light striking it and absorb the rest. This category includes people in medium-colored clothing, most buildings, landscapes with trees, and roads or street scenes. The majority of photographic subjects. While dark subjects reflects only about 9% of the light striking it and absorbs the rest. This makes them only half as bright as an average subjects thus requiring twice the exposure. These includes dark-colored vehicles, people in dark-toned clothing, dark colored animals and very dark or black stones. Now to the bright subjects, which reflects about twice as much light compared to average objects. As a bright subject absorbs much less light they require less exposure than average objects, generally one stop. This includes, fair-skinned, dyed and light haired persons, people in light clothing, light colored animals and light colored buildings. The last is brilliant subjects, which reflects about four times as much light as an average subjects and absorbs relatively little light. As you know by now such an subject will require less exposure compared to an average subject, generally two lens stop less. Examples includes people in white cloths on a white sandy beach, a white boat against a blue sky and white painted buildings.
After considering the shutter speed and subject brightness next would be the environment. Just look at the horizontal row at the top of the table. There are five classes of illumination, bright sun on light sand, bright sun, hazy sun, cloudy bright and open shade. Let us elaborate on this. Bright sun in a clear sky, and sun is far too bright to look directly. Shadows are sharply defined with a hard edge. This type I typically excellent for landscapes, architectural subjects, and anything else for which we want hard, clear definition. However, this is not good for portraits, unless a hard effect is what we want. Sometimes the contrast between the sunlight and shadows are so great, the shadows look black and featureless. Next is bright sun on light sand, as sand act as reflectors they increase the amount of light on the subject, about half stops. All conditions for bright sun applies to this except for contrast, which is usually fairly low as the reflections from the sand casts light into the shadow areas, filling them. The Hazy sun, when the sun is practically obscured by haze or thin high clouds, but the sun’s disc is still clearly visible and bright. Shadows are still easy to see but they are slightly diffused and not clearly defined. In a hazy day distant scenes may be obscured which can be used for good effects. This is good for rugged portraits of people. The shadows are mostly clear enough to bring out skin texture and facial lines, but are often soft enough so that the shaded areas show details. A cloudy but bright day where the sun’ disc is barely visible due to clouds. For us this might look bright enough but typically for a good exposure it requires about two stops more than a bright sunny day. It is possible to capture shadows but normally they are weak and have soft edges. This condition is excellent for general portraiture and scenes of short or middle distances. Distance scenes can be a problem, as they tend to be over exposed and comes featureless white. Next is open shade, a cloudy dull day where the sun can’t be located in the sky because it is entirely obscured by clouds. There are no shadows at all, may be very faint one under vehicles or furniture. The lighting is extremely soft and is good for portraits of children, women or any other subject you wish to show soft. Some times the lack of shadows make the subject flat with no feeling of depth. This is much like the cloudy dull day except that it can be found on a clear sunny day too. Open shades are shades which are open to a lot of sky but shades from the direct rays of the sun. Examples includes shady side of a building with overhead skylight. Shades under a low, densely leafed tree is not “open”. This condition typically needs three stops more light than bright sun does.
A final adjustment might be needed for bright or hazy sun. If the sun is to one side shining across the subject so that part of it is lit by the direct rays of the sun and the rest by the light of the sky, we should open our lens one stop from the table’s recommendation, so that the shadows still show some detail. On the other hand, if the sun is behind the subject and shining on your face, then you should give two stops more than the table.
This daylight exposure table will help in finding out which setting to use outdoors. It is as simple as finding out the needed shutter speed, subject brightness and what type of light is in the environment and adjust the aperture size. Some camera manuals comes with these tables which you can carry around or you can memorize it if you want to (it helps). Alternatively use your intuition to get used to the environment and the required setting (it takes time).
As the name suggest, this table only works outdoors daylight, that is two hours after and before sunrise and sunset. Beyond these times it is completely useless but I guess this table gives a picture of what, how and when we need to tweak the settings. That is it, now you will be wanting some examples and practical advices. Come back soon for more…