Chapter 3
Exposure in Real World Situations
Understanding your camera's functionality is critical to obtaining a proper exposure. Exposure is not a static concept.
Your camera is capable of measuring light and making estimates of what it believes to be a proper exposure, however, it does this by using pre-programmed methods and can not possibly know what you are actually seeing and what result you are looking for. You can adjust the exposure modes of your camera to approximate the types of scenes you want your camera to meter but cameras are not that smart, therefore it is important you take the wheel when you see a photographic situation that is beyond the ability of the camera's limited ability to recognize.
In this section, I'm going to focus on landscape photography and methods of determining and controlling your exposure when outside during daylight hours, photographing in natural or urban/suburban settings.
I'm talking about scenes that may incorporate a combination the following visual elements. Sky, land, water, buildings, trees, flowers, architecture, man made objects.
The primary objective of course, is to learn how to analyze a scene and identify the obstacles presented by this scene and then make your camera expose that scene properly. Another visual & mental consideration when analyzing a particular scene is to be able to identify when a scene doe not present a good photographic opportunity and you must be able to say to yourself, “this won't work.”
Your primary mental objective when analyzing a scene for exposure is to identify the different sources of light. Natural light, man made light, reflected, specular highlights, shadow areas, mid-tone areas and highlight areas.
We'll begin with natural light. We are talking about sunlight here, and taking control of the sun is not an easy task. You do have options though.
Time of day is your first consideration. One common mistake I see with beginning photographers is planning their photography for the wrong time of day. They take their camera out on a bright sunny day with the mindset that it's a beautiful day thinking “I'll get some beautiful photographs.” Packing their gear in a bag they head outdoors in the late morning and take pictures until mid-afternoon, then head home for a little rest and dinner. Photography done in the middle of the day is the best way I know of to get terrible pictures.
You've probably heard of this already, but there are periods during the day known as “Golden Hours.”
Golden Hours occur early in the morning and late in the afternoon, when the sun is lower on the horizon. Prime natural light periods during the day will fluctuate with the season and geographical latitude. If you want better photographs, plan on doing your photography during these golden hours.
Early in the day, prime natural light occurs between pre-dawn and will last for maybe 3 hours after sunrise. Where I live in Colorado, I seldom do any serious outdoor photography after 9 AM on sunny days. When you are planning on morning photography, always keep in mind that the earlier you begin, the better off you'll be. With morning photography the light typically gets progressively worse as the minutes tick by. During late afternoon, the light begins improving late in the day and continues getting better until shortly after sunset. For morning photography, plan on being up before dawn. Plan on being on location before dawn. Plan on being ready to take photographs before dawn. Have patience and wait for the light to occur and be prepared when that light does occur. I frequently observe a period of about 30 minutes shortly before sunrise and shortly after sunrise where the sky will glow red and blue and purple. These momentary light shows are just that, momentary they only occur around dawn and in late afternoon around sunset. They peak quickly and dissipate quickly. If you miss them, you've wasted an entire day.
There is also no guarantee that the morning or afternoon light show will occur, but you can improve your likelihood of seeing good morning light by paying attention to weather forecasts and taking advantage of transitional weather periods.
When I speak of transitional weather periods, I'm talking about being aware of dramatic changes in the weather. Think periods before a storm, or immediately after a storm when dramatic cloud formations and light shows can occur. Think clearing conditions on mornings after a night of rain or snow where fog and mist or possibly bright, fresh, undisturbed snow and/or iridescent ice or frost may be present in your scene. These elements of weather can all make for great morning photography.
Photography at sunrise and at sunset presents a lighting issue though. Typically the sky will light up long before the surrounding landscape becomes lit. As the rising sun progresses on its daily journey, the shadows fade and the scene unfolds along a shadow line. As the day progresses, the drama of the sky degenerates and the drama of the landscape unfolds. The range of intensity between shadow and bright changes. You'll want to have a few simple tools in your kit to deal with the rapidly changing light and you'll want to understand how to use those tools effectively.
One of the most versatile tools you can have with you is a graduated neutral density filter. A graduated neutral density (ND) filter is simply a piece of glass with a varying degree of gradual shade from one side of the filter to the other. There are two main types of ND filters, hard edge and soft edge. Hard edge filters go quickly from dark to light and are useful when there is a very distinct light change in the horizontal plane of the scene. Soft edge filters have the attenuation spread out over a wider area and provide a smoother transition. The filter is placed at the front of the lens and adjusted in such a manner that it attenuates the brightest areas of the scene and gradually dissipates as the scene area becomes darker. ND Filters are an excellent technique for darkening the sky. There are many brands, some better than others and they come in a variety of attenuation characteristics. The most common are ND-.3 providing 1 stop of graduated change, ND-.6 providing 2 stops of graduated change, ND-.9 providing 3 stops of change and ND-1.2 providing 4 stops of change. My personal practice is to carry a 77mm 2 stop ND filter and a 77mm 4 stop ND filter in my kit at all times. I recommend you purchase a filter large enough to fit the front of your largest lens. You can always use step rings to adapt the filter mount to a smaller lens. This will save you a little money as you won't have to purchase different size filters for different size lenses.
Here's a common mistake scenario.
The sun is coming up. The overall scene is still dark but the sky is lighting up. Your camera is set to automatic exposure. That sky will be much brighter than the surrounding scenery. You see it all clearly, but the camera isn't going to see it the same way your eye will see it. Depending on the metering mode you have set, your camera is going to meter the scene and adjust the exposure to what it thinks is proper. If you allow your camera to do all of the exposure analysis, your camera is probably going to be wrong. This is a situation where you should take command of your exposure.
Your digital SLR can probably capture a 8-10 stop range of light, meaning the difference between the darkest black areas and brightest areas of the scene it can record are about 8-10 exposure stops in range. We refer to this as dynamic range. Anything too dark simply fills in with black and there is no detail in the shadow areas and anything too bright simply turns white and there is no detail in the brightest part of the scene. We refer to these zones as clipping. Your camera clips off the details after a certain level of light is recorded. A natural scene such as the one I've just described can actually contain a range of illumination which is much wider than your camera can accurately record. Perhaps in excess of 12-13 stops. Your camera may meter the scene so that the dark areas are bright enough to get shadow details but on the brighter side illumination scale, the highlight areas (brighter sky) is completely blown out and contains no detail.
The other extreme is that the camera can properly meter the brighter sky and thus maintain the details of the bright areas, but the darker areas of the scene are simply too dark and come out black. The ND filter allows you to reduce the dynamic range of the scene to a range that is more manageable by your camera. A carefully aligned ND filter will reduce the brightness of the brightest parts of the scene and maintain brightness in the darker parts of the scene. A 4 stop filter can take a scene with 13 stops of range and turn it into a scene with 9 stops of range, and allow your camera to better record everything within its exposure range. You can even stack filters on top of one another to further reduce the difference between light and dark. The drawback of course is that by placing multiple filters on top of one another, you also reduce the resolution of fine detail in your image. I've personally found that two ND filters can be used together with no significant loss of detail, assuming the filters are of good quality and clean. It's not that big a deal.
The method is to simply mount the filter to the front of your lens, or you can even hold it by hand against the front of the lens (what I normally do.) Adjust the filter so that the intensity of the bright sky is reduced and the intensity of the landscape gradually returns to normal. The darkest part of the filter is placed over the top of the scene. The graduated filter is tilted or rotated left to right to accommodate the horizontal aspect of the scene and moved from top to bottom to accommodate the gradual vertical transition from the lighter sky to the darker landscape.
A second approach to controlling the exposure in high dynamic range situations is to do what is called bracketing your shots. Bracketing is simply taking a series of identical photographs, each with a different exposure. Properly exposing the entire scene over a series of photographs will give you the ability to merge those multiple shots together in your computer and create what is called a HDR (high dynamic range) image. Using this method, you can take a scene that has very dark and very bright aspects and reduce the total dynamic range of the scene in your computer. I'll talk more about HDR technique in a later write-up, but if done properly HDR can generate a stunning image. Done improperly, it can make a horrible looking image. My first inclination is to get it under control at the camera and to use a graduated ND filter to start with.
I'm now going to touch a little bit on using your camera's built in metering system.
In the “old” days, photographers used hand-held light meters and being an old-timer myself, I still carry a hand held light meter with me in my kit. The truth is though, I seldom use it. I've learned to use my camera's built in light meter. All modern DSLR's have a built in electronic light meter and the different modes of the camera's metering system are adjustable and very functional. You simply need to understand what your camera is doing and how to use it.
Most cameras have three basic types of metering (read your manual.) Essentially, the three modes are Matrix or Evaluative (same basic thing), center weighted and spot metering. Your camera will probably allow you to quickly change these metering modes via a control adjustment button and/or dial on the body of your camera (read your manual.) Learn how to change your camera metering modes, learn how this effects your exposure and more importantly learn to adjust your camera for the correct mode for the scene you are photographing.
Matrix/Evaluative mode will divide the scene into different sections and calculate the illumination in each of those sections and make an exposure calculation based on a combination of the scene's overall brightness and darkness. This is okay for general photography, but in a more specifically challenging situation, it will most likely result in a incorrect exposure setting by the camera.
Center Weighted measures the entire scene but gives preference to the area in the center of the scene and adjusts exposure based on this preference. Very handy if what you want to be exposed properly is in the center of the frame, but not exactly what we're looking for with a bright sky at the top and a dark foreground. The camera will not get a good exposure setting in our situation.
Spot Metering allows you to select an area to measure by looking at a very small portion of the center of the framed scene and calculating an exposure based on that small area. By pointing your camera at the brightest portion of the scene, you can measure a correct exposure for that area. You can then point your camera at the darkest portion of the scene and measure the exposure for that area. You can then adjust your exposure to keep the brightest area from over exposing and then calculate the dynamic range in stops to the darkest areas. By using the graduated neutral density filter, you can reduce the brighter areas of sky and still keep the shadows within the range of exposure, and your spot meter is a good tool for making this happen.
Your camera will also allow you to make exposure compensations either up or down and this too is usually accessible from the camera body via a button or dial or both.
We've already touched in on the histogram, so by making use of your camera's metering modes and exposure compensations you can measure just about any scene and fine tune your exposure at will. There's really no excuse for getting your exposure wrong. You have all the tools at your fingertips to control and monitor the result.
The following dawn images were taken with the same setup, except the image on the left was shot without using a neutral density filter and the image on the right was taken using a 4 stop graduated ND filter.
Notice how the sky in the right photo is darker and how the overall exposure is better controlled.
A simple technique for golden hour photography that I commonly use is as follows. Hand holding my camera, I place my ND filter on my camera and make a rough adjustment to the alignment. I set my camera to spot metering mode. I set my camera to aperture priority mode and allow it to control the exposure by setting the shutter speed automatically, and adjust my aperture to obtain a maximum depth of field (depending on the scene), usually between f12 and f16. Once I set the aperture, I don't change it. I scan the sky using my spot meter measure on the brightest part of the scene (usually the sky where the clouds are brightest or the glow from sunlight is brightest.) This prevents me from over exposing my sky and clouds (remember the histogram, expose to the right.) I measure the darkest portions of the scene and quickly determine if I have a maximum of 8-9 stops of difference. If the difference is greater than 8-9 stops, I use a stronger filter or add a second filter to reduce the range. I then repeat the metering process until I know the scene will expose within the range of my camera. I then align my camera and filter(s) for proper composition and make a test exposure. I examine the histogram to insure that my brightest areas are not over exposed but just to the point of clipping. I then examine the darker areas of the exposure and insure that I don't have too much shadow and am not clipping the darker areas of the scene. I also examine the image to insure that the transition of the ND filter is properly aligned to give me a smooth and natural look between the sky and darker foreground. If I need to lower or raise my exposure a bit, I use the exposure compensation control in 1/3 stop increments to dial it in. If you're good at it, the whole process of adjusting your exposure for a scene can take only a few seconds.