One of the most challenging things that beginning photographers must overcome is to understand the camera’s reaction to light...Too often they see something they want to photograph…point their camera at the scene and fire away letting the camera make all the decisions…as a result, the results don’t always match what they experienced emotionally. The impact of the moment just isn’t there in their images. It becomes one of those…’Well, you had to be there..’ moments.
There are a number of reasons this happens, the most important one being that most average photographers believe the camera simply captures what they see the way they see it. In reality, the camera doesn’t do that. What they don’t understand is that the exposure controls built into the camera can’t distinguish between a blank white sheet and a blazing sunset. It doesn’t’ know what it is looking at…it simply reads the intensity of the light that is filtering into its exposure sensors.
What the camera does is this: Based on the light values it reads, it wants to take an average of those values and set an exposure that falls in the middle between the upper and lower end of the exposure values that would work for a given lighting situation.
So how does knowing this help me as a photographer? This is where the visualization part comes into play. I want to avoid getting too technical here for fear of frustrating and confusing those who may not grasp all the photographic nomenclature…so, let me describe a circumstance to illustrate what I am talking about.
Take for instance a beautiful Kentucky morning with pastel colors arching across the horizon and layers of fog hovering down in the valley…something like this shot.
What you have here is a situation where the sky is very bright, yet the landscape and fog tends to remain somewhat dark. Understanding how the camera will react to this kind of lighting situation is important to understanding how to capture it. The idea here is not so much to capture what you see visually, but to capture what you are experiencing emotionally. Most DSLR digital cameras can utilize at least three types of exposure metering: Wide-Area Evaluative, Center Weighted, and Spot metering. Let me briefly explain each of these.
Wide-Area Evaluative is designed to evaluate the lighting situation across the whole spectrum of available light in the scene…in other words it looks at pretty much the entire scene to evaluate the light intensity. It is very effective in most situations.
Center Weighted does almost the same thing as WA Evaluative, except it places a higher value to the light it registers in the center area of the scene.
Spot Metering looks specifically at the light it registers in that center circle or square in the middle of your view finder…and ignores the rest of the scene.
Remembering that the camera wants to move the exposure value to the center of the scale…what happens when you use Spot Metering and meter off the lower part of the sky? Think about this for a moment. If what you are seeing visually is lighter than a middle tone value, then the cameras metering will cause the exposure to slightly darken the image…in essence bringing that portion of the scene it is metering toward the middle of the scale…something like this:…
Notice that the sky is a shade darker than the previous image because the previous image more closely resembles the actual visual brightness in the sky which was shifted toward the lighter end of the scale.
If the sky at that point is darker than a middle tone value…then the camera brings the exposure value toward the middle…lightening the sky. Something like this where the first image shows a dark sky and the second image shows the sky more toward the middle value.
If it was already near the middle value it would remain at the same value.
Put another way, if the sky is light…the camera wants to darken it…if the sky is dark…it will want to lighten it. Both visual values are pushed toward the middle. Same thing applies to Center Weighted…the only difference is that the camera is looking at a wider spectrum of the scene to gather its light values.
When using Wide-Area Evaluative…any large dark area or light area will often skew the exposure setting and you might end up with skewed results.
This example is a simplified illustration of how the camera sees light. So, how can you use this to your advantage? It requires the ability to visualize the scene from the camera’s perspective…not so much what you are seeing visually. Understanding how the camera will react to the light, you can then begin to think about how you want the image to look, and use the natural inclination of the camera to capture the light in a more moody and emotional way.
Let’s expand on this just a bit. All DSLR digital cameras will have a function called Exposure Compensation…usually designated with EV or AV initials next to a button with a +/- inscribed on it…like the one you see below on the upper right toward the middle.
If you look at the viewer on the back you will also see a scale on it with a 0 in the middle and expanding out with …+1…+2 to the right and -2…-1… on the left…like this;
-2…-1…0…+1…+2
When you press the +/- AV button, this scale is highlighted and using the finger wheel or control wheel on the back you move the cursor left or right to line up with the corresponding values on the scale.
This is one of the most useful and important functions on the camera. The only button I use more often than this one is the shutter release button. What it does is allows you to tell the camera to compensate up or down the exposure scale a certain amount above or below what it wants to automatically do.
Let’s take the same illustration we used previously. Pretend the sky was a rather dark and moody reddish orange color and really captured your imagination. Just looking at the sky, you realize that its color value on the scale falls below the neutral middle value. If you allow the camera to do what it wants to do…what will happen?
Remember…it wants to move the exposure toward the middle…so that dark and moody sky will more than likely become a lighter shade than what you want it to be…often effectively changing the dynamics of the visual impression. To get around that, you can tell the camera via the +/- compensation to keep the sky darker by dialing in a minus value…how much depends on just how far you want it to go…something between a -1/3 of a stop to a full -1 stop…by shooting a series of shots using different values you can bracket the images and then chose the best one later.
This is a very powerful function…and can be used to assign a color value to a particular portion of a scene by creatively using the various metering methods and experimenting. After a while, it will become second nature to you and you will find yourself compensating before you fire the first shot…because now, you are beginning to visualize how the camera sees light…and using its capabilities to capture the scene, the way you want it to appear…not what the camera gives you…nor necessarily how it appears visually.
Okay...the point is to get you to thinking in terms of visualizing your image before you take it by understanding how the camera is going to react to the light and using that reaction to your advantage.
Keith
