The Power of Tonal Values

Ever heard of the Zone System? If not it is an exposure method championed by Ansel Adams where you can assign different tonal values to the scene you are photographing. Those values run from completely black to completely white with varying degrees of gray spaced between. In the middle is the neutral middle toned gray value.

In this post we're not going to become too deeply involved about how to use the Zone System, but we are going to look at how and why understanding the Power of Tonal Values is important.

First of all, this graduated scale applies to all colors and every color when applied through its full spectrum will have a middle tone value. To keep things simple we're going to look at only the gray scale, but keep in mind the principles apply to all colors.

What your camera's metering wants to do is give you an average of the light it detects. It doesn't matter if you use a full matrix metering or single spot metering. The results are going to be an average of all the tones and brightness values it see's. Matrix metering does a pretty good job of getting the overall exposure correct, but it is still just an average. So if you point your camera at a black wall the camera will want to make that black wall appear a middle toned gray. Point it toward a white wall, and again it will shift the exposure so it appears to become gray. That is why when we take pictures of snow, where the snow is dominant, it can appear to be gray.

I use matrix metering most of the time simply because it does a pretty good job of averaging out the exposure, however I will use spot metering under certain situations. Spot metering allows for metering a single small area and using that reading as the basis for setting your exposure. A good example of this is to meter a models face when there is a great deal of back light. (Peoples faces do have different tonal values of course depending on their complexion due to their race or lifestyle.) A bright back light can confuse matrix metering into thinking it needs to shift the exposure down to turn it into that middle toned gray. This will cause the models face to become much darker than it actually is. By metering on her face, locking the exposure in based on that middle tone, the camera will ignore the back light and expose for her complexion.

Neutral tones also contribute to landscapes. A good landscape image especially a black and white image, will possess a range of tonal values from almost pure white to almost full black. When the scene contains a variety of tonal values, matrix metering works pretty well to capture the full range of values. Sometimes in post processing you can enhance a certain value such as bright or dark areas to add a higher degree of  tonal complexity to your image. Doing so gives the image a great deal more depth.

Notice the image above. In this picture you will find tonal ranges that run the full spectrum from almost white to black with just about every tone of gray between. A slight tweak in Photoshop helped to enhance the bright areas, and bring life to the various middle values. When viewed as a larger image you can easily see how it has a great deal of depth to it. This is how you use the power of tonal values to its fullest. Knowing how your camera will react to the available light, will give you a greater ability to create images with depth.

When your subject has a dominant tonal value like a snow scene, you must always expose for the brightest area. If you simply allow you camera's metering to do what it wants, it will always give you a middle toned value, but you can compensate for that by using the Exposure Compensation button on your camera. That is the +/- button most often located on the top or on the back of your camera This allows you to tell your camera to add light or remove light from the exposure it wants to use. Take snow for instance. If your scene is dominated by the snow, your camera will want to make it look grayer than we want. To correct for this, simply move the +/- setting into the + side. The +/- settings are broken down usually into 1/3rd stop values like 0.3 stop, 0.7 stop, 1.0 full stop all the way to as much as 3.0 stops brighter or darker. How much to move it depends on the situation and requires a bit of experimentation. Sometimes + 0.3 is all you need, sometimes +1.3 is required. What you have to do is to avoid over exposing the snow...a little gray is okay because snow does have texture and we do not want to blow it out.

The photo above demonstrates this idea pretty well. There is a tinge of gray in the snowy areas because there is texture filled with shadows and exposed material across the snow, but the snow itself appears white. Again this image contains a full range of tonal values.

There are situations where an object or scene contains a splash of white while the rest is mostly middle toned values or darker. If  you simply expose for the darker areas, that white splash can often be blown out. In that case, you can use the exposure compensation in the opposite direction and drop it into the minus side, something like -0.3. This will slightly darken the middle values, but will keep the white splash from being blown out.

This color image of Sandhill Cranes is a good example of using the minus compensation value. Of course this was all preset before the birds took flight. The background was a bit darker than middle value, so I wanted it to look that way, but the birds were a middle toned gray, yet they have some white splash across their wings and under their chin. By presetting the exposure with a minus compensation, I was able to retain a full range of tonal values. Much of this comes with experience and experimentation...sometimes a good guess helps as well.

When there is a strong mix of light and dark values in a scene, there are times when employing a slight reduction in light will work to your advantage. The next image contains a wide mix of very bright and rather dark areas. If we are not careful, the darker areas will fool your metering into thinking it needs to brighten the exposure more than it should. This can often result in blown out light areas. So by employing a slight minus compensation value something like -0.3, you can still retain detail in the dark and light tones without blowing out the white areas. Also, remember shadows, either cast or deflected, are good on snow. They add detail and form to what can often look rather flat. A little gray is okay because it helps to define texture in snow. All you need is an illusion of white...almost white...with a tonal value slightly grayer than pure white to make snow look great.

There is no real cut and dried method to using tonal values in your photography, it is important however to understand the principle and then applying it to your photography. Sometimes we guess right and sometimes we don't, but to simply allow your camera to do what it wants to do all the time will result in average photographs. To capture the world in such a way as to bring depth and strength to the composition, employ the power of tonal values to what you are doing.

Another Wonderful Kentucky Sky

About a year ago I stumbled onto a location where a few isolated trees offered a nice opportunity for an interesting photo shoot. The trees were not unique and appeared much like any of the other ordinary trees you can find in Kentucky. The unique thing about these trees was they grew isolated in a small clump along a high spot that allowed them to be silhouetted against the sky. As luck would have it, they were also located at a bend and split in the road allowing for easy access. A small cemetery was also located inside the triangle space where the trees were growing adding to the country flavor of the location.

Even though sunset photos can more often than not, offer more of a cliche than a unique composition, I still enjoy photographing them. Usually broken clouds are required to produce that amazing glow in the sky we all enjoy. But, sometimes a cloudless sky can also create a tremendous amount of color and glow at sundown. The trick is to place something in front of the setting sun to break up the scene and allow the drama of color to unfold. It is also important to understand how your camera will react to this kind of light.

Let's take a look at a recent shoot and see how these images were created. The first thing to remember is what your camera's exposure meter wants to do. If everything is set to neutral settings and you simply allow your camera to set the exposure it wants using a priority or programmed mode, it will set an exposure that will bring the scene to a middle tone value. If what you are looking at is indeed a middle value then you can trust your cameras metering. If however it is very bright, the camera will darken it some to achieve that middle value exposure. If it is dark, then it will brighten it some to achieve the same results. Boosting or retarding the exposure by employing the +/- exposure compensation value button will tell your camera to add light or remove light from the exposure value it want's to set, or, you can set everything manually and compensate up or down either your aperture or shutter speed. We're going to assume you have at least a fundamental understanding of this principle.

The idea behind this particular shoot was to capture the glow in the sky behind the trees without blowing out the sky or making the sky appear too dark. Your camera has an uncanny ability to accumulate light and transform it into a range of colors you simply cannot see visually. In this case, I positioned myself where the sun would fall behind the clump of trees and I waited...taking a few shots here and there to test the results of the exposure. When the sun finally set below the horizon, all that was left in the sky was that glow. I wanted the shot to enhance this glow, to give the sky that radiant after sundown appearance. For the composition I placed the trees high in the sky and slightly offset with just enough of the ground along the bottom to comfortably anchor the scene.

Your camera will interpret this after sundown glow as a middle tone value and create a wonderfully graduated color effect that radiates away from the brightest center portion. What you must avoid is allowing the scene to become too dark or too bright where all the detail in the sky is lost in either blown out values or so dark they cannot be seen. A silhouette against this sky glow is what I was shooting for. A simple application of the +/- compensation to brighten or darken it will bring your exposure into a comfortable range. It takes a little experimentation to achieve the desired results. Using the tress to add interest and form enhances the compositions value by creating a simple yet pleasing layout. What might have been an ordinary, cloudless setting sun most people would simply ignore, became a wonderfully magical moment where the sky, the trees, and the light combined to generate a fun photograph.

I also managed to take some video footage for this years Adventure Photography Video series which was included in the previous post. All in all, it was a fun outing and I was able to once again take advantage of another wonderful Kentucky sky.

Beyond The Campfire Adventure Photography Series - Kentucky Sky

It took two tries, but I finally was able to capture the sky along with some video footage I wanted for another short Adventure Photography Series video. The first attempt resulted in an entire series of video footage that was out of focus...most definately user error. Anyway, I figured out what I did wrong and made some corrections and was able to return the next day to discover the exact same conditions as the day before.

This is a short video highlighting a shoot at dusk against another fantastic Kentucky sky. Just to keep things simple and to create a sense of continuity I used the same musical score which I will probably use for all of the adventure photography series videos.

Please enjoy...