Looking at Scene Contrast

The main issue in making good exposures in high contrast scenes is learning the difference between how your eye “sees” and handles contrast and how the sensor “sees” and records brightness values. Contrast is defined as the difference between the brightest and darkest areas in a scene. In photography the areas that define a usable contrast range are those in which you can see and record detail and tonal values; the compositional decisions often involve how you treat those brightness areas that fall outside this range.

For example, if you photograph a white car in bright light you would want texture and tonal value in the car body and details and perhaps even in the tire tread. But you might not care about the details in the asphalt that sits in the shadow of the car. Or, if you’re taking a portrait in bright light you’ll want good skin tones values in your subject but may not care about information (details) in the shadow he or she casts. When we talk about a usable contrast range we are talking about those areas that you want to record and not those that may also be in the scene but that can fall into tone without detail, like a deep shadow. We can call this usable range of values the "significant" tones, with the brightest in which you want texture the significant highlight and the darkest in which you want detail the significant shadow.

If you take an exposure reading of just the significant highlight you are placing that highlight on the middle of the recording scale—-in essence, you are telling the exposure system that you want the highlight to record darker than it appears in the scene.

And, if you take a reading of just the significant shadow area (like in the image shown here) you will be recording it as brighter than it appears in the scene. This throws off the balance of brightness values in recordings where there are both bright and dark values. If you make a reading of and record the darker areas alone it will cause the brighter areas to “burn up” and become overexposed, just like the side of the building here.

If you want to make a quick test of how making readings from the lighter or darker parts of the scene affects your results, set up a bracketing sequence at +/-2 EV and take three pictures of a brightly lit scene with shadows and highlights. One exposure may average the two values, one will expose for the highlights and one for the shadows. You’ll see how making exposures for just a certain part of the brightness scale affects the other areas.

Photo and text copyright George Schaub 2010. Exposure here was read from the shadow areas. The result in a high contrast scene such as this is fairly substantial overexposure of the highlights, never a good thing in digital (or film) photography.

Digital SLR Photography

Your decision to work with a digital SLR (DSLR) might just change the way you make, process, store and print your images. True, both film and digital photography capture light and require processing steps to see that recording as an image. But digital imaging differs in that it begins as an electronic signal generated by light and ends up as binary code that describes color, brightness and tonality. It is in how you deal with those codes to create an image that makes digital so different.

At first, DSLR cameras can seem familiar. Placed side by side, film and digital cameras often resemble one another; in fact, most DSLRs are built inside the frame of a 35mm SLR body. There are also similar buttons, dials and controls. Terms such as shutter speed, aperture, autofocusing and exposure are all quite familiar to the film photographer. But it is in the behavior of the digital sensor where the two mediums diverge. This is especially true in the image record--the digital image file. It is so unlike the film record that it’s easy to become confused by familiar terms that mask the need for very different operating procedures.


Digital images require considerably more “housekeeping” than film. Both types of image record must be stored properly, be kept safe from damaging influences and must be archived in a way that makes them readily accessible. But you can hold a piece of film up to the light to see the image. Not so with the digital image file. It is “virtual” (mathematical, really) and requires a good deal of computation to be read. It cannot be seen without the aid of a computing device. It requires the intercession of yet more machines and mediums to be maintained, and is always tied to the “grid”—sometimes called the “digital imaging infrastructure.”

This grid is dynamic and can change over time. It can render some cameras and devices obsolete in short order. It can drop image-recording mediums entirely. This pace of change means that there has to be a fairly strong awareness of changes in the computer and imaging industry at large and how some modes of recording and reading systems will change. As you get more involved you’ll see that copying, backup and why an awareness of how recording and playback systems and formats may change over time is important.

The housekeeping extends to archiving, storage and, ultimately, to you taking in hand the actual processing of the image itself. This does not mean you have to do the math or complex programming—the camera’s on-board image processor or your computer handles that. But to get that image onto a print, or corrected or refined to meet your standards, often means your intercession will be necessary. It is this hands-on demand that can make digital so different for many photographers. Granted, this is where your creative process as a photographer comes into play, and where the real potential of this medium resides. But digital is anything but a “you push the button and we do the rest” process.

This is not meant as a cautionary tale to scare you off the digital path. It is presented in the hope that this will become an eyes wide-open endeavor for you.