Digital Exposure Techniques

Digital Exposure Techniques

by William Lulow

These days, so many image makers set their digital cameras to “Program” or “Auto” and just snap away. Often, this leads to bad exposures because even sophisticated cameras don’t “think.” A camera has no way of knowing what’s in your mind as the photographer. And, I doubt that many people who are just starting out in photography really know what a light meter is, how it works, or what it does.

I have to confess that even though I own several light meters, I rarely use them today. Instead, I have been resorting to using the camera’s built in meter settings as a way of determining exposure. I first look at the little graph that is shown in the camera’s viewfinder as well as on the display on top of the camera.  I then adjust the setting to make the exposure I want using the built in graph.

This is the graph on my Canon camera. You can see the numbers on the minus side and the plus side of the little indicator in the middle. These show the number of stops of underexposure or overexposure you can use to tweak your image’s exposure. You can make some changes in post-production software as well, but I like to get it right in the camera. Most of the time, I aim for just a bit of underexposure to saturate colors. I can always adjust it somewhat in Photoshop. But this is what I use as my “light meter.” You will also notice that the little dot on the upper right indicates that I have my metering set to “spot.” In addition, I have found that these “in-camera” meters of necessity, use the actual lenses you are using to come up with their readings. This is beneficial because using a hand-held meter, say, may yield more accurate readings, but those are only “ball-park” at best. Whereas, reading through the actual, digital lens probably serves the purpose better. Most hand-held meters are “incident” meters. They measure the light intensity falling on the subject from the subject’s position. Meters in most cameras are “reflective” meters. They measure the light intensity reflecting off the subject. Incident meters are usually more accurate. But we can’t always go stand at the subject’s position, take the reading and then go back a distance and recompose the shot. So learning how to use reflective meters is a necessity.

We must remember that the camera’s built-in exposure determining system, which can be changed from a “spot” metering to an “overall” one, will only do what we tell it to. If you want to put some creativity into your image making, you have to set your camera to “manual” more often. Having made images just about all my life, I can pretty much look at a scene and come very close to the correct aperture and shutter settings at any given ISO speed. But it takes quite a bit of practice to achieve this kind of knowledge. I usually have my camera’s meter set to “spot” meter and then I decide what part of the image I wish to have properly exposed. Since many exposures in any given scene are similar, you might just find that the shadow areas really don’t need that much detail anyway. But keep in mind that a well exposed image carries shadow detail as well as detail in the highlights.

So, I am constantly tweaking my exposures to get just the right balance of shadow and highlight detail.

This is an image where I decided that I was trying to achieve good saturation in the colors. I exposed for the highlights and let the shadow values fall where they may.

In this image, I was going for the basic buildings against the sky shot. I wanted the sky to be saturated so I added a gradient in Photoshop to darken the top part. I also made this image with a gradient filter over the lens to heighten the effect more. Again, the shadow detail was pretty much left out of the equation.

Here is a shot where I wanted to have plenty of detail in both the shadows and the highlights:

This image was obtained by carefully reading the light values in the shadow areas and the highlighted wall to the right and then exposing right in the middle of the two. (I was only using the meter graph in my viewfinder as a guide). There is detail in even the darkest areas.

These days, I have been using the camera’s meter and instead of centering the needle on the exact middle of the scale in my viewfinder, I try to underexpose the shot by about 1/3 of an f/stop. This helps saturate the image’s colors. If it is too dark, I can always lighten it up a bit in post-processing or conversely, darken it if it’s too light. Most good digital cameras these days have some sort of exposure scale visible in the viewfinder or near the shutter release button. The one in the viewfinder works best because you see it while you are aiming the camera at your subject.  If you have your camera set to spot meter readings, you can get a good reflective reading off your subject and then decide how to expose the image based on where you put the needle on the exposure graph and then viewing the image on the LCD. You can then adjust your exposure accordingly to achieve the results you want. Don’t forget that there is more you can do with the image in post-processing with Photoshop, if it is still not quite what you were anticipating when you download it.

So, with the addition of some of this careful tweaking of the file in Photoshop, I can usually get just the exposure I want.