Matrix and evaluative metering systems are very user friendly and do a great job. But camera manufacturers have built in proof they’re not infallible. The proof lies in the exposure compensation button. If the overall exposure is too dark, add PLUS compensation and conversely, if it’s too light, dial in MINUS compensation. But here’s where many digital photographers run into a big problem. They base the too dark or too light interpretation on what the image looks like on the LCD rather than checking their histogram. I can’t stress enough that doing this is not the way to get the best possible exposure. The histogram reveals the actual capture data. Using the LCD introduces too many variables - the setting of the screen’s brightness, the camera manufacturer’s default settings, the ambient light at which it’s viewed, the quality of the LCD. I’ve seen too many photographers shoot every picture at minus one half to minus one full stop reasoning it “looks” better on the LCD. I then have them bring up their histogram and there’s a mountain of pixels pushed up to the left edge. The result is lost shadow detail.
Lost Shadow Detail: Lost shadow detail results in blocked up areas that reveal little or no subject information. If the RAW capture does have some pixel detail embedded, bringing it out with software results in noisy dark areas. Granted, the use of noise reduction software helps rescue the image, but I have better things to do than sit in front of a computer for added hours. Additionally, too much underexposure muddies up the colors. If captured properly, much more saturation would be revealed. The most common culprit that causes underexposure is areas of brightness that fool the meter into thinking there’s too much light which results in an overly dark photo.
Lost Highlight Detail: Lost highlight detail results in glaring areas of pure white that show no texture, form, shape or detail. This results in areas of distractions that leave the viewer wanting to know what the image would look like if the photo was properly exposed. Additionally, the color is muted as it strips the pixels of their color reproducing potential. The most common culprit that causes overexposure is areas of darkness that fool the meter into thinking there’s too little light which results in highlights that are blown out.
Use the Histogram: If you’re one of the guilty who use the LCD to evaluate exposure, learn to use the histogram instead.
a) If the majority of pixels are biased to the left and there’s a mountain touching its edge, the image will suffer from underexposure. Dial in PLUS compensation and retake the image. Check the histogram again. Keep dialing in more exposure until the distribution of pixels is spread out more to the right. The one aspect to keep in mind that’s extremely important is to watch what’s happening to the right side of it as you add to the exposure. Should a spike of pixels appear to the far right, stop adding compensation as you’ll begin to blow out the detail in the whites. If this is the case, it’s an indication that the tonal range of the image exceeds what a single capture is able to reproduce.
b) If the majority of pixels are biased to the right and there’s a mountain touching its edge, the image will suffer from overexposure. Dial in MINUS compensation and retake the image. Check the histogram again. Keep dialing in less exposure until the distribution of pixels is spread out more to the left. The one aspect to keep in mind that’s extremely important is to watch what’s happening to the left side of it as you take away from the exposure. Should a spike of pixels appear to the far left side, stop subtracting compensation as you’ll begin to block up detail in the shadows. If this is the case, it’s an indication that the tonal range of the image exceeds what a single capture is able to reproduce.
Memorize how the light falls on the subjects in each of the above situations and make a connection as to how much PLUS or MINUS compensation you dialed in. Keep this information in the back of your mind and the next time you encounter something similar, you’ll realize it calls for an adjustment that allows you to create the best possible digital exposure.