 James R. Beatty |
zeroing out your camera I am a long time amature photographer, looking at getting better and perhaps entering contests, part time business, etc. In other words, looking at ways to improve. I'm taking a basic lighting class in hopes of, again, improving. The term "zeroing out your camera" came up in class. I asked the instructor to explain and he basically said when you meter with your camera, you need to be sure you're not at a - or + setting, it should be on a 0 setting; zeroing out your camera. As not to delay the class with further discusson, I let it pass thinking I could find an explanation in my many photography books. None of them make mention of this term. Can someone help explain it.
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Jon Close |
Many cameras have a control for exposure compensation, usually ranging from -2..-1..0..1..2 in 1/2 or 1/3 stop steps. At 0, the exposure is set as determined by the meter. I believe this is what your instructor wants you to check. The meter is calibrated to give the correct exposure for light reflected from an 18% gray tone, which corresponds to the average reading in a typical scene of many tones/colors. But where the scene has a large amount of white or light tones (eg. wedding dress, white sand beach, snow,...) the reflected light will seem brighter to the meter than it actually is, and the meter will tend to underexpose. So you would compensate by dialing in + exposure compensation. Similar with black or dark-toned subjects. The meter will tend to overexpose, so you'd dial in - exposure compensation.
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James R. Beatty |
Thanks Jon, but I have to admit I'm still a little confused, or maybe just thick. What ever the camera meter reads would be considered 0, right? So, if the object in question was light or white in color, I should use + exposure compensation, and if dark or black I'd use - exposure compensation, correct? I assume you need to experiment with how much + or - compensation based on the object. Thanks much for the quick response. Jim
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Jon Close |
The basic meter reading is 0, and any exposure compensation you set is applied to that. Example: In aperture-priority mode set f/8 and EC to 0. Frame the scene in the viewfinder as you want it, half press the shutter button to meter, and let's say it determines the shutter speed to be 1/250. Without changing anything else, if you set -1 EC then meter, you'll get 1/500 (1 stop less exposure than what the meter read). If you set +1 EC, the shutter speed will be 1/125 (1 stop more exposure). The technically correct exposure needed is dependent on the amount of light falling on the subject. This can be measured with a separate incident light meter placed next to the subject. Generally, an incident light reading needs no exposure compensation. The meter built into cameras however can only measure light reflected off the subject/scene back to the camera. The intensity of the reflected light varies with the tone of the subject. In most situations you don't need to apply any exposure compensation, ie. you can leave it set to 0. Most color print films are very forgiving of exposure "errors" up to several stops, and the multisegment averaging meters in modern cameras ("Evaluative" in Canon, "Matrix" in Nikon, "Honeycomb Patterned" in Minolta, etc.) include algorithms that automatically apply their own exposure compensation in certain situations. Applying EC is more appropiate shooting slide film (which has very narrow exposure latitude), spot metering on individual elements of a scene, or varying the exposure from what is "technically correct" for artistic/editorial reasons.
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James R. Beatty |
Thanks again, Jon. Your expalnation was clear and made sense. Now I'll go practive. Jim
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