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A2/6 What are LV and EV
Introduction
LV, Light Value and EV, Exposure Value, are terms used to allow easy discussion of
exposure and light without the confusion of the many equivalent combinations
shutter speeds and apertures.
LV refers to how bright the subject is. EV is the exposure setting on the camera.
You may have seen them if you like to read the fine print of camera specifications.
They are used to specify ranges of light levels for metering and autofocus.
EV and LV follow an open-ended scale. Each one is one stop away from the next. In
photography values of about 0 to 18 are commonly used. Negative values are
perfectly valid, just very dark and only occur in night photography. LV 15 is full
daylight, for example.
Each Exposure Value, or EV, represents any of many different but equivalent
combinations of f/stop and shutter speed. For instance, 1/250 at f/8 is EV14, and so
is 1/125 at f/11. 1/125 at f/8, one stop more exposure, is EV13, and 1/250 at f/11, one
stop less exposure, is EV15. You don't need to remember these, they are on the dial of
your exposure meter.
Understanding them will allow you to recognize common lighting values and guess
correctly at exposures even without a meter.
This system is the correct way to discuss photographic light and exposure because it
avoids all the confusion of f/stops and shutter speeds, if all you really want to discuss
is light and exposure levels. it replaces the idiotic question I get all the time while
shooting, "what f/stop are you using," which of course means nothing by itself.
LV, or Light Values
An LV, or Light Value, is a number that represents how bright a subject appears in
absolute terms. It does not take film speeds or exposure into account. LVs are very
handy photographic terms to use to describe lighting levels.
LVs measure light coming from a subject, or "luminance." They are not a measure of
how much light is falling on a subject. In other words, the same light falling on a
black object will have a lower LV than the same light falling on a white object.
Some light meters, especially spot meters like the wonderful Pentax Digital
Spotmeter and analog Pentax Spotmeter V, read directly in LV. You transfer this
number to a dial that, along with your film speed, reads out all the combinations of
aperture and shutter speed that will give the correct exposure.
Here's a table of common Light Values associated with common situations. If you
use one of the Pentax meters you will quickly start to learn these without even
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