Sun elevation angle is how high the sun sits above the horizon at a given moment, measured in degrees from 0° (on the horizon) to 90° (directly overhead).
Sun elevation angle is how high the sun sits above the horizon, from 0 degrees at the horizon to 90 straight overhead, and it controls two things photographers care about: shadow length and light quality. Below about 10 degrees the light is warm, soft-edged and directional, with shadows several times longer than the objects casting them. Above about 50 degrees the light turns hard and colourless and shadows collapse to almost nothing.
Knowing the number for a given time lets a photographer predict what the light will do before leaving home. A portrait planned for a 15-degree sun has flattering side light; the same shoot two hours later at 40 degrees needs a diffuser or open shade to be usable. Elevation also caps how high the sun gets at all, which in winter at high latitudes may never pass 15 degrees the whole day.
At a sun elevation of 5 degrees, roughly twenty minutes after sunrise, a standing person casts a shadow about eleven times their height, long enough to stretch a subject's silhouette right across a beach. At 20 degrees, mid-morning, that shadow drops to under three times their height. At 60 degrees, near midday in summer, it shrinks to about half their height and points nearly straight down.
A landscape photographer using this schedules a shoot of rippled sand dunes for when the sun sits between 5 and 15 degrees, because that is the band where the ripples throw visible shadows and read as three-dimensional. By the time the sun reaches 30 degrees the same dunes look flat and featureless in the frame, whatever the aperture. Checking the elevation figure the night before turns a pre-dawn alarm into a decision rather than a gamble on what the light will be doing.
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