Second Photography Basics tutorial from the series! (intro and index here).
Exposure time, or shutter speed, is the amount of time the shutter remains open, to let light into the film or sensor of your camera. If you already know exposure you might want to skip to the animation showing everything #INaGIF, if you want to know what we’re talking about, go on reading
That’s easy! This of course will determine the global brightness of the picture, but it will also define more or less the captured moving objects. If you want a very defined and sharp moving object, it’s better to have a fast shutter (short exposure), while if you’re only portraying still objects, or if you’re aiming for a creative effect, you can use a slower shutter.
Here you can see a fan series with different values (the right part of the images is corrected as always, to make things more visible).
The unit of measure is seconds, so the above examples range from 0.5 seconds to 1/4000th of a second.
Also in this series I changed a single setting ONLY (exposure), you can see things getting very dark or very bright pretty fast. In a future series I will use all settings to give a comprehensive example.
To have good result with a handheld camera and slow moving or still objects a good common setting is around 1/60 or 1/80. A general rule is to have the speed corresponding to your lens’ focal length reciprocal, so 1/50 for a 50mm, 1/300 for a 300mm and so on. This can vary depending on how steady you hand is, how you handle your camera, your position, camera and lens weight, your heart rate, etc. For example, snipers breathing techniques can help a lot with relatively long exposures or “long” lenses.
A short or fast exposure corresponds to a fast shutter, that’s less time it stays open, to summarize this part, here’s an animated recap*:
Fast Exposure Time<-> Less Light Captured <-> “Freezed” movements
Long Exposure Time <-> More Light Captured <-> Objects Trails
Taking pictures with a slower shutter requires usually a tripod or some sort of decent camera support. Of course, that’s if you want your subjects focused and defined, experimenting with long exposures while moving the camera around could be pretty interesting….
It’s possible to reach extreme results with specific accessories, to capture, for example, the movement of the stars as a trail, or a bullet in mid-air, as if freezed.
More info on Exposure Time on Wikipedia.
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*As always, #INaGIF animations are conceptual and serve the purpose of explaing a behavior, some aspects are exaggerated or reduced to clearly show the fundamental notions.