How do I choose aperture, shutter speed, and ISO for the lowest-noise image?
Asked 10/6/2017
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I’m photographing a dim, mostly static subject. If I keep the aperture fixed, an image shot at ISO 1600 and 1/125 s looks cleaner than one shot at ISO 3200 and 1/250 s, even though both are equally exposed. That makes sense because the lower-ISO shot gathered more light and needed less amplification.
So in practice, how do I decide the minimum amount of light I need for a low-noise result? If the scene and camera are unchanged, and I’m only trading ISO against shutter speed or aperture, is there a general rule for choosing settings without having to shoot lots of test frames?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
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Define 'low noise'... In general (disregarding long exposure noise) the lower the ISO setting, the lower the noise. In your case, with a stable camera and a non-moving subject I'd suggest setting the ISO to its default (100 or 200), setting aperture for desired DOF, and adjusting the shutter speed for a proper exposure according to the camera's light meter.
In your case, you would want to leave your aperture where it is, reduce your ISO to 100 (for example) which is 4 stops lower than 1600, and reduce your shutter speed to 1/8 of a second- 4 stops lower than 1/125.
Originally by user11772. Source · Licensed CC BY-SA 4.0
user11772
8y ago
0
Generated from our catalog & community — verify before relying on it.
General rule: for the same final exposure, use the lowest ISO you can while still getting the shot you want. Lower ISO usually means less visible noise.
A practical workflow is:
- Set aperture for the depth of field you want.
- Set the slowest shutter speed you can get away with for the subject and camera stability.
- If the subject and camera are still, use a tripod/remote and go much slower.
- If there’s motion, choose a shutter speed fast enough to stop it.
- Then use the camera meter to get proper exposure, raising ISO only as much as needed.
So for a static subject on a tripod, ISO 100 or 200 with a longer shutter is usually cleaner than ISO 1600 or 3200 with a shorter shutter. There isn’t a single universal “minimum light” threshold for low noise, because it depends on what you consider acceptable noise and whether motion blur or long-exposure effects become a problem.
If your camera has Auto ISO, you can set aperture and minimum shutter speed first, and let the camera choose the lowest ISO that gives proper exposure.
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