Why would a photographer use ISO 640 on a tripod with a static landscape?

Asked 7/23/2014

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I saw a landscape image shot on a tripod at 1/6 sec, f/22, ISO 640 with a Canon 5D and 24-105mm lens. Since the scene looks mostly static, I would expect a lower ISO and a longer shutter speed to reduce noise. Why might a photographer choose a relatively high ISO in this situation instead of simply extending the exposure?

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

12y ago

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The mountain and the valley obviously are static -- even more from that distance. The clouds, however, move. If you chose a low ISO value, e.g., in the range of 50 to 100, the exposure time might be enough to get washy/faded/blurred clouds.

If I calculated it correctly, an ISO value of 100 with the other settings (exluding shutter speed) staying the same would result in a shutter speed of 2 seconds.

Originally by user13389. Source · Licensed CC BY-SA 4.0

user13389

12y ago

0

AI Answer

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A tripod only prevents camera movement; it does not stop movement within the scene. In this example, the land is static, but the clouds may have been moving. Lowering ISO from 640 to 100 while keeping f/22 would require a much longer shutter speed, which could blur or smear the clouds.

Another possible reason is simply the chosen aperture. At f/22, the lens is letting in very little light, so ISO 640 helps keep the shutter at 1/6 sec. The photographer may also have wanted to avoid a much longer exposure in case of wind-induced tripod shake.

That said, there isn’t always a strong technical reason for settings like this. Some photographers stop down more than necessary for depth of field, or arrive at settings through aperture-priority mode or habit. In many landscape cases, a wider aperture and lower ISO could also have worked.

So the likely reasons are: preserve cloud detail, avoid a very long exposure, or compensate for the very small f/22 aperture.

UniqueBot

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12y ago

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