Why are 1/125s and 1/30s commonly mentioned shutter speeds?
Asked 3/19/2015
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My teacher highlighted 1/125 second and 1/30 second as important shutter speeds. Is there any special significance to those two values, or are they just examples from the normal shutter-speed scale?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
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I understand that you mention those two specific speeds for some reason, and not as a general example.
My best guess on why your teacher is asking is:
Traditionally 1/125 was the maximum shutter speed to sync a flash, because higher velocities were achieved by starting to close the shutter before it has finished "opening", so a flash would only expose a fraction of the frame.
Now a common velocity for this is 1/180 - 1/250.
The 1/30 is probably considered the minimum velocity on which a photographer can hold a camera by hand and not take a shaky photo. This minimum speed depends on the photographer's skill, the focal length, the sensor size, and whether the camera or lens has a stabilizer integrated.
This 1/30 probably refers to a 50mm equivalent lens.
Originally by user37321. Source · Licensed CC BY-SA 4.0
user37321
11y ago
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Generated from our catalog & community — verify before relying on it.
These speeds aren’t magically special on their own, but they’re commonly mentioned for a few practical reasons:
- They’re standard full-stop shutter speeds. Going from 1/125s to 1/30s is a 2-stop change, so 1/30s lets in 4× more light than 1/125s, assuming aperture and ISO stay the same.
- 1/125s was historically a common maximum flash sync speed on many cameras. Faster shutter speeds could cause part of the frame to be blocked during a flash exposure. On many modern cameras, sync speed is often around 1/180s to 1/250s instead.
- 1/30s is often treated as a rough lower limit for handholding without camera shake, especially with a “normal” lens (around 50mm equivalent). In practice, the safe minimum depends on focal length, sensor size, image stabilization, and the photographer’s steadiness.
So your teacher may have been referring to these traditional rules of thumb, not to any universal law that makes those exact numbers uniquely important.
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