Why do some EXIF exposure values appear as odd fractions like 10/4000 or 301/100000?
Asked 6/29/2013
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Sometimes an EXIF viewer shows exposure values as fractions such as 10/4000 or 301/100000 instead of a simple shutter speed like 1/400 s. What do these values mean? Are they EXIF read/write errors, or just another way of storing the actual exposure time?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
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The values are just fraction. Depending on the camera, you see odd rounding but they do correspond to reality as far as I have seen. You will see the same type of rounding in the EC or exposure bias fields.
10/4000 = 1/400s which is a moderately fast shutter-speed and 301/100000 = approximately 3/1000 = about 1/300 which is just a tiny bit slower. You will often see other extremes such as 30000/1000 = 30s on the long side of exposure.
In my experience, compact cameras tend to produce stranger output particularly because they can use shutter-speeds and ISO values in odd fraction and not the usual 1, 1/2 or 1/3 stops.
Originally by user1620. Source · Licensed CC BY-SA 4.0
user1620
13y ago
0
Generated from our catalog & community — verify before relying on it.
These are usually just the raw fractional values stored in EXIF, not errors.
EXIF often records exposure time as a rational number (numerator/denominator). Some software displays that raw fraction instead of simplifying it into a familiar shutter speed.
Examples:
- 10/4000 = 1/400 s
- 301/100000 = 0.00301 s, which is about 1/332 s, often rounded and described as roughly 1/300 s
- 30000/1000 = 30 s
So 301/100000 is not necessarily wrong—it just represents a very specific measured or selected shutter time. Some cameras, especially compacts, may use less conventional increments rather than standard full-, half-, or third-stop values, so the fractions can look unusual.
You may see similar raw rational values in other EXIF fields too, such as exposure compensation.
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