How should I round aperture and shutter speed metadata to standard photographic values?
Asked 8/18/2014
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I'm processing RAW image metadata in software and need to display exposure settings using the standard values photographers expect, rather than exact numeric values from the file. For example, shutter time might come in as 0.0101316 seconds, which should display as about 1/100 s, and an aperture value might come in slightly off from a marked setting.
Is there a standard table or convention for common shutter speed and aperture values? I’m mainly looking for the usual full-stop, half-stop, and third-stop series so I can round metadata to the nearest standard photographic value.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
1
You can get more data about how these rounded values were derived here.
The page contains a table called "Tables for Aperture F/stop, ISO, Shutter Speed Values - in Full, Third and Half stops" - because steps and rounding is different based on whether you are using 1/1, 1/2 or 1/3-stop resolution.
Originally by user24785. Source · Licensed CC BY-SA 4.0
user24785
11y ago
0
Generated from our catalog & community — verify before relying on it.
Yes. The standard way to round these values is to use the normal photographic exposure series rather than arbitrary whole numbers.
For both shutter speeds and apertures, the available marked values depend on whether the camera uses full-stop, half-stop, or third-stop increments, so your rounding should be based on one of those standard tables.
Typical examples are:
- Shutter: … 1/60, 1/80, 1/100, 1/125, 1/160 …
- Aperture: … f/8, f/9, f/10, f/11, f/13, f/14, f/16 …
So a value like 0.0101316 s would reasonably round to 1/100 s if you’re using the standard series. Likewise, aperture values should be rounded to the nearest standard f-stop in the chosen increment set.
In short: use a reference table of full-, half-, or third-stop values for aperture, ISO, and shutter speed, and round to the nearest entry in that table. That is the convention photographers expect.
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