Why does an equivalent exposure table differ from the Sunny 16 rule?
Asked 11/24/2015
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I found a shutter speed/aperture table in a photography book showing combinations like f/16 at 1/50s, f/11 at 1/100s, f/8 at 1/200s, etc., all giving the same exposure. But the Sunny 16 rule says that in bright sun, at ISO 100, correct exposure is about f/16 at 1/100s (or the nearest available shutter speed).
Why do these disagree? Is one of them wrong, or is the table only showing relative equivalent exposures rather than exposure for a specific lighting condition?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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The quote from the book does not state that the numbers are intended for any specific lighting situation, so it appears to be indeed only concerned with showing how aperture and shutter speed can vary while maintaining the same exposure.
And anyway, the "Sunny 16" rule is only a broad rule of thumb and one f-stop difference is not that big. Maybe the author of the book simply looked at his camera on a slightly overcast day rather than a sunny one.
Originally by user25699. Source · Licensed CC BY-SA 4.0
user25699
10y ago
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Generated from our catalog & community — verify before relying on it.
Both can be correct because they describe different things.
The table is an equivalent exposure chart: it shows combinations of shutter speed and aperture that let in the same total amount of light. For example, opening the aperture by one stop and using a shutter speed one stop faster keeps exposure the same.
By itself, that table does not tell you what lighting it is for. It could represent any scene brightness.
The Sunny 16 rule is different: it is a rule of thumb for a specific lighting condition—bright midday sun. At ISO 100, it suggests about f/16 at 1/100s, or the nearest shutter speed your camera has, often 1/125s.
So f/16 at 1/50s in the table is not contradicting Sunny 16; it just represents a different baseline exposure, about one stop brighter than Sunny 16. That difference is not huge, and real-world exposure also has some tolerance.
So yes: the table is about relative equivalence, while Sunny 16 is about estimating exposure in a specific kind of light.
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