Film speed converter
Convert film speed between ISO and the German DIN degrees, and see how many stops apart two speeds are.
That's about the same as general-purpose film. That is 2 stops from ISO 100.
What it means
How sensitive is that?
Digital cameras quote an ISO-equivalent sensitivity. Above the base ISO the sensor is not more sensitive, only amplified — which is where the noise comes from.
Every unit
Your speed in every unit
Learn
Three things worth knowing
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Every 3 DIN is one stop
ISO 100 = 21 DIN, ISO 200 = 24, ISO 400 = 27. Doubling the arithmetic number adds three to the logarithmic one.
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ASA became ISO
The American ASA scale and the German DIN scale merged into ISO in 1974, which is why the numbers on a modern box are just the old ASA figures.
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Higher ISO is not free
Each doubling buys a stop of light and costs noise. On film it costs grain; on a sensor it costs shadow detail, because the signal is being amplified rather than collected.
Shortcuts
Popular speed conversions
Background
About ISO and DIN
ISO doubles as the film gets twice as sensitive: 100, 200, 400, 800. DIN is logarithmic, adding three degrees for each doubling, so ISO 100 is 21° and ISO 400 is 27°.
Old film boxes carried both, printed as 400/27°, which is why the ISO standard number still has two halves.