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I'm working on image processing software (mind that I'm a programmer and when talking about photography, I'm "tabula almost rasa").

In this software, I'm using a RAW decoder that returns a data representation of the image that I can work on. With it I also get a lot of metadata. I need to use and display some of these metadata values, but the problem is I need to display them rounded to common values. For example the data I get from the image are:

Aperture: 14.05 (not sure about rounding here)

ISO: 200 (nothing wrong here :))

shutter: 0.0101316 (approx. 1/98, which means it should be rounded to 1/100 )

Now what I need are some "complete" (as complete as possible) tables for common aperture and shutter speed values.

(You know, when the shutter speed is 1/99, you automatically round it to 1/100, when it's 1/7800 you round it to 1/8000.

I don't care about stops and other things since I can't so anything about them, I only need a table of shutter speeds/apertures, so I can round the values I get to them).

Something like:

when photographers talk, the shutter speeds they expect are:

15 8 4 2 1 1/2 1/ 1/8 1/15 1/30 1/50 1/60 1/100 ...... 1/3000....1/8000

common apertures are:

...1 2 3 4 5 6.... 14 16....

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  • \$\begingroup\$ And the aperture stops are covered at photo.stackexchange.com/questions/594/what-does-f-stop-mean \$\endgroup\$
    – mattdm
    Aug 18, 2014 at 13:39
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    \$\begingroup\$ Also, you say that "you don't care about stops and other things"... This makes me strongly feel that you need to step back and learn lot more about the basic terminology of the field your program is meant to be used in before working any further on the user interaction design. That's because the things you are looking for in this question are the stops. If you don't have basic concepts like that down, what else are you fundamentally missing that might perplex your users? \$\endgroup\$
    – mattdm
    Aug 18, 2014 at 13:42
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    \$\begingroup\$ It's worth pointing out that common apertures and shutter speeds aren't the only ones that can be used. Electronic shutters mean 1/99 sec is possible and perhaps entirely correct; a non-standard aperture of f4.1 might be more accurate than the f4 value printed on the lens, too. In other words, why do you need to round them? \$\endgroup\$ Aug 18, 2014 at 14:38
  • \$\begingroup\$ My A77 Sony offers 2 steps or 3 steps between standard power-of-two speed and aperture values. Others may offer more. You may wish to give users the ability to set the effective number of inter-stop steps which will affect the rounding. \$\endgroup\$ Aug 18, 2014 at 15:23

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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.

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