Nidelva river through Trondheim Norway

Nidelva river through Trondheim Norway
by Saaru Lindestokke                

Submit your Photo
Hall of Fame

Please participate in Meta
and help us grow.
Photography Stack Exchange is a question and answer site for professional, enthusiast and amateur photographers. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

A photo shot with an 1:1.8 lens contains the following exif data:

ApertureValue: 1695994/1000000  
MaxApertureValue: 16/10

How is this possible? Both values are <1.8.

share|improve this question
What is writing that value? EXIF data is just metadata appended to an image file, and is editable by many programs and devices. – drewbenn Jan 13 '12 at 17:46
OT, but I was curious so I just looked it up: I now believe that the proper capitalization is "Exif" which is how it is used throughout the standard. – drewbenn Jan 13 '12 at 18:29
up vote 5 down vote accepted

You are confused because ApertureValue and MaxApertureValue are APEX values, not F-stops.

An F-stop of 1.8 is equivalent to an APEX aperture value of about 1.695994. (The formula is Av=log₂A², where Av is ApertureValue and A is f-number. See the Wikipedia APEX system page for a full explanation.)

Some exif readers (like ExifTool) convert these to F-stops for the user, but others do not.

share|improve this answer
Woah! I can't believe I didn't realize that. That's crazy but indeed seems to be correct. See EXIF standard here. – mattdm Mar 12 '15 at 18:52
According to the ExifTool docs, FNumber and ExposureTime correspond to the values we're used to working with, and ApertureValue and ShutterSpeedValue are the APEX values. – mattdm Mar 12 '15 at 19:00
FWIW, my Pentax camera doesn't seem to set the APEX tags at all. My Nexus phone does, however. Both ExifTool and Exiv2 convert ApertueValue to f/number for display (in this case, f/2.4), but if I look at the raw values, Fnumber is set to 240/100 and ApertureValue to 252/100 — the corresponding APEX value. Hmmm. I'm not sure if these tools are making it more or less confusing by converting. – mattdm Mar 12 '15 at 19:10

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.