 Shelly Blake |
Difference between FNumber and ApertureValue? I was looking at photos of Des Moines, IA and it gave various info about the pic. It gives an FNumber and an ApertureValue (i.e. FNumber= f9; ApertureValue= f6). Exposure time is 10/64s (I've never seen exposure time read this way before). Can you explain all this to me, in particular the difference between the FNumber and the ApertureValue? You can look at the site I am referring to at: http://www.knowdowntown.com/gallery/albums/2/14.phpx Thanks! ~Shelly
|
|
|
|
||
|
Jon Close |
There is some error or confusion in the labeling of some of those pictures. The one you linked - if you click on "View Original" and then check the EXIF data (if you have an EXIF viewer) you'll see that the shutter speed (Exposure Time) was 1/800 and the aperture was f/9. Also embedded in the EXIF are those settings given in terms of APEX units (Additive system of Photographic EXposure). In APEX, Aperture Value = 2 x LOG(FNumber), in base 2. So for f/9 the corresponding Aperture Value is 6.3399 (rounded to 6 in this case). Similarly, Shutter Speed Value = - LOG(exposure time), in base 2. For 1/800 the Shutter Speed Value is 9.6439, rounded to 10. I don't know why it is given as a fraction 10/64. APEX units simplify things for programming a camera's metering algorithms, and digital image capture. It allows expressing an Exposure Value as the sum of the Aperture Value and Shutter Speed Value.
|
|
|
|
||
|
Kerry L. Walker |
OK
|
|
|
|
||
|
Shelly Blake |
Clear as mud. :O) Thank yous for the response. I probably need to let that info sink in and do a little bit of research. THANKS!
|
|
|
|
||
|
This old forum is now archived. Use improved Forum here
Report this Thread |
||