# Talk:APEX system

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## Redundant?

Does anyone else find 'APEX system' (Additive system for Photographic EXposure system) redundant?

I think much of the material on exposure value should go in the entry for that topic. Perhaps most of the discussion of the exposure equation should be in a separate entry for that topic.

I removed the reference to "light value" because the term has had so many different meanings that it essentially is meaningless; I added all credible meanings of which I am aware to the entry for light value.

Any discussion of APEX is necessarily historical—although the concept was technically interesting, APEX essentially was stillborn. I'm still not completely sure when the use of past (vs. present) tense is appropriate.

JeffConrad 08:03, 19 July 2006 (UTC)

## Edits of 19 October 2006

There appears to be a bit of a conflict in EXIF 2.2 among $K$, $N$, and the stated value of $B$ for Bv = 0; no manufacturer that I know of currently uses $K$ = 10.7. The standard doesn't explicitly state that $N$ = 1/3.125, but the implication is strong. I've speculated that it may be due to rounding, but it may just be sloppy copy editing (it seems strange to state that $B$ is in cd/m^2 yet give the example in footlamberts). The description of the APEX quantities in general is pretty cryptic; it also seems strange not to state or even give guidance on the constants $K$ and $N$.

I've tried to simplify the EXIF section (do we really care whether the data are recorded as rational numbers or unsigned short ints?). I changed the formula to force TeX because the HTML rendering has the annoying habit of appending hyphens to some $. . .$ sequences. I also moved the EXIF link to the References section for consistency with the other references.

The last paragraph in the EXIF section still needs work. JeffConrad 10:16, 19 October 2006 (UTC)

Reading the EXIF 2.2 specification yet again, it would appear that Bv and Sv are quantity symbols that weren't properly typeset, so I have changed them accordingly. Because the Use of APEX values in EXIF section isn't strict homage to APEX, I have followed ISO 31-0 and used upright type for the descriptive subscript v. The seemingly redundant extra curly braces were added to inhibit the dreaded appended hyphen. JeffConrad 02:51, 20 October 2006 (UTC)