[KPhotoAlbum] Numbers - Re: "F Number" vs. "Aperture Value"

Mon Dec 2 22:47:35 GMT 2019

As an addendum, here is a rough translation table based on my exif database. 
Taking a closer look at the invalid values reveals that not all cameras store 
the APEX value at all:

sqlite> select count(*) from exif;
30492
sqlite> select count(*) from exif where Exif_Photo_ApertureValue < 0.1;
24395
sqlite> select count(*) from exif where Exif_Photo_FNumber < 0.1;
4135

sqlite> select Exif_Photo_ApertureValue, Exif_Photo_FNumber from exif group by 
Exif_Photo_ApertureValue order by Exif_Photo_ApertureValue;
-2147483648.0|0.0
-1.0|-1.0
0.970854|1.4
1.0|1.4
1.356144|1.6
1.53|1.7
1.531069|1.7
1.695994|1.8
1.85|1.9
1.851998|1.8999
2.0|2.0
2.2|-1.0
2.27|2.2
2.275007|2.2
2.27500704754745|2.2
2.27500712453691|2.2
2.27500720668781|2.2
2.28|2.2
2.375|2.2
2.52|2.4
2.52606882168926|2.4
2.625|2.5
2.643856|2.5
2.64385628700256|2.5
2.663|2.663
2.75|2.6
2.76|2.6
2.8|-1.0
2.81|2.65
2.86|2.7
2.96875|2.8
2.97|2.8
2.97085357390701|2.8
2.97085380554199|2.79999995231628
2.970854|2.8
3.0|2.8
3.3|3.2
3.34375|3.2
3.35614371299744|3.20000004768372
3.356144|3.2
3.375|3.2
3.4|3.3
3.5|3.4
3.53125|3.4
3.6|3.6
3.6147096157074|3.5
3.61471|3.5
3.61471557617187|3.5
3.625|3.5
3.7|3.6
3.8|3.7
3.9|3.8
4.0|4.0
4.1|4.2
4.3|4.5
4.33984375|4.5
4.339844|4.5
4.33984994888306|4.5
4.33985|4.5
4.34375|4.5
4.375|4.5
4.4|4.6
4.5|4.8
4.52|4.8
4.53125|4.8
4.6|5.0
4.625|5.0
4.643856|5.0
4.64385604858398|5.0
4.64385986328125|5.0
4.65625|5.0
4.9|5.5
4.90625|5.5
4.96875|5.6
4.97085380554199|5.59999990463257
4.970854|5.6
4.97085571289062|5.6
5.0|5.6
5.3|6.2
5.31069946289062|6.3
5.310704|6.3
5.3125|6.3
5.375|6.3
5.4|6.4
5.5|6.8
5.6|7.1
5.625|7.1
5.655638|7.1
5.6556396484375|7.1
5.7|7.1
5.8|7.4
5.9|8.0
6.0|8.0
6.2|8.6
6.33984375|9.0
6.33985|9.0
6.375|9.0
6.4|9.1
6.5|9.6
6.625|10.0
6.64385986328125|10.0
6.91886901855469|11.0
7.0|11.0
7.375|13.0
7.40087890625|13.0
7.400879|13.0
7.61471557617187|14.0
7.625|14.0
8.0|16.0
8.33984375|18.0
8.375|18.0
8.625|20.0
8.64385986328125|20.0
8.918863|22.0
9.0|22.0

Am Montag, 2. Dezember 2019, 23:32:30 CET schrieb Johannes Zarl-Zierl:
> Hi,
> 
> Forgive me my technical illiteracy - I didn't realize that there are two
> almost identical measures at play here.
> 
> The value called "Aperture Value" in the UI corresponds to
> Exif.Photo.ApertureValue, which is the APEX[1] value.
> The value called "F Number" is Exif.Photo.FNumber, which is the focal ratio
> as commonly used.
> 
> For better clarity, I propose we relabel the first entry to "Aperture Value
> (APEX)" and the second one to "Aperture Value (F Number)".
> 
> >From what I've read about APEX though, I conclude that the APEX aperture
> >value
> should have different values, i.e. the range is probably incorrect.
> 
> Cheers,
>   Johannes
> 
> 
> 
> [1] https://de.wikipedia.org/wiki/Additive_System_of_Photographic_Exposure
> 
> Am Sonntag, 1. Dezember 2019, 02:49:26 CET schrieb Johannes Zarl-Zierl:
> > Hi Robert,
> > 
> > Am Samstag, 30. November 2019, 03:41:28 CET schrieb Robert Krawitz:
> > > Why are there two separate controls in the search dialog?  They mean
> > > the same thing (but don't have the same effect -- one finds zero
> > > matches while the other finds the correct matches).
> > 
> > That's an interesting question. A casual glance at the source code doesn't
> > help, unfortunately: apparently both the aperture and the f-number were
> > added within a short amount of time (33cfb31cf vs 803e77395).
> > 
> > My best guess is that fnumber was first renamed to aperture, and then a
> > mistake was made when applying some patch, reintroducing fnumber...
> > 
> >   Johannes
> > 
> > _______________________________________________
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