Focus Distance 2

[RT--]

I looked at the "Focus Distance 2" data of some long shots from the last couple of days.
440m real = 1240m fd2
620m real = 1670m fd2

For very close distance it seems to be ok but beyond 50m or so it really falls apart.
Where does the Focus Distance 2 come from?

[greybeard]

Do you have some examples? Are these images from Sony cameras?

[Phil Harvey]

One should keep in mind that longer focus distances with short lenses will be wildly inaccurate.  In general, camera focus distance measurements are only approximate to begin with.

- Phil

[capricorn]

The focus point plug-in which I have just released as a major update also displays AF relevant tags like focus information.

When implementing this part for Sony, I learned there is no "focus distance" tag by Sony. One reference I found said that "Focus Distance 2 is the result of an erroneous user supplied formula to exiftool".

So I was hesitating when a plug-in user requested me to add this tag. I asked him for a thorough review regarding the usefulness of this information. His answer was:

Ok, I did the test.
The same object with four different focus length: 24mm - 105mm - 200mm - 600mm.
The results: 3.6m - 139m - 35m - 30m :-((

You're right, this doesn't any sense.

Which is in line with Phil's statement.