AFInfo Tags for Pentax K3-iii

[ulrichk7]

HI,

found some infos about the tag here .
This seems to be what is used by the K3-iii (the AFPointsInFocus is empty), but some of the info is not relevant for K3-iii(?)

I wonder, if it is possible to get the points in focus and to assign them to one of the 101(!) AF points of the camera.
The camera knows this  see attachment - foto of the LCD monitor and the red-dot mark of the point in focus (Autofocus_sample.jpg).

My 'project' is to show this on the PC. Therefor I extract the (smaller) jpg from the DNG by
exiftool -b -W %d%f_AF.%s -copy0:previewimage -PreviewImage picture.DNG

An then fade it and compose with a prepared png of all AF points by
convert picture_AF.jpg -fill white -colorize 50% AF_points.png -gravity center -composite picture_with_AF_points.jpg

This works quite well and results in the second attachment (picture_with_AFpoints.jpg).

While this was the easy part, the question is now how to get the points in focus from the EXIF AFInfo and color them in red in the output?

exiftool -U -s '-Pentax_AFInfo*' picture.DNG
gives me 4976 lines of output.

I could prepare some sample DNG or need advice how to proceed.
Thank you in advance

Ulrich

[StarGeek]

Unfortunately, most camera companies do not document their MakerNotes. What is known of the MakerNotes has only been found by people testing things out by taking a photo, changing a setting, taking another photo, compare what has changed, etc.

It's quite probable that nobody knows what all that data means. Two of the tags listed under AFInfo literally have "Unknown" in their name.

So there's not much help to be offered. With thousands of lines of data, it seems like a huge task that nobody has felt it was worth the time needed to decode it, especially since camera companies are constantly changing formats and the results might not be transferable to other models.

[ulrichk7]

Thank you StarGeek for the quick reply.
Yes, I was afraid of that. 4976 is a bit too much for trial and error.
I also read somewhere that the meaning might change in different firmware versions.
So I guess I will live with the two easy steps and - in case - do the coloring manually according to the LCD info.

Ulrich

[Phil Harvey]

This shouldn't be too hard to find.  If more than 1 AF point may be active at the same time, then the 101 AF points may be represented by the bits in 13 bytes.  But presumably there is also a primary AF point that may be represented by a single byte.  If you can shoot a series of 8 images I may be able to figure it out.  If we number the AF rows by letter A-I and the columns 1-13, then samples with AF points in this sequence would be good: A1,A2,A3,A13,B1,B2,E7(center),I13.  (For reference the picture you posted uses A11.)  You can email the samples to me: philharvey66 at gmail.com

- Phil