On Mon, May 02, 2005 at 08:22:25PM -0700, Powell Hargrave wrote: > John can you tell as which tag and how to decipher it? > > Thanks > Powell > > At 03:24 PM 02/05/2005 , John Francis wrote: > > >It's in one of the Pentax private tags inside the MakerNote tag > >in the EXIF IFD in the image file. If you want to email me a > >(lowest-res, lowest-quality) JPEG from each camera I'll let you > >know what value is stored there.
Warning - technospeak ahead. Of no interest except to geeks. A pentax raw (.PEF) file conforms to the TIFF-EP standards. Like any TIFF-compliant file, it consists of a number of IFDs, each of which contains multiple tags. One of those IFDs (pointed to by the EXIF tag in the primary IFD) is the EXIF IFD. One of the tags in this IFD is a MakerNote tag. The contests of this tag are not defined by the EXIF standards; it is left as a place for the camera manufacturer to store their own manufacturer-specific data. Pentax (like several other manufacturers) choose to encode their private data in a very similar way to the TIFF-EP standards. The first four bytes of the MakerNote data are "AOC" (and a zero), for "Asahi Optical Company". This is followed by an IFD structure, although the tag values are in a Pentax-private name space. Tag 41 in that namespace introduces a single 4-byte value, which appears to be the cumulative count of shutter release cycles.
