MAKER_NOTES

# @(#) $Id: MAKER_NOTES,v 1.8 2005/07/05 17:02:24 alex Exp $

Only  one camera  maker  (Foveon, for  the  Sigma/Foveon camera)  currently
publishes the form  or interpretation of their makernote data;  the data is
apparently recorded just to make the image file larger.

Exifprobe's  identification and  interpretation  of tags  in MakerNotes  is
based largely upon  information reverse-engineered by others  and posted to
the Web  (see CREDITS). A  few items are  based upon examination  of images
downloaded from  websites whose  operators are kind  enough to  make camera
images available for download (including some rather *large* images).

I recommend that you examine any  output for your camera to assure yourself
that the  associations between  tag identifiers  and the  interpretation of
the  associated values  is  reasonable  and correct.  Please  report to  me
(dhh@virtual-cafe.com) any  corrections you  think should  be made  for any
make or model of camera, and  any additional information you may deduce for
any camera (or other device).

It should be  noted that tag numbers, types, and  values shown by exifprobe
will be correct  if shown...they are read directly from  the image file. It
is  the "interpretation"  of  tags  and associated  values  which could  be
suspect.

The strategy used by exifprobe to  read MakerNotes does *not* depend upon a
table of makes and models. The program  scans the offset given for the note
to see if it can find an ID string, a TIFF header, and/or a valid IFD entry
or two  at a  reasonable offset  and in either  byteorder. The  features it
finds are recorded as a "scheme" which is used for reading and printing the
MakerNote information.  If a valid IFD  is found the program  consults make
and model information for the oddball variations used by some manufacturers
(e.g. offsets relative to the start of the note or start of each entry) and
to see if tagnames and value interpretations are available. If tagnames and
interpretations are not available, the program will print the raw data with
tagnames constructed from the tag number.


dhh@virtual-cafe.com