TIFF Specifications
===================

== EXIF IFD (and other private IFDs) ==

Because Adobe registers the private TIFF-tags, we know little about these tags in the wild. In the specification it would be suggested to use a special IFD if you need more than small amount of private TIFF tags.

This affects also the tags used for EXIF data. Our interpretation is, if you have an IFD for private tags, they should only be referenced from this IFD and not from base IFD directly.

== offsets on word boundary ==

The specification is very clear. Offsets should only point to odd addresses. We think this is important for longterm preservation, because it makes the TIFF format more robust and repairable if some bit flipping occurs.

== tags in ascending order ==

see offset and word boundary, same reason

== ASCII ==

The specification defines ASCII as chars with bytes 0-127 (see section "Types",
page 16 of TIFF 6.0 spec). But some tags with type ASCII have additional
constraints. For full ASCII-range you could use the value "fullascii" in the
config file. If you want to ensure only printable ASCII is used, try
"printascii". You could also use the regex-value, which understands the POSIX
character classes. Therefore you could use "^[[:print:]]\+$" as replacement.
