2005.12.22 19:09 "[Tiff] Custom Tags, Private Ifds and other questions", by David Scriven

2005.12.22 19:39 "Re: [Tiff] Custom Tags, Private Ifds and other questions", by Joris Van Damme

I sense that there are some who dislike the whole idea of a private Ifd.

In they do, they essentially dislike TIFF.

  1. Should one use a private Ifd?

I would do so. But that's merely my opinion.

It may be that you're not even allowed to allocate 13 tags. In that case, a private IFD is your only option.

  1. Since these files will definitely be out in the wild, what should be registered, and with whom?

If you go with the private IFD scheme, you need allocate only 1 tag. The tags you use inside the private IFD, are in your own private namespace, and there is no need to allocate these. If you go with the 13 private tags, you need to allocate all 13.

For actual allocation, see


If you allocate 1 or 13 private tags, and you feel the stored data may be of use to more people then yourself, please consider also submitting information in the tag directory. See near bottom of


One more thing, if you go with the private IFD, in theory you have a choice between the Long datatype and the IFD datatype. Please choose the IFD datatype, that is much more friendly on other TIFF editing code.

Joris Van Damme
Download your free TIFF tag viewer for windows here: