2018.05.11 16:15 "Re: [Tiff] Question about transfer function", by Kemp Watson

Larry:

The reason for the lamenting is that TIFF has a mechanism for dealing with custom tags, and with backwards compatibility for legacy files. But, it's been taken down by Adobe.

You can easily make a new tag - but how do you know it's not already in use, and how will others find what it is/does?

The possibility of blind proliferation of tags is the primary source of my comment about TIFF becoming less of a defined file format and more of just a container specification - interoperability will be increasingly at risk by tag collisions.

W. Kemp Watson
Objective Pathology Services Limited
Halton Data Center
8250 Lawson Road
Milton, Ontario
Canada L9T 5C6

http://www.objectivepathology.com

kemp@objectivepathology.com
tel. +1 (416) 970-7284

> On May 11, 2018, at 11:51 AM, Larry Gritz <lg@larrygritz.com> wrote:

>

>> On May 11, 2018, at 5:24 AM, Graeme Gill <graeme2@argyllcms.com> wrote:

Of course they should. Remind me again which TIFF tag is for ACES? :-)

Yes. If it doesn't exist, perhaps one could be proposed?

Notwithstanding the fact that half the traffic on this mail list is dedicated to lamenting how there is no officially recognized way to register new tags (and even if there was, we would be dealing with legacy files lacking the information for many years)...

My much more modest wish would simply be to have a string ColorSpace tag, that names an externally-referenced color configuration. While I understand the desire to support a fully embedded arbitrary transfer function, for most uses in a closed pipeline it seems wasteful to be required to fully embed what may be many MB of LUTs in every image file separately, especially when most files are either a canonical choice like "ACEScg_linear" or "sRGB", or a name in the facility's OCIO configuration.

Oh, and my second most-wished item for TIFF files would be a tag that let you name the channels of an image. (Aside: is it reasonable to use the InkNames tag for this? Even in a non-SEPARATED image?)