2004.10.05 08:43 "Re: [Tiff] Re: BigTIFF extension issue", by Andy Cave

Hi Chris.

Photoshop PSD -> 8 byte offsets became PSB because users couldn't understand why it wouldn't open in older versions of Photoshop (having been mostly compatible from 3.0 to 7.0).

A good example. Albeit of an internal single company format as opposed to an external public format. So slightly different.

PDF and EPS are examples where the version number didn't change, but older apps may break or not read the files.

That's not an example of where the extension changed. Although it is a good example of where older apps would break (for various reasons - PS1 went though various revisions without any version changes - color extensions,... and then PS2 added new operators,... and...).

JPEG -> JPEG2000: same group, same goal, different format, different extension

This is a good example of where a new file format (jp2) was designed and the contents (encoded stream) changed, so it did need a new extension. Not the same thing we're discussing.

Most of my other examples are along the lines of PSD -> PSB, but aren't image formats.

So, we only have one 'similar' example with Photoshop.

Did no-one have any comments re my mail about defining the bigtiff spec in a backwards compatible way? If we did this, then the question on extension becomes mute.

_andy.

PS Perhaps its about time we added a version number tag to TIFF if there's not one already.