2003.02.28 20:58 "Re: Photoshop tiff limits", by Chris Cox

I have a question which I hope someone can shed some light on. I work with very large image files in the mapping industry. It is not uncommon for me to generate tiff images in the range of 2 Gigs filesize. We have found that Photoshop will only open a tiff that is at or under a resolution of 30000 x 30000 pixels.

That is correct.

And in the context of 24 bit imagery, there seems to be a limit of about 2GB on the filesize for opening successfully.

That is also correct.

Why is that exactly?

Because the older APIs for file I/O used signed 32 bit quantities, imposing a 2 GB limit on filesizes.

The newer APIs require quite a bit of application code to change, and haven't been too stable until recent OS versions.

The 30,000 pixel limit is because Photoshop was originally written to use 16 bit signed values for pixel coordinates.

Chris