TIFF

The Tagged Image File Format is a widely used and open Image format used to store and exchange digital images of all kinds. General information on TIFF on Wikipedia: [1]

TIFF is a very versatile file format with many flavors.

Compression issues

TIFF can contain almost any image data. However, there are some common forms of image data compression found inside a TIFF file:

• No compression is the most compatible form but results in the largest files.
• JPEG Simply a JPEG file stored inside a TIFF tag, lossy compression.
• LZW is a very common, lossles compression scheme resulting in smaller files. LZW was patented in most countries until 2004 and hence was not found in many freeware distributions.
• ZIP is lossles too but not very common although it usually results in smaller files than LZW and was not patented.
• PackBits A not very common, lossless compression scarcely supported by image editing software. Photoshop for example can read PackBits compressed TIFFs but not write them.
• G3 and G4 compression is used for FAX documents only.

PTStitcher (and hence all GUIs like hugin, PTAssembler, PTGui or PTMac) outputs PackBits compressed image files if the output format is TIFF. There is a bug in Photoshop prior to Version 9 (CS2) that prevents to open PackBits compressed files beyond a ertain size. See Opening large TIFFs with Photoshop for details.