TIFF RAW JPEG etc

cmr164

There is lots of confusion about TIFF and about RAW so I'll start with JPEG.

JPEG == (Joint Photographic Experts Group) A lossy compressed format supporting 1-24bit depth images. Because of the extreme compression possible, one can have large true colour images that still have a reasonbly small file size and that makes jpegs the web's favourite format. Repeated edits and saves will severely degrade the image because of the loss of information in each cycle.

RAW == A variety of file formats whose common characteristic is that the data of each of the imager sensors is saved. In a classic Bayer Mask sensor the data will be GRGB with 8-16 bits each. On DSLRs the norm is 12bits per sensor. This data may be stored in a proprietary format like Canon's or embedded in TIFFs like the Kodak pro cameras do.

and that brings me to TIFF a subject where what is commonly known is just plain wrong.

TIFF == (Tagged Image File Format) Contains encapsulated image data that can be compressed RAW like the Kodak tiffs or encapsulated uncompressed RGB 8 or 16 bit data (which is what common knowledge thinks of as a tiff) or it can encapsulate any format that is registered. There is even a tiff whose embedded image is a jpeg. The reality is that tiff describes the file format but does not describe the image format.

wxwax

Cool. I didn't know that. Thanks for the explanation. I understand some, but not all of your vocabulary. It might help us understand precisely what you're telling us if you define these words and terms (in English!)


Lossy
True color
Compression
File format
Bits
GRGB
RGB

cmr164

wxwax wrote:

Cool. I didn't know that. Thanks for the explanation. I understand some, but not all of your vocabulary. It might help us understand precisely what you're telling us if you define these words and terms (in English!)


Lossy
True color
Compression
File format
Bits
GRGB
RGB

I will assume the above is at least in part a joke... but will answer anyway

From Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.
lossless \Loss"less\, a. Free from loss. [Obs.] --Milton.
(me: Lossy is the opposite of 'lossless' )

From WordNet ® 1.6, © 1997 Princeton University
Compression ... 3: encoding information while reducing the bandwidth or bits required

RGB - Red Green Blue (usual computer image represntation)

GRGB - Green Red Green Blue (usual imager sensor config)

Bits - individual binary storage elements

True Color - actually a misnomer. used to describe 24bit (and greater) colour representation in the theory that the difinition of more colours than the eye can differentiate can be considered true color.

File format - the structure of information within a computer storage system's discreet files.

See the following for additional info:

Phil Askey's site (even if he doesn't understand TIFF):
http://www.dpreview.com/learn/Glossary/Digital_Imaging/

and Martin Brown's site:
http://www.nezumi.demon.co.uk/photo/bayer/bayer.htm

wxwax

Excellent, thanks. I knew some of them, but didn't know the definitions of true color, bit... and I thought the extra G in front of GRGB might have been a typo. Also this helps others who know even less than I do (I'm sure they exist, somewhere on this planet.)