Digital BW, The Print

At 12:50 PM -0400 7/1/05, claudej1@... wrote:

>%< ...snip... >%
>
>Starting with the 200 series Kodaks, we were forced to shoot RAW (it 
>wasn't called that back then, Kodak stupidly called it a .TIF). This 
>moronic naming convention was copied by Canon (a Kodak partner for 
>the 500 series of cameras) up until very recently.
>
>%< ...snip... >%


I feel that I have to correct this totally erroneous assertion, lest 
someone get the wrong idea.

.TIF is __NOT__ the same as RAW.

.TIF (or .TIFF, etc.) is a standardized _lossless_ format for storing 
images. That is, it is an encoding which stores values that are 
derived by the recording instrument's hardware _and_software_ for 
each pixel. The data is _not_ compressed.(*)

.JPG (or .JPEG, etc.) is a standardized _lossy_ format for storing 
images. That is, it is an encoding which evaluates values that are 
derived by the recording instrument's hardware _and_software_ for 
each pixel. It performs a compression on them which analyzes adjacent 
(and other) pixels, discards certain differences, and then encodes 
the image. Depending on the image, and the level of compression, a 
lot of information can be discarded.

.RAW is an encoding of the _actual_, and unmodified, response of each 
individual pixel on the sensor. Its encoding format varies between 
manufacturers.

The difference between .TIF and .RAW is that a .TIF image has been 
manipulated by the software in the recording device and has thus lost 
any retrievable connection to the original sensor data; .RAW has not.

.RAW data is the data exactly as it was as recorded by the sensor. It 
has not been modified by the software in the recording device. This 
allows you to interpret the data (in Photoshop, etc.) without 
correcting for the mistakes and biases of the recording device's 
software (as if such correction were even possible...).

The advantages of .RAW over .TIF are essentially the same as the 
advantages of having multiple, original, unprocessed, negatives over 
having just a single processed negative.

With .RAW you can do any "development" of the "negative" anytime you 
want; including the option of combining multiple "developments" and 
layering them to improve shadow and highlight detail, or etc., etc.

With .TIFF you are committed to whatever "development" your camera 
thought was appropriate.

Moral:

.TIF is usually a bad idea, because the camera's software often makes 
bad decisions.

.JPG is almost always a worse idea, because it takes bad decisions 
and throws away a lot of data. It also takes good decisions and 
throws away a lot of data. It's an equal-opportunity 
information-rapist.

.RAW lets you look at the original data and make your own decisions. 
This is more work, but usually your decisions will be better than the 
camera's.


-=-Dennis


*  There are compressed .TIF "variations." All compressed .TIFs are lossless.



























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