Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Austin 
Franklin" <darkroom@i...> wrote:

> I disagree that it's "more correct".  "Transfer function" 
>is far less precise term than LUT


Being less precise is EXACTLY why it's more correct.

As I said in my prior post, I wanted a generic term.  "Generic" 
and "precise" are opposites.

The problem with LUT is that it's specific to a particular 
implementation, and furthermore we don't even know which, if **ANY** 
Photoshop or driver features are implemented with LUTs (although I 
suspect many are).   So LUT is about as bad a term as you can get 
because there's no way to know when it's correct.

The problems with "curves" is twofold -  1,  The actual term "Curves" 
is used for some Photoshop tools, which makes it ambiguous because 
the reader doesn't know if you are speaking gererically or about a 
specific tool, and two, not all transfer functions are represented 
with curves. 

"Transfer Function" has two advantages:  
1. It's generic - it describes ANY module, tool, or stage, where one 
set of values is mapped to another, thus encouraging users to think 
outside the box.
2.  It is the technically correct term.  I work in image processing 
and my colleagues and I were discussing this today.  The consensus 
was that if we don't say "transfer funtion" then the only other 
correct term would be "mapping function".


> What you were describing is merely addition, typically
> implemented as a LUT.

A LUT doesn't do addition; it takes an index and outputs a value.  

> Yes, more happens after the tonal curve adjustment before 
> ink gets to the paper, but we weren't talking about that.

I was.  That's why I brought it up.  It's important for us to 
understand, and be able to manipulate as much as possible every step 
in the processing pipeline from the RGB values in our original image 
before Photoshop ever touches it, to when the printer sprays dots of 
ink on the paper.