[ptx] 16bit vs. HDR (was:Adobe DNG format SDK)

[Hal V. Engel]

On Tuesday 02 May 2006 01:37, Bruno Postle wrote:
> On Tue 25-Apr-2006 at 13:29 -0700, Hal V. Engel wrote:
snip 

> > But I do use UFRaw (so my images are gamma corrected) and I also color
> > manage my images during raw conversion.
>
> I'd be interested in an overview on how you do this.

This link http://lprof.sourceforge.net/help/ufraw.html will take you to a 
tutorial on how to use LProf to create profiles to color manage with UFRAW.  
This was written using screen shots from UFRAW 0.5 and LProf 1.11.2 but the 
changes to both since that time have not changed any significant details in 
the tutorial.   The UI and in particular the setting for gamma in UFRAW 0.4 
were significantly different.  So please use a newer version of UFRAW.  

Much of this can be applied to other profilers and/or other RAW conversion 
utilities.   But you may have to read between the lines to generalize this to 
other tools.   Also many RAW conversion utilities do not have color 
management built in like UFRAW and may require manual steps to be able to use 
a color profile.

The hard part is getting a good profile and 90% of getting a good profile is 
getting a good capture of the IT8 target (this applies to any profiler not 
just LProf).  I can't say this strongly enough.  90% of the times when I help 
a user that is having trouble getting a good profile it can be traced back to 
a problem with the capture or RAW processing of the IT8 image.

LProf 1.11.3 and later use a totally new regression algorithm in the profiling 
engine that is a huge improvement over earlier versions particularly in the 
darker parts of the tone curves.  So please use at least 1.11.3.  1.11.4 
should be out soon with a number of improvements including some modest 
improvements in the profiling engine as well as a translatable UI (with some 
translations).  We will also be releasing the first Windows binary since 
version 1.09.

When using color management you must use a very presice work flow when 
processing your images.   I won't go into details here other than to say that 
you must allways process your images in exactly the same way each time.

By the way the UFRAW tutorial is part of the help files that ship with LProf.

I have not tried to apply this to HDR type images or with any of the 
tools/work flows that use multi-exposure composite images.  But I think I 
will experiment with this a little.  I also don't know if any of these tools 
are color management aware.  But it seems to me that having a profile for the 
device that contains response curves based on a calibrated image like an IT8 
target would be a significant advantage. 

Hal