Here's the relevant portions of the notes:

>   The way POV-Ray 3.7 handles the 'assumed_gamma' keyword has changed.
>   Previously the presence of this keyword in global_settings caused a
>   'possible error' warning and its presence was ignored. In addition
>   no gamma correction was available in previous betas. Starting with
>   beta.10 however, gamma correction is performed on both the display and
>   file output, subject to the following criteria:
> 
>     o If the scene language version is set to 3.7 (or not set at all), then
>       gamma correction will default to ON, with the value used being set by
>       the 'display_gamma' INI file setting. Note that in previous versions of
>       POV-Ray gamma correction was OFF by default but otherwise this is the
>       same.
> 
>     o If the scene language version is set to earlier than 3.7, then gamma
>       will be OFF by default.
> 
>     o Notwithstanding the above, if the keyword 'assumed_gamma' is present
>       in the scene's global_settings, then POV will take one of the following
>       actions:
> 
>         a) if "assumed_gamma 2.2" is present, gamma correction will be turned
>            OFF and a warning issued. the same thing will happen if the value
>            specified is not 2.2 but happens to be the default for the platform
>            setting given to POV-Ray when it was compiled (e.g. Windows is 2.2).
> 
>         b) if "assumed_gamma 1.0" is present, gamma correction will be turned
>            ON (if it's not already on) and in any case a warning will be issued.
> 
>         c) if a value other than the above is specified, it is ignored and a
>            'possible error' message is issued.
> 
>       You will note from the above that therefore it is no longer possible to
>       adjust the amount of gamma correction from a scene file. This is as
>       designed since scene files should be as much as possible be platform
>       independent, and the gamma of particular display hardware does not belong
>       in the scene file. If you really need to specify 'assumed_gamma' you can
>       do so in an INI file or on the command-line; however in those cases you
>       may as well just use 'display_gamma' in its place.
> 
>       When writing file formats that support gamma specification, the inverse
>       of the assumed_gamma value will be embedded in the file headers, so that
>       an appropriately equipped display program can 'undo' the gamma correction
>       if it is so desired. This is as per previous versions of POV-Ray.
> 
>   Frontend and Backend
>   --------------------
>       
>   Note that POV-Ray uses a logical separation of frontend and backend. The
>   'frontend' is that part which deals with the user-interface, locating files,
>   parsing command-line options, reading INI files, and so forth. The 'backend'
>   deals with parsing the scene file and doing the actual render. These two parts
>   of POV-Ray communicate via a message-passing interface, even when linked into
>   the one executable program.
>   
>   Whilst currently not supported, it is entirely possible to separate the front
>   and back ends via for example a network interface, and have the render done
>   on one machine while the user interface (and display) is on another. Knowing
>   this may make it easier to understand why, for example, we are moving away
>   from allowing things such as gamma correction to be specified in the scene
>   file; there is no reason to assume the scene file is on the same machine as
>   the image will be displayed upon, and as such the specification of gamma
>   should be done in the frontend via INI or command-line options.
> 
>   There will be more changes along these lines as we prepare for the future
>   transition to a fully network-capable renderer. The POV-Team will attempt
>   to ease the change to the new system by doing things such as the assumed_gamma
>   interpretation above, where it is possible to do so.

-----------

>   gamma changes, revert to beta.10 behaviour with some tweaks for more 
>   extensive version checking.
>   
>   In particular, specifying -MV3.7 or later via an INI file or the 
>   command-line is taken at higher precedence than a #version 3.6 (or 
>   lower) in the scene file when it comes to assigning the default state of 
>   gamma correction (on/off, not its actual value if on). the value used 
>   when it is on is determined by either Display_Gamma (if given) or 
>   DEFAULT_DISPLAY_GAMMA otherwise. Similar steps are taken for the new 
>   File_Gamma option.
>   
>   The actual value of assumed_gamma is not passed on; this prevents its 
>   use for anything other than turning gamma on or off (which is what the 
>   majority of scenes did with it). Those scenes that (mis)used 
>   assumed_gamma to adjust the scene appearance outside of the needs of the 
>   user's actual display gamma will need to either be altered to suit, or 
>   to be run with an adjusted Display_Gamma and File_Gamma.
>   
>   NB users are warned that assumed_gamma support will be removed entirely 
>   in a later 3.7 revision.

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