DOCS/options: make --scale documentation more consistent

Beef up the barebones description for the Mitchell filter and make it
consistent with the other --scale examples. In addition to this, make
some wording changes to make the language in the documentation a bit
more unified.

Before this change it was pretty obvious that multiple authors
contributed to this part of the manual (at completely different
timeframes), so the language was somewhat disjointed. The Mitchell
description was also not very helpful.

DOCS/man/options.rst

@@ -5299,8 +5299,8 @@ them.
         (This filter is an alias for ``jinc``-windowed ``jinc``)
 
     ``ewa_lanczossharp``
-        A slightly sharpened version of ewa_lanczos. This is the default when
-        using the ``high-quality`` profile.
+        A slightly sharpened version of ``ewa_lanczos``. This is the default
+        when using the ``high-quality`` profile.
 
     ``ewa_lanczos4sharpest``
         Very sharp scaler, but also slightly slower than ``ewa_lanczossharp``.
@@ -5309,8 +5309,10 @@ them.
         built-in anti-ringing, so no extra action needs to be taken.
 
     ``mitchell``
-        Mitchell-Netravali. The ``B`` and ``C`` parameters can be set with
-        ``--scale-param1`` and ``--scale-param2``.
+        Mitchell-Netravali. Piecewise cubic filter with a support of radius 2.0.
+        Provides a balanced compromise of all scaling artifacts. This filter has
+        both ``B`` and ``C`` set to ``1/3``. The ``B`` and ``C`` parameters can
+        be controlled with ``--scale-param1`` and ``--scale-param2``.
 
     ``hermite``
         Hermite spline. Similar to ``bicubic`` but with ``B`` set to ``0.0``.
@@ -5319,10 +5321,9 @@ them.
         default for ``--dscale``.
 
     ``catmull_rom``
-        Catmull-Rom. A Cubic filter in the same vein as ``mitchell``, where
-        the ``B`` and ``C`` parameters are ``0.0`` and ``0.5`` respectively.
-        This filter is sharper than ``mitchell``, but it results in more
-        ringing.
+        Catmull-Rom spline. Similar to ``mitchell``, but with ``B`` and ``C``
+        set to ``0.0`` and ``0.5`` respectively. This filter is sharper than
+        ``mitchell``, but prone to ringing.
 
     ``oversample``
         A version of nearest neighbour that (naively) oversamples pixels, so