--- a/src/sage/interfaces/tachyon.py
+++ b/src/sage/interfaces/tachyon.py
@@ -140,14 +140,14 @@ written in the sequence they are listed in the examples in this section.
 The ``PROJECTION`` keyword must be followed by one of the supported
 camera projection mode identifiers ``PERSPECTIVE``, ``PERSPECTIVE_DOF``,
 ``ORTHOGRAPHIC``, or ``FISHEYE``. The ``FISHEYE`` projection mode
-requires two extra parameters ``FOCALLENGTH`` and ``APERTURE`` which
+requires two extra parameters ``FOCALDIST`` and ``APERTURE`` which
 precede the regular camera options.
 
 ::
 
    Camera
      projection perspective_dof
-     focallength 0.75
+     FOCALDIST 0.75
      aperture 0.02
      Zoom 0.666667
      Aspectratio 1.000000
--- a/src/sage/plot/plot3d/tachyon.py
+++ b/src/sage/plot/plot3d/tachyon.py
@@ -92,7 +92,7 @@ angle, right angle)::
 Finally there is the ``projection='perspective_dof'`` option. ::
 
     sage: T = Tachyon(xres=800, antialiasing=4, raydepth=10,
-    ....: projection='perspective_dof', focallength='1.0', aperture='.0025')
+    ....: projection='perspective_dof', FOCALDIST='1.0', aperture='.0025')
     sage: T.light((0,5,7), 1.0, (1,1,1))
     sage: T.texture('t1', opacity=1, specular=.3)
     sage: T.texture('t2', opacity=1, specular=.3, color=(0,0,1))
@@ -186,7 +186,7 @@ class Tachyon(WithEqualityById, SageObject):
       or ``'fisheye'``.
     - ``frustum`` - (default ''), otherwise list of four numbers. Only
       used with projection='fisheye'.
-    - ``focallength`` - (default ''), otherwise a number. Only used
+    - ``FOCALDIST`` - (default ''), otherwise a number. Only used
       with projection='perspective_dof'.
     - ``aperture`` - (default ''), otherwise a number.  Only used
       with projection='perspective_dof'.
@@ -331,7 +331,7 @@ class Tachyon(WithEqualityById, SageObject):
     Use of the ``projection='perspective_dof'`` option.  This may not be
     implemented correctly. ::
 
-        sage: T = Tachyon(xres=800,antialiasing=4, raydepth=10, projection='perspective_dof', focallength='1.0', aperture='.0025')
+        sage: T = Tachyon(xres=800,antialiasing=4, raydepth=10, projection='perspective_dof', FOCALDIST='1.0', aperture='.0025')
         sage: T.light((0,5,7), 1.0, (1,1,1))
         sage: T.texture('t1', opacity=1, specular=.3)
         sage: T.texture('t2', opacity=1, specular=.3, color=(0,0,1))
@@ -365,7 +365,7 @@ class Tachyon(WithEqualityById, SageObject):
                  look_at=[0, 0, 0],
                  viewdir=None,
                  projection='PERSPECTIVE',
-                 focallength='',
+                 FOCALDIST='',
                  aperture='',
                  frustum=''):
         r"""
@@ -391,7 +391,7 @@ class Tachyon(WithEqualityById, SageObject):
             self._camera_position = (-3, 0, 0) # default value
         self._updir = updir
         self._projection = projection
-        self._focallength = focallength
+        self._FOCALDIST = FOCALDIST
         self._aperture = aperture
         self._frustum = frustum
         self._objects = []
@@ -624,9 +624,9 @@ class Tachyon(WithEqualityById, SageObject):
         camera_out = r"""
            camera
               projection %s""" % (tostr(self._projection))
-        if self._focallength != '':
+        if self._FOCALDIST != '':
             camera_out = camera_out + r"""
-              focallength %s""" % (float(self._focallength))
+              FOCALDIST %s""" % (float(self._FOCALDIST))
         if self._aperture != '':
             camera_out = camera_out + r"""
               aperture %s""" % (float(self._aperture))