Because a thread about my design has been invoked, I feel I must come in and correct Mark on some of his claims made here.
... recent Grid Distortion talk in the C5E thread.
More than "talk". Actual numbers.
Furthermore, the discussion on the C5E thread was about eliminating distortion on a flat
screen. Mark often omits to mention in such discussions that he uses a tailored, curved
screen, which of course goes a long way to eliminating GD. It will with any
lens, at any throw ratio.
The MK4 uses multi-aspheric grinding in its lenses and is therefore corrected for GD (at most throws).
There is no "therefore" about it. This is just voodoo optics.
Cylindrical lenses are not classed as true aspherics.
While cylindrical lenses are, at a pedantic, technical
level, non-spherical in rotational profile, they are a trivial case of non-sphericality and are not commonly referred to in the industry as "aspherics". To do so would be to ascribe far too much sophistication to cylindrical lenses, which are a commonplace lens form.
An "aspheric" surface curvature is generally taken to mean either
non-spherical or, in the special case of cylindrical lenses, non-circular
in profile, e.g. parabolic, hyperbolic or a multi-term cubic function, to nominate three possibilities.
The cylindrical equivalent of an "aspheric" surface (i.e. one which has a non-circular, instead of a non-spherical profile) is probably better termed "atoric". If Mark is claiming his lenses are truly atoric, this would be a first, for him and for the industry.
Hence, an anamorphic adpater that uses cylindrical lenses is not truly "multi aspheric" (or if it is, then so is every other anamorphic adapter on the planet, bar none). Put bluntly, Mark's adapter
does not "correct" for distortion. He uses a curved screen
to do it, which is a whole lot simpler than all the "multi-aspheric" waffle.
If he has given up using his curved screen, and has "corrected for" GD even on flat screens, let him be the first to officially advise us all of this fact in plain English.