Is Ultimate Sharpness Apochromatic?
Chromatic aberration is something photographers must live with,
the idea of color fringing due to the fact that different colors focus at
different distances from a lens. If two wavelengths of light (usually
red and blue) are brought to focus in the same plane, the lens is
called achromatic. If three or more wavelengths of light are brought
to focus in the same plane (at the same distance), the lens is
termed apochromatic, as in APO lenses. The idea is we would like
to have all the colors focus on the same plane, like on our sensor.
“APO” is a term rather loosely used by lens manufacturers. Not all
lenses labeled “APO” are really properly corrected, so just having
the term “APO” on a lens does not guarantee any particular degree
of correction. However, there are certain lenses that photographers
seem to agree do deserve to be called apochromatic, macros such
as the Coastal Optics 60mm f/4 APO, the Leica 100mm Elmarit-R
f/2.8 APO, and the Cosina/Voigtlander 125mm f/2.5 APO-Lanthar.
And there are others.
I don’t have the technical expertise of some of our members here,
but I do have a pretty good eye for images. In recent years I have
been searching for the Holy Grail of Sharpness in lenses, a true
Odyssey, for sure, and probably a bit of a fool’s errand, as some
have pointed out.
In brief, my journey lead me through the best of Nikon’s macro
lenses, on into lenses like the Voigtlander 125mm (and the others
pointed out above), and finally into the extremely sharp industrial
Nikons, such as Macro Nikon Multiphots, the Nikkor CRT, the
Repro macro, the Printing Nikkors, and others.
Although the industrial Nikkors were indeed very, very sharp, their
resulting photos still left something to be desired. It would seem
that sharpness alone is not enough, and that part of what I was
calling sharpness really turned on how color was handled. In other
words, color treatment very much affects what I was calling
‘sharpness,” which brings me to the apochromatic lenses.
When all was said and done, I seem to end up using the three APO
lenses mentioned above, the Voigtlander, the Leica, and the
Coastal Optics. I have many other fine lenses, such as the Zeiss 20