[MF3D.FORUM:982] New Ekeren MF viewers

[Paul Talbot <ptww@xxxxxxxxx>]

As mentioned in the previous message, new MF stereo
viewers from Jacob van Ekeren were demonstrated at
the NSA 2000 convention in Mesa.  Below is my review
of the viewers that were demonstrated.

As is typical of Ekeren viewers, design and craftsmanship
combine to present a very attractive, "industrial" package.
Being primarily plastic, they did not strongly appeal to
my sense of aesthetics, but others were drawn to the solid,
manufactured look.  The viewers are also very compact, for
three reasons: 1) they leave the extra 10mm height of KI/RMM
mounts (compared to European MF mounts or Gepe mounts)
sticking out above the viewer; 2) they use fairly short FL
lenses, and only the lenses, not an entire front viewer
panel, move as focus is adjusted; 3) the detachable lightbox
is extremely compact.

The viewers created quite a buzz; I felt almost inundated
with glowing reviews of them before I'd even checked into
my room at the hotel, and that was early Wednesday morning!
The WOW factor of a first look in the viewer is very high.
That may be due in part to the large apparent image size
and excellent crispness--at least at first glance.

The lenses are the Horizon medium format 4X loupes that
have been discussed on this list.  As it turns out, the
Horizon loupes, IMO, are a definite weak point of the viewer.
The initial impression of excellent crispness, sadly, only
holds for a small sweet spot in the center of the lens, and
only while viewing the center of the image.  The corners
are definitely fuzzy, enough so to be disturbing to at
least some users.  I found it very bothersome; some people
only noticed after it was pointed out to them; and one
person I handed the viewer to put it down within a few
seconds saying "there's something wrong with the lenses."

Ekeren uses the built-in focus mechanism of the loupes to
provide separate focusing of the two lenses.  That means
that the lenses can be set to offset differential focus
of the user's two eyes.  It also cleverly allows for the
success of the overlapping Gepe mount viewer design,
where the right image is closer to the eyepiece than is
the left image.  (See next message for more on overlapping
Gepe mounts.)  Personally, I might like separate lens
focusing as a supplement to the primary focus mechanism,
but I don't really care for having separate lens focusing
as the only way to focus a viewer.

I've been told the FL of the Horizon MF loupe is around
62mm; that's quite a bit shorter than what Greg Erker
measured for his Horizon 4X non-MF loupes.  While it was
not something I noticed in normal use, careful comparison
between the Horizon loupes and the Edmund's 46x78 achromats
seemed to show a definite "squash" effect with the loupes.
I measured the viewing distance and found that with the
loupe set to closest focus, the distance from the slide to
the eye side of the lens is about 67mm; at farthest focus
it is about 77mm.  For comparison, minimum viewing distance
with the SaturnSlide(tm) viewer is about 77mm, and maximum
is about 99mm.  I would like to give a comparison of the
"in focus" viewing distances, but for some reason I can
barely discern any difference between even the two extremes
of travel of the Horizon loupes at the distance they are
mounted from the slide slot.  The numbers above probably
understate the difference in the FL of the lenses: at the
minimum distances, the SaturnSlide(tm) is almost in focus
for my uncorrected near-sighted eyes.  At minimum distance,
the Ekeren viewer is nowhere near in focus for my uncorrected
vision.

The short FL has at least two other effects: it makes
the image seem larger, making the view somewhat more
immersive.  At the same time, it makes it very difficult
for the smallish diameter of the lenses to fully cover
MF images.  Users without eyeglasses reported being able
to see all of both images simultaneously.  Wearing glasses
in front of my narrowly spaced eyes, I could see all of
one image but lost a significant chunk of the other image
to insufficient coverage.  The demo versions of the viewer
do not have inter ocular adjustment, although the smallish
size of the lenses would indicate it could be useful.

One impressive aspect of the Horizon loupes was the extremely
flat view.  Pincushion/barrel distortion was virtually non-
existent.  The loupes are described as "achromatic," but
unfortunately there was definite chromatic aberration visible
in the white edges of an RMM mount.  I was shocked to see
chromatic aberration; it's not a defect I've ever had much
sensitivity to, even with the cheap plastic lenses in the
infamous $3 viewer.

To conclude my comments on the optical portion of the
Ekeren MF viewers, I'd say the viewer seems very well
suited to 645 shooters using camera lenses in the 60mm
range.  I think a good number of 6x6 shooters would also
enjoy the viewers, especially those that prefer a modern
manufactured look rather than a traditional hand-crafted
look.  I don't think, however, that charter members of
this list (e.g., Joel A., John B., Greg E.) would find
the viewers acceptable, due to the non-ortho and relatively
poor optical performance of the lenses, compared to the
lenses Alan Lewis has selected for the various editions
of his viewer and kit, or that several others here have
used in their own viewers.

Jacob is known for putting a lot of engineering into his
lightboxes, and the detachable lightbox was definitely the
most impressive part of his MF viewers.  I could not get
over the fact that he manages to fully illuminate an MF
stereo slide with a single halogen bulb!  Lighting was
bright and perfectly smooth side to side and bottom to
top.  The compact attachment snaps on to the main viewer
via a clip on the right and left sides.

Pricing of the Ekeren MF viewers is not yet known.  The
demo unit of the twin Gepe version reportedly had would-be
purchasers standing in line, and ended up selling at quite
a premium to expected retail.  (It didn't quite hit 4 figures,
but according to rumors on the floor of the trade show it
was within hailing distance of that mark.)

Paul Talbot

SaturnSlide is a trademark of Alan Lewis