I just got my two new viewers in the mail today.

I rushed to put batteries to try one viewer. I looked at several slides
and then took the viewer apart. Here are my impressions:

- Optical: The lenses has wonderful coated 32mm dia. achromatic lenses.
This was a huge relief for me.

The lenses are held with a metal ring (one of the few metal pieces in the
viewer). You can easily unscrew this ring and remove the lenses, if you
want to use the lenses for another viewer, or try different lenses in this
viewer (there is room for shorter FL lenses - read below).

In the name of science I destroyed a STL ("Steal the light") 3D World
viewer and it appears that the lenses are identical (I replaced one lens
of the focusing viewer with a lens of the STL viewer and I could not see a
difference when viewing in stereo).

- Construction: The viewer is mostly plastic. There is a focusing
adjustment (lenses move back and forth via two levers on the side. There
is a plastic gear & pinion system that moves them. The adjustment is not
tight or precise. There is a small interocular adjustment, the lenses can
slide just a bit. This is just based on friction, there are no clicking
stops or anything like that. In other words, the construction is very
simple and I am afraid there is no room for abuse or rough handling or too
much taking apart and putting back again.

- Illumination: The viewer operates on 3 x AA batteries and a push-button
switch at the top. The light is bright and mostly uniform. There was
some concern about dust accumulating at the diffuser. After a few minutes
of use some specs of dust were already gathering at the reflector.

- Taking the viewer apart: At first I could not see a way to take the
viewer apart, but then I found it is very easy. There is a little screw
inside the battery compartment. Remove the screw and you can take the
viewer apart to inspect the illumination unit and clean the diffuser (also
gain access to the parts the control the focusing and interocular).
Illumination is done with an array of 20 LEDs sitting at the bottom of the
illumination unit, which is quite thin.

Overall, it is a nice viewer, however it has (or I have) a problem with
the adjustments:

A. Focusing. The focusing range is extremely long, however, even with the
lenses pulled as far away from the slide as possible, I still cannot focus
infinity properly. I have very good distant vision. Like its STL
brother, this viewer will not focus at infinity. It requires a small
accommodation of the eyes. This is just stupid, to be bland. They put
this extremely long focusing range, only it is one-sided and the viewer is
designed for myopic users. People were happy to hear that this is a
focusing viewer, thinking that finally they can bring their MF slides in
focus... Well, they still can't, unless if they are myopic.

Considering how easy it is to change lenses, one could try to find and put
shorter FL lenses. This will give stronger magnification and better
centered focusing range.

B. Interocular adjustment. One problem that I have with the STL viewer is
that I have hard time fusing infinity in the 3D World mounts, because the
spacing of the openings in the mounts is around 65mm and the spacing of
some MF mounts is 65mm and others is 62mm. Ideally, the spacing of the
viewer lenses should be equal to the infinity spacing of the images. I
would say, for the MF mounts that have openings centered at 62mm, the
spacing of the lens viewers should be 65mm. If there is an adjustment of
the spacing of the lenses, this should go higher than this value. Well, I
measured the interocular adjustment of the lenses and it goes from 61mm to
65mm. I can only use this viewer at the widest separation of the lenses
(65mm) and I still have a problem fusing infinity. I think a better range
should have been 65-69mm.

I tried the viewer with my wife and she has no problem with the focusing
(at the extreme end) or the interocular.

I would like someone else to confirm my findings and try the viewer with
his own personal MF slides, so I am planning to send viewer #2 to John
Thurston to do a quick analysis.

It seems that with a little hacking, I could solve the adjustment issues.
For example, the metal ring that screws to hold the lenses in place, has
quite a long travel. It is possible to put a rubber ring behind the lens,
to push it a bit forward, and then still screw the ring in place. This
will take care of the focusing. I am sure one could trim some parts (they
are all plastic) and increase the interocular. But why would anyone have
to do this?

Regarding the price, this viewer costs 3x to buy wholesale and I expect
its retail price to be 2-3x the price of the STL viewer, so around
$70-$100. If the adjustments were to my linking, I would have no problem
paying this amount for a good viewer like this.

I am planning to bring the adjustment issues to 3D World's attention to
see what they say and they wait for John's evaluation before buying a
large quantity for resale.

George Themelis

DrT (George Themelis) wrote:

> designed for myopic users. People were happy to hear that this is a
> focusing viewer, thinking that finally they can bring their MF slides in
> focus... Well, they still can't, unless if they are myopic.
>

fwiw - being myopic, that sounds like good news to me. :-)

Mike K.

Hey George,

At 12:56 PM 9/3/2008, you wrote:

>I just got my two new viewers in the mail today.
>
>I rushed to put batteries to try one viewer. I looked at several slides
>and then took the viewer apart. Here are my impressions:
>
>- Optical: The lenses has wonderful coated 32mm dia. achromatic lenses.
>This was a huge relief for me.
>
>The lenses are held with a metal ring (one of the few metal pieces in the
>viewer). You can easily unscrew this ring and remove the lenses, if you
>want to use the lenses for another viewer, or try different lenses in this
>viewer (there is room for shorter FL lenses - read below).
>
>In the name of science I destroyed a STL ("Steal the light") 3D World
>viewer and it appears that the lenses are identical (I replaced one lens
>of the focusing viewer with a lens of the STL viewer and I could not see a
>difference when viewing in stereo).

Interesting. So much for my translation of that web page that led me
to believe the new viewer had a focal length of 65mm. It's got the
same 32x75mm achromatic doublets.

>- Construction: The viewer is mostly plastic. There is a focusing
>adjustment (lenses move back and forth via two levers on the side. There
>is a plastic gear & pinion system that moves them. The adjustment is not
>tight or precise.

And even though there are two focus levers, I supposed they don't
operate independently for each eye (or you would have mentioned
that). It's a good thing, too, or you'd end up with a different
angular magnification for each eye.

>There is a small interocular adjustment, the lenses can
>slide just a bit. This is just based on friction, there are no clicking
>stops or anything like that. In other words, the construction is very
>simple and I am afraid there is no room for abuse or rough handling or too
>much taking apart and putting back again.
>
>- Illumination: The viewer operates on 3 x AA batteries and a push-button
>switch at the top. The light is bright and mostly uniform. There was
>some concern about dust accumulating at the diffuser. After a few minutes
>of use some specs of dust were already gathering at the reflector.

Bummer - I first suggested dust could be a problem with this new
viewer 20 months ago - way back on December 27, 2007:

"I agree. It's premature to judge their design only by that photo,
but the light panel appears to be way too thin. Any dust on the
surface of the diffuser will likely be too close to the film plane to
be out-of-focus and the diffuser might also be too close to the light
source - providing uneven illumination. Asking them for
detailed specifications is a waste of time. We'll just have to wait
and see." Source: http://tech.groups.yahoo.com/group/MF3D-group/message/1522

If the dust is easy to remove, I won't be too disappointed, but it's
been a long wait only to find out that 3DWorld are making mistakes
that dozens of people could have warned them about if only they had
sought our experience. Now the molds are cast and we're stuck with
using a cart that has square wheels. :-(

>- Taking the viewer apart: At first I could not see a way to take the
>viewer apart, but then I found it is very easy. There is a little screw
>inside the battery compartment. Remove the screw and you can take the
>viewer apart to inspect the illumination unit and clean the diffuser (also
>gain access to the parts the control the focusing and interocular).
>Illumination is done with an array of 20 LEDs sitting at the bottom of the
>illumination unit, which is quite thin.

That's good news that you can take it apart to clean the diffuser,
but is the illumination unit so thin that the lighting is "blotchy"
instead of uniform?

>Overall, it is a nice viewer, however it has (or I have) a problem with
>the adjustments:
>
>A. Focusing. The focusing range is extremely long, however, even with the
>lenses pulled as far away from the slide as possible, I still cannot focus
>infinity properly.

I'm going to sound terribly unappreciative here, given that we are
truly fortunate to have anyone out there producing viewers for us,
but this inability to focus at Infinity, combined with the overly
thin illumination unit, and the too-closely positioned diffuser,
suggests that 3DWorld were hell-bent on making this viewer as compact
as possible, at the expense of performance. Doh!

>I have very good distant vision. Like its STL
>brother, this viewer will not focus at infinity. It requires a small
>accommodation of the eyes. This is just stupid, to be bland.

Amen!

>They put
>this extremely long focusing range, only it is one-sided and the viewer is
>designed for myopic users. People were happy to hear that this is a
>focusing viewer, thinking that finally they can bring their MF slides in
>focus... Well, they still can't, unless if they are myopic.
>
>Considering how easy it is to change lenses, one could try to find and put
>shorter FL lenses. This will give stronger magnification and better
>centered focusing range.

That's a thought - and 32mm diameter achromats are relatively
plentiful (compared to greater diameters), but we'll probably pay as
much for a pair of shorter lenses as for this poorly designed viewer.

>B. Interocular adjustment. One problem that I have with the STL viewer is
>that I have hard time fusing infinity in the 3D World mounts, because the
>spacing of the openings in the mounts is around 65mm and the spacing of
>some MF mounts is 65mm and others is 62mm. Ideally, the spacing of the
>viewer lenses should be equal to the infinity spacing of the images. I
>would say, for the MF mounts that have openings centered at 62mm, the
>spacing of the lens viewers should be 65mm. If there is an adjustment of
>the spacing of the lenses, this should go higher than this value. Well, I
>measured the interocular adjustment of the lenses and it goes from 61mm to
>65mm. I can only use this viewer at the widest separation of the lenses
>(65mm) and I still have a problem fusing infinity. I think a better range
>should have been 65-69mm.

Somebody shoot me. I have a 70mm IPD. If the viewer works at all
for me, I'll be at the extreme limits of the clear apertures - way
off-axis. Arrrgh!

>I tried the viewer with my wife and she has no problem with the focusing
>(at the extreme end) or the interocular.
>
>I would like someone else to confirm my findings and try the viewer with
>his own personal MF slides, so I am planning to send viewer #2 to John
>Thurston to do a quick analysis.
>
>It seems that with a little hacking, I could solve the adjustment issues.
>For example, the metal ring that screws to hold the lenses in place, has
>quite a long travel. It is possible to put a rubber ring behind the lens,
>to push it a bit forward, and then still screw the ring in place. This
>will take care of the focusing. I am sure one could trim some parts (they
>are all plastic) and increase the interocular. But why would anyone have
>to do this?

A hacking we shall go.... :-)

>Regarding the price, this viewer costs 3x to buy wholesale and I expect
>its retail price to be 2-3x the price of the STL viewer, so around
>$70-$100. If the adjustments were to my linking, I would have no problem
>paying this amount for a good viewer like this.

Even as it is, it's a steal at $100, but I'm guessing it wouldn't
have cost more than an additional $5.00 to produce a less compact
design addressing the flaws you've uncovered.

>I am planning to bring the adjustment issues to 3D World's attention to
>see what they say and they wait for John's evaluation before buying a
>large quantity for resale.

Here's hoping they can make changes without taking too great a loss.

Mike Davis

Thanks Mike for your comments...

One thing I like about 3d World is that they respond right away to
questions/concerns about their products, and they seem willing to correct
problems. Of course, the thing I don't like is that they design and
produce these products without first getting feedback from knowledgeable
users.

Anyway, I sent them an email summarizing my concerns regarding the
adjustments and I already received a response from the person in charge,
and they basically say that 1) The viewer should be focused at the center
of the focusing range (in other words, the focusing range is centered
around a normal person's eyes), 2) The interocular was designed to be
61-66mm.

I guess I disagree about #1 and we need to discuss if this is the range
the viewer should have (#2).

I am sending the two viewers to John and Mike for independent evaluation.

George Themelis

>>I am planning to bring the adjustment issues to 3D World's attention to
>>see what they say and they wait for John's evaluation before buying a
>>large quantity for resale.
>
> Here's hoping they can make changes without taking too great a loss.

Thank you for your most thorough description !

> - Optical: The lenses has wonderful coated 32mm dia. achromatic

lenses.

> This was a huge relief for me.

To all of us, I gather... given there was some concern they might
use cheaper lenses.

> The lenses are held with a metal ring (one of the few metal pieces

in the

> viewer). You can easily unscrew this ring and remove the lenses,

if you

> want to use the lenses for another viewer, or try different lenses

in this

> viewer (there is room for shorter FL lenses - read below).

Good to know, but then the 3D World lenses are one of the most
positive points about this viewer so replacing them might seem
conterproductive unless one finds extraordinary lenses...

> - Construction: The viewer is mostly plastic. There is a

focusing

> adjustment (lenses move back and forth via two levers on the

side. There

> is a plastic gear & pinion system that moves them. The adjustment

is not

> tight or precise.

You have improved many fifties viewers and written how-to books on
the matter. Do you think it possible for the focusing adjustment to
be improved by you or a user ?


There is a small interocular adjustment, the lenses can

> slide just a bit. This is just based on friction, there are no

clicking

> stops or anything like that. In other words, the construction is

very

> simple and I am afraid there is no room for abuse or rough

handling or too

> much taking apart and putting back again.

Again, do you think that could be modified and improved by you or a
user or would it involve too much work to make it worthwhile ?

> - Illumination: The viewer operates on 3 x AA batteries and a

push-button

> switch at the top. The light is bright and mostly uniform.

Good news ! If I undertand correctly, the LEDs are at the bottom
(base) of the viewer and are pointing upwards into a panel that is
thus illuminated (rather than pointing towards the transparencies) ?


There was

> some concern about dust accumulating at the diffuser. After a few

minutes

> of use some specs of dust were already gathering at the reflector.

Yes, like Mike and others, the first time I saw a rendering of this
viewer, I thought "way too close to film plane". As somebody else
mentioned, Sam's MF viewers have a light panel that is held by
magnets so it can easily be removed for cleaning. Is there any way
of cleaning this light panel without taking the whole viewer apart ?

> A. Focusing. The focusing range is extremely long, however, even

with the

> lenses pulled as far away from the slide as possible, I still

cannot focus

> infinity properly.

Do you see a way that could be corrected by the user or is it a
matter of the size of the viewer itself making it impossible for the
oculars to travel further back ?

> Considering how easy it is to change lenses, one could try to find

and put

> shorter FL lenses. This will give stronger magnification and

better

> centered focusing range.

Well, many were hoping for shorter lenses to be in this viewer.
It's just a shame to get a new viewer and have to modify so many
things.

> B. Interocular adjustment. I
> measured the interocular adjustment of the lenses and it goes from

61mm to

> 65mm. I can only use this viewer at the widest separation of the

lenses

> (65mm) and I still have a problem fusing infinity. I think a

better range

> should have been 65-69mm.

This is something they could have easily consulted on. It is
incredible they would come up with this choice without having
investigated the range of eye separations around the world.
Hopefully, this can be modified.

> Regarding the price, this viewer costs 3x to buy wholesale and I

expect

> its retail price to be 2-3x the price of the STL viewer, so around
> $70-$100. If the adjustments were to my linking, I would have no

problem

> paying this amount for a good viewer like this.

Yes, one would have hoped they had gotten it right this time. Given
the cost of the new viewer is not "the same" as the STL viewer (as
had been previously suggested), have they changed their mind about
discontinuing the STL viewer ?

Francois

> Good news ! If I undertand correctly, the LEDs are at the bottom
> (base) of the viewer and are pointing upwards into a panel that is
> thus illuminated (rather than pointing towards the transparencies) ?

Yes the LDEs are at the bottom but they do not point directly into the
diffuser. The arrangement appears to be similar to the thin panel light
tables, with LEDs instead of a FL tube. The light is very uniform (just
like in any thin panel light table) except for a strip as you get close to
the LEDs but this is mostly blocked from view.

> Is there any way
> of cleaning this light panel without taking the whole viewer apart ?

I don't think so.

> Do you see a way that could be corrected by the user or is it a
> matter of the size of the viewer itself making it impossible for the
> oculars to travel further back ?

The design of the viewer right now makes it impossible (or not easy) for
the oculars to travel further back (or the interocular to be increased)
but, as I mentioned, one could place a spacer behind the lenses, which
will bring the lenses forward (away from the viewer/slide). There is
space for this and still screw the retaining ring in place. A little
trimming might make it possible to increase the interocular.

> Yes, one would have hoped they had gotten it right this time. Given
> the cost of the new viewer is not "the same" as the STL viewer (as
> had been previously suggested), have they changed their mind about
> discontinuing the STL viewer ?

Yes, this is what I have been told. They are planning to keep both
products. Right now I have a large stock of STL viewers for sale.

George Themelis