I just got back from camping in the Rockies (geez, it was -20 last
night)and found a flurry of posts about putting 55mm lenses on the
TL-120 camera. Rather then make a ton of replies on each posting,
here's a summary of my responses.

Lens Matching

I think those who compare the problems with matching 35mm or single
lensed cameras are missing one big point: we are talking about 55mm
lenses from a Mamiya TWIN LENS reflex cameras. My experience with
Mamiya lenses are that the pair are quite closely matched already.
Mamiya was a standard for professional portrait and wedding
photographers for a long time, and nobody would trust their products
if the focusing lens was not a close match for the taking lens. I had
purchased about 12 pair of Mamiya TLR lenses, and matching was never a
major issue. The only concern was finding a third lens for focusing,
but this was a minor issue. If your taking lens is just a fraction
off, what difference does it make at f:16 or f:32?

That said, wide angle lenses are harder to match generally than
standard lenses. I certainly wouldn't guarantee all Mamimya lenses are
well matched, just that they are a LOT better than other companies,
Yashica for example.

Custom Lens boards

Although I applaud John quest for machining custom made board for use
with the TL-120, it appears the plan may be to mill boards from solid
aluminum stock (perhaps 1/2" thick)and cutting away the access. This
seems like a lot of waste to me, as the only parts that require the
thick sections are the 3 barrel extensions. I think a more practical
approach is to machine the basic boards out of 2 ml sheet aluminum and
make the barrel extensions separate. The barrels themselves are only
there to extend the lenses, therefore can be made of anything (metal,
wood or plastic). This could cut cost down sufficiently, and if
certain models do require different thicknesses, you would merely be
changing the barrel thickness and not the entire lensboard. As
mentioned prior, I cast mine in resin. Not only would this be cheaper,
it would also cut down on the weight.

BTW, has anyone asked is 3DWorld would be willing to sell a quantity
of flat lens boards? If they would, then all you'd need would be cast
barrels.

Anodizing

It is quite simple to anodize aluminum yourself with little expense. I
made an anodizing unit from an old battery charger. Printer dyes work
well. Just go online and search for hobby anodizing and I'm sure
you'll find a plan. If however you get boards from 3Dworld and use
cast barrels, then there's no need to anodize anyway.

Minimum distance using 55mm lenses.

I have mine set at 14' and have room to spare, and I did no machining
of the rear lens or shutter frame. 3.4 m is just over 11 feet. I am
not sure why this has changed.

Just my opinion, not trying to ruffle feathers. I think it's great
there is so much interest in this now, as there wasn't this much when
I tried it!

Sam

> I think those who compare the problems with matching 35mm or single
> lensed cameras are missing one big point: we are talking about 55mm
> lenses from a Mamiya TWIN LENS reflex cameras. My experience with
> Mamiya lenses are that the pair are quite closely matched already.
> Mamiya was a standard for professional portrait and wedding
> photographers for a long time, and nobody would trust their products
> if the focusing lens was not a close match for the taking lens.

You could be right Sam, maybe the lenses are
well matched, but I doubt it would be for the reason you suggest. Even
in a TLR camera, if the fl's were within a couple % of each other, this
is more than acceptable for a camera of this type....but for stereo, not
as good.... testing will reveal how well these lenses are matched in
fl.

Sam Smith wrote:

> Although I applaud John quest for machining custom made
> board for use with the TL-120, it appears the plan may be
> to mill boards from solid aluminum stock (perhaps 1/2"
> thick)and cutting away the access. This seems like a lot
> of waste to me, as the only parts that require the thick
> sections are the 3 barrel extensions. I think a more
> practical approach is to machine the basic boards out of
> 2 ml sheet aluminum and make the barrel extensions
> separate. The barrels themselves are only there to extend
> the lenses, therefore can be made of anything (metal,
> wood or plastic). This could cut cost down sufficiently,
> and if certain models do require different thicknesses,
> you would merely be changing the barrel thickness and not
> the entire lensboard. As mentioned prior, I cast mine in
> resin. Not only would this be cheaper, it would also cut
> down on the weight.

My original idea was to put extensions on the front of a
flat lens board (as you have done). This sent me down
several bunny trails:

Resin cast barrels seemed a good way to go, but how do I
cast resin? How do I get the components shipped into Juneau
without incurring an outrageous barge fee? Unknown
territory; it might be simple or it might be expensive. What
about something else I already know how to do?

How 'bout I just use some tubular aluminum stock and cut it
to length? Nope, can't find any the correct size in Juneau.
It's a great place to live, but it's not known for its
shopping options.

Well, then. How 'bout I have someone machine some material
down to length and bore it out for me? There are three
machinists in town. They have all the work they want for
mining and construction companies. They don't need (or want)
a cash sale off the street.

I've always wanted a lathe. I'll turn the dang things
myself. . . .

At this point, I decided that what I really wanted was a
camera with which to shoot. I didn't want to learn how to
cast resin, run a lathe or forge aluminum. If I had to do a
drawing and write specifications for a job to be sent to a
machinist, I decided I may as well try to do a drawing and
specification which could be used more than once.

That's how I ended up where I am. No, it's not the lightest
weight solution nor is it the least expensive. But I think
it's no more expensive for me than buying a lathe or hiring
someone in town to turn some stock.

If someone wants to group-buy some lens boards and have some
spacers cut, drilled and tapped to fit them, I like to buy a
set. Anyone?

> Just my opinion, not trying to ruffle feathers.

Non ruffled here, Sam. I lost all my feathers years ago!

--
John Thurston
Juneau Alaska
http://stereo.thurstons.us

--- In MF3D-group@yahoogroups.com, John Thurston wrote:

>
> My original idea was to put extensions on the front of a
> flat lens board (as you have done). This sent me down
> several bunny trails:
>
> Resin cast barrels seemed a good way to go, but how do I
> cast resin? How do I get the components shipped into Juneau
> without incurring an outrageous barge fee? Unknown
> territory; it might be simple or it might be expensive. What
> about something else I already know how to do?

I fully understand not wanting to go into new ideas like molds and
casting. I used Alumilite, which I imported from the US from
Kalamazoo. The website is: www.alumilite.com. It is rather inexpensive.

>
> How 'bout I just use some tubular aluminum stock and cut it
> to length? Nope, can't find any the correct size in Juneau.
> It's a great place to live, but it's not known for its
> shopping options.

I was thinking more in the lines of locating a hobby machinist who has
a CNC mill, someone like Allan Lewis for example. A basic CADD program
could be converted to CNC code, and the basic flat 2ml stock should
only require a couple of tool changes. Seems there were a few
3Dhackers out there in the past, although some like myself have
unfortunately moved on.

One other possibility of finding someone (besides the camerahackers
group) is the cameramakers group at:
http://tech.groups.yahoo.com/group/cameramakers/

It may be there just aren't any options as convenient as the local
machine shop. My own efforts to get a series of complete W/A units
ended in frustration, so any successes you have will truly be
appreciated John.

Thanks,

Sam