If you have followed my posts over the last couple of months,
you will know that I have put some 55mm Mamiya lenses on a
TL120. I've been calling the resulting camera my TL120-55.
It is a fixed focus, un-metered camera and is designed to
shoot at f/22.

After I designed a lens board to hold the Mamiya lenses, I
made a "group buy" offer here and several people signed up to
get their own board. I am now aware of at least three
TL120-55 cameras in use. If you would like to have one of
your own, here is your chance.

I had _one_ extra lens board machined. I also have a set of
Mamiya lenses ready to go on it. If you would like your own
TL120-55, send me a mail message off-list and let's talk
about it.

You would have to provide the TL120-1 (or I would have to buy
another one). Where we go from there is open for discussion.
I can provide anything from an assortment of parts to a
tested and working camera, but I don't want to invest a great
deal of time building and tuning if the only interested
person wants to buy parts only.

If I hear nothing, I will finish the board to fit my camera,
do the full focus-adjust and shoot some test rolls. The
resulting board with lenses will be offered over on sell-3d.
________________________________________
John Thurston
Juneau, Alaska
http://stereo.thurstons.us

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

>
> If you have followed my posts over the last couple of months,
> you will know that I have put some 55mm Mamiya lenses on a
> TL120. I've been calling the resulting camera my TL120-55.
> It is a fixed focus, un-metered camera and is designed to
> shoot at f/22.
>
> After I designed a lens board to hold the Mamiya lenses, I
> made a "group buy" offer here and several people signed up to
> get their own board. I am now aware of at least three
> TL120-55 cameras in use. If you would like to have one of
> your own, here is your chance.
>
> I had _one_ extra lens board machined. I also have a set of
> Mamiya lenses ready to go on it. If you would like your own
> TL120-55, send me a mail message off-list and let's talk
> about it.
>
> You would have to provide the TL120-1 (or I would have to buy
> another one). Where we go from there is open for discussion.
> I can provide anything from an assortment of parts to a
> tested and working camera, but I don't want to invest a great
> deal of time building and tuning if the only interested
> person wants to buy parts only.
>
> If I hear nothing, I will finish the board to fit my camera,
> do the full focus-adjust and shoot some test rolls. The
> resulting board with lenses will be offered over on sell-3d.
> ________________________________________
> John Thurston
> Juneau, Alaska
> http://stereo.thurstons.us
>

Hi John,

You mentioned the camera you have completed being designed to shoot
at f22. Does this mean it will only shoot at f22 or is it just
designed to give best results at that setting?

regards,

Harry Calderbank

Harry Calderbank wrote:

> John Thurston wrote:
>> If you have followed my posts over the last couple of
>> months, you will know that I have put some 55mm Mamiya
>> lenses on a TL120. I've been calling the resulting
>> camera my TL120-55. It is a fixed focus, un-metered
>> camera and is designed to shoot at f/22.

. . .

> You mentioned the camera you have completed being designed
> to shoot at f22. Does this mean it will only shoot at f22
> or is it just designed to give best results at that
> setting?

The apertures are fully functional, but focus is fixed at a
point to optimize for f/22.
________________________________________
John Thurston
Juneau, Alaska
http://stereo.thurstons.us

Hi,

If you download this Microsoft Excel spreadsheet and examine it
without modifying the default input variables, you can get a feel for
the various subject depths that John can shoot at different apertures
with his lenses focused at 3.4 meters:

http://home.globalcrossing.net/~zilch0/tools/FixedFocusDoF.xls

The subject depths would be greater and he could use much smaller
apertures if he were willing to reduce the desired resolution. With
his camera setup the way it is, if he adheres to this chart when
shooting, the resulting circles of confusion will support a desired
resolution of 5.7 lp/mm after magnification in the viewer - that's
sharp! Many other factors influence our ability to achieve a
desired resolution, of course, but defocus will not be the limiting
factor as long as he adheres to shooting subjects that fit this chart.

John loaned me a couple of views that he produced with his
55mm-equipped TL-120. They were VERY impressive. The lenses appear
to be well matched and he's got the focus distance set identically as
far as I can tell.

One view is of a deck railing where he had carefully measured the
distance to each of many closely spaced vertical posts. Even though
the posts are painted, the underlying wood grain presents a great
subject for assessing relative sharpness from one post to the next.

When my 78mm SaturnSlide viewer is focused at an image distance of
about 12-inches it yields a magnification of 4.1x. In my opinion,
at that magnification, with his 55mm lenses focused at 3.4 meters,
shooting at f/22, John's creation yields acceptable sharpness as
close as 1.3 meters and spectacular sharpness just beyond 1.5 meters
all the way to Infinity.

The spreadsheet shows that at f/22, with the camera focused at 3.4
meters (11.2 feet), the resulting circles of confusion can support a
goal of 5.71 lp/mm for subject spaces that fit these distance ranges:

f/22.6 --- 6 feet to Infinity
f/19.0 --- 7 feet to 68 feet
f/16.0 --- 7 feet to 38 feet
f/13.5 --- 7 feet to 24 feet
f/11.3 --- 8 feet to 22 feet
f/9.5 --- 8 feet to 18 feet
f/8.0 --- 9 feet to 17.5 feet

Remember that each of these distance ranges can be expanded by
lowering the resolution goal, but if John shoots only subjects that
fit these distance ranges for the apertures shown, I'm certain he cab
bring home some razor sharp wide angle stereo views. (Other factors
that can diminish resolution must be addressed as well, of
course: shutter speed fast enough to arrest camera and subject
motion, for example.)

The other view I examined was of some soccer players on what looked
like a field of artificial turf. A terry cloth head band was lying
on the "grass" in the foreground. I don't know what the actual
distances were in that subject space, but the resulting view was
again, VERY impressive. The combination of the wide angle of view
and more than enough DoF to produce stunning sharpness throughout the
entire scene, coupled with the 65mm "ortho" stereo base is really
nice! John is going to have a good time with that camera!

Mike Davis

Well things have changed and I am going to be going to the NSA Convention
in Grand Rapids. I would be happy to host the Medium Format meeting if
there will be enough people there to make it worth my time. I would also
be willing to be personally responsible for any folios that people would
want to share.

Please let me know ASAP so I can let the convention people know to put a
meeting on the schedule.

Thanks,



David W. Kesner

Hi! John! After buying one lensboard from you, I might be interested to also buy the fully equipped board with the Mamiya lenses on it, after you are through with it! Maybe we can talk offlist about the conditions/and the price you want for it?! Please let me know! Kindest regards, chris
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