Is this truly a Letus? at

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Old October 30th, 2009, 03:22 PM   #1
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Is this truly a Letus?

I bought this and it was advertised as a 1st Generation Letus Flip 35mm adapter. It definitely looks similar to the Letus, but the fact that it's made out of some sort of plastic rather than aluminum made me wonder if this is truly a Letus.

There are a couple of minor things that were a little puzzling:
- Dried glue spots on the edges of mirrors (doesn't effect image quality)
- Underneath the lens-mount end I found a "Universal" 2x adapter
- The battery pack was attached with velcro and there doesn't seem any other way you really could mount it
- lots of dried glue around the inside of the camera-mount end
- Black electrical tape around the middle of the mirror assembly.

What do you guys think?
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Old October 31st, 2009, 09:34 PM   #2
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I can't open the linked images - my problem not yours.

From your description, the adaptor is indeed an early generation Letus35 and was the first entry level 35mm adaptor capable of flipping the image, which made a lot of people happy.

These early versions have been described as a work in progress. Much of the hardware was comprised of retasked existing readily available components which could be bought in.

The builder, Quyen Le started building these at an enthusiast level for other enthusiasts.

His objective was to keep costs down for enthusiasts and for replacement components to be commonly available at acceptable costs.

The plastic material is I think delrin, a machineable plastic. It is used in place of metal in many applications and is a valid construction material. Is retains a little flexibility and will not hold cut fine threads well across thin sections.

The black tape is a light excluder and environmental seal.

He used four surface-coated mirrors for the flip path.

There are advantages to surface-coated mirrors, less light loss than prisms. The downside is you have to be scrupulously clean with them and careful not to scratch them or cause them to be permanently etched with fingerprints.

Optical alignment depends on each of the four mirrors sitting perfectly in a perfectly made mount in the flip enclosure. They were retained by border bonds of what is believed to be hot-melt adhesive.

He also chose this adhesive in lieu iof metal fasteners. This was both a blessing as an environmental seal and a curse structurally. It worked against easy home-repair but on the rear shoulder where there was minimal surface contact, the joint was inclined to fail.

Subsquent builds also included small screws on radial centres to retain in combination with adhesive, the front and rear metal tubes on their shoulders.

At the time, the 35mm adaptors were intended to work satisfactorily to SD MiniDV image quality. With care, on the models which fitted "lens-in-camera" style camcorders, pleasing images in the 35mm film camera aesthetic were possible.

Less acceptable results were yielded with the first direct-relay models for the Canon XL and JVC GY-HD*** families due to limitations of the modified Minolta 50mm stills lenses used for relay and a crop factor they introduced which affected apparent resolution and field of view.

The battery pack/switch assembly was one of those retasked components. There was no other convenient way to attach it other than by the velcro.

By "universal adaptor" I am assuming it is a single element lens fitted into the front of the plastic flip enclosure. If it is, this was a simple single element BCX style close-up lens in a threaded rim mount, reversed and used as a condenser.

Last edited by Bob Hart; October 31st, 2009 at 09:39 PM. Reason: error
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Old November 1st, 2009, 11:12 AM   #3
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Thanks SO much for all of the info, that's incredible! I have the JVC GY-HD110u and while I've been able to get it to work I've had some problems getting the ground glass (or perhaps it's the mirrors) completely speck free. So, my results while visually incredible, are marred by this.

I'll keep playing with it and see what sort of results I'm able to get. Otherwise I may need to save and buy a newer Extreme, which I assume yields much better results on the JVC HD110?

Just curious, what might I expect to sell this particular model of Letus for?
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Old November 1st, 2009, 08:00 PM   #4
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How much for a used original anysort of 35mm adaptor, low mileage, original owner - who knows? I think the time is coming when the builder-vendors of 35mm adaptors will come to rely upon their accessory lines like rails, camera supports etc..

So it might be something like trading an old Atari computer with sharpie marks and smileys stuck all over it at a swap meet. Everybody loves it, have fond memories but do not want to take it home.

The HD video-capable stills cams are changing the game at the amateur enthusiast, low budget indie moviemaker level.

I think 35mm adaptors will still have a generation 3 life in a compact form for a while for the smaller 1/4" CMOS handycams and the demographic may change to even younger users and enthusiasts.

My imagining is that at its most basic level, an integrated 35mm groundglass/CMOS memory camcorder made out of plastic will be morphed together with mobile phone bits in Dongguan China and take on the world as "Barbie Moviemaker" or something similar.

That might have a life of about 2 years until obsolete and cheap small DSLR sensors are turned loose and some enterprising OEM does something with them in turn.

As for cleaning the groundglass, to quote a certain New Zealander, it is a mission.

If you look up this clip on YouTube, there are a few hints. Don't go so far as to take the flip enclosure apart. Chances of cracking a mirror are pretty good.

It is helpful to look through the Letus from the back with the eye close to the achromat with the Letus aimed at a strong light so you can see the offending dust motes on the groundglass or front of condenser. Dust on the mirrors is less likely to be seen, if at all as soft grey patches. When cleaning whilst looking through the Letus, the motion of your cleaning tips or art brushes is reversed by the flip optic, so it takes a bit of getting used to.

If you happen to pop one of the cups on the end of the sticks (pillars), pull the cup off the end of the pillar, shove the cup into the hole with a match end or something not sharp, then shove the pillar in with the flat of your thumb until you feel the end pop into the cup. Avoid pushing on the black groundglass carrier panel. It may bend and crack your groundglass or pop the adhesive.

Last edited by Bob Hart; November 1st, 2009 at 08:22 PM. Reason: added URL
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