|January 6th, 2009, 08:18 PM||#1|
Join Date: Sep 2005
Location: New Hampshire
Can I convert a LetusXL for use with a Canon HV30?
I have a LetusXL that I purchased about 6 months before the extreme came out. This adapter, everyone well knows, connects directly to the Canon XL series cameras. I was wondering of there is any way to adapt it to mount to the Canon HV30?
Any advice would be greatly appreciated.
|January 6th, 2009, 10:06 PM||#2|
Join Date: Dec 2003
Location: PERTH. W.A. AUSTRALIA.
Yes, with difficulties.
Anything is possible but whether it is cost-effective is another matter.
The rear tube which carries the Minolta lens and its attached achromat would have to be dismantled from the rear of the filp enclosure. I call this tube a bridge tube or bridge piece.
Typically, this tube was slid over a shallow shoulder which is machined into the flip enclosure. Early versions were attached with a semi-hardening adhesive. There were early instances of this bond failing. Your version may have some additional screws on radial centres there.
The depth of this shoulder is very small. You will wisely not rely on this for mechanical support of the adaptor and stills lenses.
The tube however may be difficult to remove as the glue has had good time to mature. Below is a link to show how it can be done. It will require a small hole to be drilled in the tube right over the shoulder as seen in the video.
Now you can set about removing the Minolta lens from the tube. It will be fastened to the rear of the tube by a plastic insert. This will be secured by radial screws and semi-hardening adhesive.
From this point on it gets interesting and the skills and equipment of a machinist will be needed for best outcomes.
The achromat on front of the Minolta is comprised of two bonded unmounted elements. This achromat may work on your camera, maybe not. It is also matched for better or worse to a reversed single element biconvex mounted lens inside of the adaptor.
This element is mounted in a threaded metal rim and is itself a single element close-up lens, except in this instance it has been reversed to function as a condenser. The thread on the rim is not used to attach it to anything. The rim is an interference fit into a shouldered hole in front of the flip enclosure.
It may be possible for you to carefully cut away the semi-hardening adhesive which has been used to attach the achromat to the front of the Minolta lens, remove and use this achromat for your new camera.
It is unmounted, so you would have to devise a way of mounting it either to your camera front or to the rear of the flip enclosure.
The most likely method will be to make up another insert of a similar style as the Minolta insert, to fit into the rear tube. The achromat would be mounted into this insert inside of a shouldered hole.
Depending on how much setback your camera needs with this achromat in the path, you may need to make another longer tube or shorten the one you have.
You will probably find that camcorder zoom range from about 40mm - 50mm will bring the groundglass frame close enough so that the edges do not vignette the camera image.
It is likely that this combination may cause edge or corner softness and you will have to play around with just how close or far away from the front of the camcorder lens the achromat has to be for best compromise.
As close as possible is usually best, but not always.
You will have to take exceptional care to not let the edges of the unmounted achromat touch the front element of the camcorder lens otherwise it will be totally ruined.
Wrap the outer rim and sharp corners of the achromat with a trimmed-down layer of gaffer tape when offering the achromat up to the camera by handholding.
The Letus XL worked in this manner when I handheld it up to a Sony HVR-Z1P which had a Century Optics achromat from my own AGUS35 fitted.
I no longer recall whether it was the 4+ or 7+ and I am not about to rip it all apart again to find out. Both powers will possibly work.
They are convenient in that the elements are mounted in a rim which has a 58mm lens filter thread. If an achromat can be mounted directly to your camera, then all you need to worry about is supporting the camera and adaptor together in correct alignment.
On your camera, it may not be possible to install these mounted achromats close enough to the front element of your camera lens, especially if you have to use shouldered stepdown or step-up rings instead of concentric ones which maintain a common flange face when assembled.
The Letus special EX1 achromat for the Extreme seems to be in the ballpark of about 5+ power.
Getting the camera and Letus Extreme lined up and stably supported will be a challenging task, especially if you do not remake the bridging tube.
A baseplate and rods kit would do it. Cine-city in India have a good one for this task. It comprises a camera baseplate with several tripod screwholes of both sizes which broadens your tripod options for your camera. I can only speak for the version they sell for the JVC GY-HD100. If you choose this one you will likely need to make a packing piece to go between your camera's base and the Cine city baseplate.
There is limited but fairly generous lateral and vertical adjustment available for trimming your optical axes if you mount the camera and Letus separately and do not attempt to make a tubular bridgepiece as well.
You would have to make up at least one but preferably two plates cut from MDF (which is a bitch to work and finish with any precision), phenoilc board, machinable plastic (delryn) or even a piece of nylon cutting board. If you are rich, you could have them machined from aluminium plate.
These plates will have a large clearance hole for the front and rear tubes to pass through.
Once the rod holes are correctly lined up and the groundglass screen is correctly square within a zoomed-back camcorder view, then these plates could be glued to the front and rear of the flip enclosure. I found that toluene based contact adhesive was adequate.
Here is a web address to a Letus XL being dismantled.
YouTube - LETUS35 FLIP FOR XL MAINTENANCE AND BEYOND
This should give you a few clues. Ignore the motor. It is not the original Letus vibrator motor but a larger CD player tracker motor with cut-down shaft. It barely fits in available space.
You will observe the single-plate rods mount I made fitted on front of the flip enclosure. The better method will be to make two. The rear one will have to be taller than the front.
Don't cut the rod holes out of the rear one until you have established the correct orientation of the groundglass screen squarely in the camcorder view. If you work strictly to measured centres, you may find the rods holes to be incorrect.
You could measure and cut to centres but you may find there might not be enough adjustment available at the Cine city baseplate adaptor to restore the optical axes to correct alignment.
You could make the rear plate a two-piece adjustable arrangement. Vertical slots in one piece and horizontal slots in the other or more simply, oversize clearance holes and wide washers.
My personal preference would be making a machined Letus Extreme style tubular bridgepiece which threads into the camcorder filter thread and contains the original unmounted Letus achromat ( if it has been tested and works ) in a shouldered hole inserted from the front.
If you try to use clamping screws on radial centres Letus Extreme style to fasten onto the rear shoulder of the flip enclosure, this won't work as the shoulder is too shallow and the Delryn material is too flexible and will pull away.
You could machine a small metal ring to slip inside the shoulder, drill and tap radial screwholes into it and fasten the outer tube through clearance screwholes in the Delrin shoulder to the innner ring.
The remains a chance that the holes in the Delrin shoulder will pull through if you load them as there simply is not enough material in the shoulder for any but tiny screwholes.
You could drill and tap axial screwholes into the rear face of the flip enclosure to attach a flanged bridgepiece, however you would risk disrupting or breaking the mirrors and loose swarf ending up in the enclosure. It is not a place I would care to go.
Hopefully this will help you.
Last edited by Bob Hart; January 6th, 2009 at 10:22 PM. Reason: added text
|January 7th, 2009, 12:49 PM||#3|
Join Date: Sep 2005
Location: New Hampshire
WOW! You certinly know this product. Inside and out. I'm very hesitent about taking it apart. I was kinda hoping for some type of mount/adaptor solution. Thanks for you very descriptive reply. Perhaps one day, when I have a new Letus, I'll come back to this post and take the letusxl apart.
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