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Old June 22nd, 2007, 02:57 PM   #1
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Lens mounting to loosely

I have the Letus35a, with the flip lens ring that accepts Nikon mount on one side, and Canon on other. When I started my shoot last weekend, the Nikkors were mounting snuggly. By the end fo the shoot, they mounted loosely and spun of the mount when I was trying to focus.

Anybody had this issue, and what is fix.
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Old June 23rd, 2007, 01:39 AM   #2
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Chris.

That mount has no compression spring behind it like the Nikon genuine mount, so as wear on the flange face and lug faces occurs, a clearance will be created.

One suggestion has been to bruise or compress the metal on the inside circumference of the lugs to displace raised metal into this clearance to restore the tightness of the fit.

This could be achieved by simply pressing hard on the inner circumfence towards the rear contact faces with a screwdriver tip, very gentle cold chiselling or pinching with side cutters to raise some burrs, none of which are a particularly elegant engineering solution and about as professional as dragging your camera along on the ground on its base behind you with a string to get that POV of following dog on a lead shot.

More importantly, the solution will only be as enduring as the time it takes to wear the newly raised metal down.

The dedicated Nikon-only mount is the better solution however there is another fairly crude method I used with the reversable mount which involves filing a bit of the longest mount lug away and drilling and tapping a screwhole on a radial centre to protrude in behind one of the lens lugs when the lens is turned fully home. The screw is not turned fully home to compression but only so far as to latch in behind the lens lug to stop the lens from turning.

The hole has to be drilled so that the screw end comes down to stop the lug from turning back but rearwards enough that the screw end does not come down on the secondmost rear rim of the lens.

Send me a bounceback email address and I will attach some pics in return. I don't have the software to resize .jpg stills to post here.

Last edited by Bob Hart; June 23rd, 2007 at 01:41 AM. Reason: error
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Old June 24th, 2007, 09:54 AM   #3
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I have managed to get the .jpgs up on another site. Details as follows :-

http://www.savefile.com/files/836553

http://www.savefile.com/files/836576

http://www.savefile.com/files/836584

http://www.savefile.com/files/836596

When you get linked to the savefile page, you may have to scroll down until you get to the download button near the bottom of the page, orange in a dark band.

All above are for images of a Letus35 reversable mount mod to secure Nikon lenses from turning in the mount while focussing. The squareheaded screw in the two o'clock position is the one to take notice of.

The roundheaded screws on the case are extra support for the mount. The roundheaded screw in the front of mount is simply a plug for a wrong hole and should be ignored.

The 12.5mm rods and baseplate are from an unbranded teleprompter mount for Canon XL2.

The front support for the Letus 35 is made from phenolic board. It has since been modified to be hard fastened to the Letus35 and clamped to the rods by a single wingnut and stud rather than the two-lockscrew method visible in this image set.

Files on the Savefile site time out after a fixed period of inactivity, so they may disappear with the passing of time.

My ill-advised intrusions into the entrails of the Letus35 flip for XL can be found here :-

http://www.youtube.com/watch?v=yugfv4ZVXgg

How the screw locks the Nikon lens in place is illustrated in the first part of the clip where it is loosened to release the lens.

Hopefully of some use in solving your problem.

Last edited by Bob Hart; June 24th, 2007 at 10:20 AM. Reason: errors
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Old June 24th, 2007, 03:06 PM   #4
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Bob- Thanks.

I did a brief work around as follows, and I got an email from Quyen too, which suggest applying a hammer. Thanks for your input. Looks like that is the next step for me when my immediate fix starts giving way.... I did find out from Quyen that new reversables sell for $25, so I may just buy a mount for each lens, and not wear them down by constant removal.

Here is fix I explained by Queyen:

Take the mount and lay it flat on a hard and flat surface, Nikon side up.
Use a flat screwdriver and a small hammer to tap on the left side of the 3
flanges. Don't use too much force. It will fit the lens snuggly, thanks.

Quyen

Explanation of one I employed temporarily:


Queyen:

I thought about doing that, and it was an alternative, but I've tried another fix since I sent the email. I have a wide roll of packing tape, a piece of which covered virtually the whole flange face of the mount. I made sure it stuck well to the surface, then trimmed away everything except what was on front mount. Created a very thin surface that was just enough to firm things up.
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Old June 25th, 2007, 01:22 AM   #5
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Quyen's method is not as inelegant as it may sound, but care and delicacy is needed otherwise you could chisel a piece off one of the lugs.

The method bends the trailing portion (ainti-clockwise end) of each lug face rearward to create a helicoid face which works by a wedging action to bind the lens tight, more or less how the Nikon spring works. Treat the wrong end and you won't get the lens to fit on.

This is still only a frictonal retention. The Nikon spring is mainly there to prevent lens movement whilst enabling a smooth mounting action. Positive retention on the genuine Nikon mount is by the pin and release button.

Even the P+S Technik Mini35 found be found wanting in this area. There is a latch pin and release button but it is liable to bend and become difficult to release. Les Bosher's adaptor pin release can also become difficult.

During my brief stare into the Mini35 innards, I did not see a Nikon spring but there may be an alternative in there somewhere.

Nikon's own pin release system is housed in the camera body where space is available. With the 35mm adaptors, available space is available only within the mount itself and extremely limited, a very difficult task. I tried and gave up and kept the screw method.
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