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Old November 28th, 2006, 11:02 AM   #1
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Location: Woodstock, Georgia
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Relay Lens?

Is there a way I can just get the XL2/XL1 Relay lens? I need one to use with M2 adapter, because the stock 20x lens is way to long and heavy.

If they aren't sold seperately, any direction on how I can make my own?
Solomon Chase is offline   Reply With Quote
Old November 28th, 2006, 08:32 PM   #2
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I am interpolating into your question, the notion that you want to also include a flip function in your M2 as the flip path physically shortens an appliance by turning the optical centre-axis back on itself. If this is not your intention ignore my comments.

Both the M2 and Letus35 XL flip are believed to work to fairly closely to the same in/out targets, - GG image area of approximately 22mm corner-to-corner and 1/3" CCD. Grafting the Letus35 XL and HD100 flip model and the Redrock M2 has been a random thought which has crossed my mind.

Quyen's optical path from GG to camcorder for the XL flip model is :-

GG >> mounted BCX lens as condensor >> mirrors >> unmounted achromatic doublet attached to >> Minolta 50mm SLR camera lens with custom Canon mount >> camcorder.

His objective appears to have been to design around readily available and replaceable existing components which will perform in the GG >> camcorder stage of the path.

His relay arrangement may not work on the M2 unless the entire path and physical placement and spacing of Letus35 components from GG to camcorder replaces the existing M2 path from GG to camcorder.

If the M2 has its own condenser arrangement in the path from GG to camcorder, the condenser lens would have been chosen to complement the camcorder's own lens and an added achromatic dioptre.

If the camcorder's own zoom lens has to be set in the ballpark of 50mm to work on the M2, then there is a chance you might be able to mix and match the M2 and Letus components and achieve a result.

It is not a task I would take on as the M2 path appears to be assembled into a single unitary case which might have to be treated destructively to graft on the Letus components.

If you are not seeking to flip the M2 image but simply to replace the Canon 's own large zoom lens with a shorter relay lens (you'll shorten the camcorder-nonflip combination by about 110mm - 120mm) it may be possible to use Quyen's modified Minolta lens as a complete module.

This would include the components --- Canon XL lens mount on the rear, Quyen's own achromatic dioptre bonded to the front, Quyen's plastic adaptor fitted to front. The entire modified lens is about 58mm from Canon lens mount flange face to front face of the plastic adaptor fitted onto the lens front.

Quyen's plastic adaptor is a fitting which is attached to the front of the Minolta lens as an external sleeve and fits internally to an aluminium tube which is 76mm in external diameter. The internal diameter I do not know, probably in the ballpark of 73mm - 74mm.

On the non-flip Letus35 models, this carries forward to become the GG enclosure and carries the SLR lens mount.

If the M2 tube is of the same internal diameter, you might be able to simply fit up the Letus relay module into it. Most likely however is that the relay lens will not be able to focus on the GG without things having to be cut and hacked to lengthen or shorten to path to match.

If the M2 condenser requires the Letus relay module to be closer to the GG than the M2 tube allows, then the M2 condenser might have to be replaced with the Letus condenser. This might require a custom internal sleeve to be made.

If you are lucky, the unflipped Letus path might be longer than the M2 and you mght be able to make up a sliding sleeve for both tube diameters to enable adjustment if if luckier, one tube diameter might even slip over the other.

It remains likely you would have to hack and cut one or both sets of Letus and M2 components beyond the point where they can be economically restored.

It is not an experiment I would take on without access to precision engineering workshop equipment and the skills to use it.

Please do not take the preceding text as informed comment and most definitely do not let my comments become cause for you to take this task on without more informed comment by others.

I would start by enquiring with Quyen Le if he would make up a relay lens module for you and with the Redrock people for their opinions on the graft.
Bob Hart is offline   Reply With Quote
Old November 28th, 2006, 09:48 PM   #3
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Location: Woodstock, Georgia
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Thanks for the info Bob.

I don't have any interest in trying to flip the image. Just a relay lens so I don't have to use the huge 20x lens!

After reading your comments, it seems you are saying Quyen's minolta relay lens is designed for a longer path to GG? Because of the flipping mirrors adding to it's length?

Could I just mount a wide (18mm-24mm) Nikon, Canon, etc lens directly to XL2 and use that as a relay? I don't know how I would calculate what lens to use though.
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Old November 28th, 2006, 11:47 PM   #4
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Quyen I think may have devised that particular path to suit the readily available components and then built his adaptor layout around this. It seems that there is a fair bit of commonality of components across the flip and non-flip versions.

A flip path enables the enclosure of a given combination to become shorter in length though the optical path remains the same length.

I assumed from your posting in the Letus threads that a Letus/M2 graft was what you had in mind.

You could well buy in a Canon still-camera lens mount to Canon XL mount adaptor, either genuine Canon, or from Les Bosher, his Canon still-camera lens mount or his Nikon still-camera lens mount to Canon XL adaptor.

You could then put a 50mm f1.8 ( or smaller aperture f2.8 ) Canon still-camera lens or Nikon lens on the XL and then fit the M2 acromat in front of that via step rings if it originally fitted to the XL's own zoom lens.

If the achromat is permanently fitted in the M2 and the M2 is normally mounted up directly to the Canon zoom in one piece, ignore my comment and dont try to remove it from the M2.

Then you offer up the unaltered M2 by hand or on an improvised jig to see if it works.

If it doesn't you still have the adaptor to put still-camera primes on your XL.

Doing this might get you in the ballpark of a 22mm diameter scan off the M2 groundglass. You would still have to devise some way of mounting the M2 and XL camera to each other somehow.

A bridgeplate, offset spacers, rods and a lightproof shroud over the gap between the back of the M2 and the achromat on front of the Canon lens would be easiest.

If you can get an accceptable frame area from the groundglass, when finally setting up your permanent distance from GG to achromat, it may be best to make it so that your Canon lens achieves sharp focus on the GG with the lens distance scale in the ballpark of 15 - 19 metres.

Careful attention to maintaining a common optical centre axis through the whole path from SLR lens to camcorder is vital. A poorly precise assembly will work after a fashion but you will be in for a frustrating time getting that last elusive 15% to the image quality you achieve via Canon's own genuine XL lens.
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