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Old August 3rd, 2009, 04:06 PM   #1
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1/3" relay lens solution?

any news on possible solutions?
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Old August 4th, 2009, 12:32 PM   #2
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What camera type are you using?
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Old August 4th, 2009, 02:21 PM   #3
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I'm using jvc hd100.
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Old August 4th, 2009, 10:19 PM   #4
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As far as I know, the R&D is still being done for relays for 1/3" cameras.

A passable hack for the Letus Extreme but not outstanding, is to use a Les Bosher or Mike Tapa JVC GY-HD100 to Nikon F-Mount lens adaptor then use a Nikon lens in the ballpark of 35mm f.14 to 50mm f1.4 for relay. With a 50mm you will encounter the same crop factor as with the original direct relay models which used a Minolta 50mm prime.

Stills lenses are cheaper than the genuine Fujinon so the detail performance cannot be expected to be the same, however a 1/3" imager shoots through the sharper centre of the stills lens so you get a bit back.

Stills primes are also not designed to compensate for 3xCCD/3xCMOS sensor arrangements which use prisms, so you can expected chromatic abberation on high contrast edges in the image.

You will observe this in a vertical direction from a stills lens as distinct from all directions with a genuine compensating lens which may still have some CA present.

The hack requires you to make or to have made, a bridgepiece to go on back of the Letus Extreme with a 0.7mm pitch filter thread of 52mm to screw into the front of the more common Nikon lenses.

Most lenses will have a moving front element which means that the Letus Extreme must be free to move back and forward with relay focus adjustments. The usual trick is to leave the front support loose on the rods, until a ballpark relay focus is found, then the support on the rods is tightened. Very fine adjustments will remain possible.

When assembling the adaptor and camera to the rods, the alignments must be spot-on otherwise the lens focus adjustment will become loaded and bind.

By comparison with the genuine Fujinon lens, there is little if any to be gained except for the combined appliance being shorter.

If you look up "Roiding the Extreme" in the Letus threads here, you will find more discussion.

Last edited by Bob Hart; August 4th, 2009 at 10:22 PM. Reason: error
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Old September 25th, 2009, 05:08 AM   #5
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Theoretically a c-mount lens should do. I have tried nikkor 35 mm enlarger lenses, and the distances needed were too large to profit. ( Canon xl sytem)
I wish I could try some c-mount lenses from older super8 camera's, leicina's etc. probably there will be some problems since the 'resolution ' from super8 was in general lower than hdv
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Old September 25th, 2009, 11:58 PM   #6
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With the c-mount for 8mm film cameras, you may find you experience a vertical chromatic aberration above bright objects same as with the stills primes. Lenses for 3 x CCD cameras have some optical tricks designed into them to reduce or eliminate CA.

Also I think the JVC flange to focal plane in-air may be in the ballpark of 37mm. Somebody who knows will hopefully correct me here. The flange to focal plane of c-mount lenses for 16mm film cameras is 17.5mm. I imagine for 8mm it would be the same or maybe even less - better advice from those who know to be added here too.

If you set the c-mount lens about 5mm forward of its normal flange position, it would focus closer without an achromatic dioptre in front of it but would probably still be too close to the prism face on the JVC. My experiments in trying to hackfit stills prime lenses for relay into the SI2K without an achromatic dioptre yielded poorer results than using the correct flange distance and using the achomatic dioptre provided by the 35mm adaptor vendor.

Last edited by Bob Hart; September 26th, 2009 at 12:05 AM. Reason: error
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Old September 26th, 2009, 03:53 AM   #7
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I know, that's why I first experimented with photo enlarger lenses, since they are designed to project flat surfaces (negatives) to other flat surfaces ( paper).
I have used the nikkor's enlarger lenses before as good macro lenses back in the days of analog still photography but I found them not suitable as relay lenses, for one due to the needed distances and indeed some c.a. My solution was to rent a p&s rig for the shoots .
Since I no longer have need for "cine" dof and images, i stopped experimenting.
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Old October 1st, 2009, 11:59 PM   #8
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The Letus 1/3" bayonet relay became available over a month ago.
Letus 1/3" Relay*::*Letus Relay Lenses*::*LetusDirect
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Old November 7th, 2009, 08:40 AM   #9
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Has anyone tried the new Letus 1/3" Relay (Full Frame) on a JVC HD series camera? I'm finishing up one web series and would love to impliment something like this on the next one I'm doing.
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Old November 15th, 2009, 08:06 AM   #10
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Letus relays ...

Wish they made these for other systems. I have a SGBlade which is very good and could use a 1/2 with my EX3.
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Old November 16th, 2009, 09:09 PM   #11
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Chances are the 1/2" relay would work. However, there would need to be an adaptor ring designed for the junction between the front of relay lens and the SGBlade.

It would be worthwhile enquiring with the manufacturer of the SGBlade Wayne Kinney. I would be surpised if he has not already experimented and can tell you if it works or not.

I understand that he may still use a slightly larger area of image off the groundlass than the Letus Ultimate, so the aquired image via the direct relay lens should be within a safe area of the SGBlade image.

I understand Dennis Woods was working on a high quality short-throw zoom relay for the Brevis to enable trims of the frame across camcorder format types with a single lens. So it might be worthwhile to ask him if he does not respond here.

Last edited by Bob Hart; November 16th, 2009 at 09:13 PM. Reason: error
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