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Old December 29th, 2007, 08:38 AM   #1
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looking for the Relay lens

I have a HD200 with a redrock M2 35mm adapter through the stock lens (Fujinon) and everything is going very long...

I was wondering i could use the mini35 RELAY LENS to shorten the whole thing. What is to be attached on the front side of the Relay Lens (back side = JVC mount) ?

Could the relay lens "focus" at less than 3inches ?

If so, may be i could just buy (is it sold alone ?) that relay lens to use on a Brevis, Redrock or other adapters ?
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Old December 29th, 2007, 09:13 AM   #2
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You could buy it and try it but I think you would be on an expensive experiment to only somewhere. You would get it working and possibly very well because the Mini35 relay is very good glassware. However the appliance you improvise may likely be also very long, not quite as long as your current combination, but uncomfortable nevertheless.

The Redrock M2 does not flip the image. The Mini35-300 and Mini35-400 do flip the image. The relay module Mini35 to JVC GY-HD--- camera family is selected to allow the flip portion of the Mini35 to exist between the groundglass and camera.

Therefore the non-flip path from the cam to the M2 would require a longer setback between the groundglass and the cam than the flip path through the prism-mirror path of the Mini35 which folds the image centre axis back on itself. (well almost anyway - using this analogy for simplicity sake). I can't say that the Mini35 relay would not focus at 3" but I doubt it, knowing what I do about my own design and the Letus35 flip for JVC.

I do not know about the Mini35 "compact" relay lens power. The appliance is fairly short. This relay lens may be more powerful to bring the groundglass closer to the camera because the "compact" like the M2 does not flip the image.

If the Mini35 "compact" relay lens is different to the standard Mini35-400, then you might have the answer you are looking for.

The Letus35 developers are cooking up a new direct relay system for the JVC GY-HD and Canon XL camera families.

It might be worthwhile waiting for as the flip portion of their devices is already being used on other 3rd party adaptors and may be an easier hack or even become a custom fit to the M2.

The P+S Technik relay lens will only ever be a hack route unless P+S also decide to offer their relay module with suitable adaptor pieces to complement the M2, SGPRo and others which use the Letus35 flip module and may likely also use the direct relay when it is released.

I would initially think P+S might not compete against the Le Bros on relay optics for third party adaptors, however if they have an excess inventory of parts, and given the imminence of the RED and SI2K, which may hold down future sales of all adaptors, then they might decide to do so to recover some investment in hardware which may have a limited future.

Whitehouse Audiovisual have gone this route with an inventory of "new old stock" CP-Mount Angeniuex 17.5mm - 75mm Super16 zooms they have, which were intially a production run for the CP GSMO camera which apparently was curtailed. They are re-mounting some of these lenses to PL Mounts which makes them economical candidates for the SI2K and the S16 sized usage of the RED. Coincidentally this lens is also called the "compact".

Last edited by Bob Hart; December 29th, 2007 at 09:33 AM. Reason: added text
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Old December 29th, 2007, 11:20 AM   #3
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thank you bob.
so there is really no other idea to use any kind of relay lens... ?
Cinevate seems to prepare one but don't know how many time it could take.
It doesn'nt matter to me if it doesn't flip, the JVC HD200 have a great builtin flip feature.
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Old December 29th, 2007, 01:19 PM   #4
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Quyen Le was using a 50mm Minolta SLR prime lens for a relay lens for the JVC GY HD--- and Canon XL versions. On front of it he installed an unmounted achromatic dioptre to enable the Minolta lens to focus closer on the groundglass.

His path also includes a biconvex lens reversed as a condensor.

Another Letus owner reported getting satisfactory results out of a Nikon zoom with macro function used as a relay with no extra close-up lens or dioptre having to be added on front.

You might get away with using a Micro-Nikkor on a Les Bosher adaptor. Those can focus closer than other Nikons. I don' think they come in f1.8 apertures. How it would perform to the JVC is anyone's guess. Lenses in the ballpark of 35mm to 50mm should work as relay lenses.

35mm might be better as the 50mm Minolta seems to yield about 22mm wide image off the groundglass. I don't know whether the close focusing Micro-Nikkor is available as a 35mm focal length lens.

You might be able to use a f2.8 35mm Nikon with the Redrock's achromatic dioptre on front of it onto the JVC with the Les Bosher JVC to Nikon adaptor mount.

I am really only guessing at all of this.
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Old December 30th, 2007, 07:51 AM   #5
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The 50mm macro f2.8 is really too long even if it can focus on the ground glass. One other thing is that its aperture is 2.8 at infinity and decrease to f4 as you focus at shorter distance...

In fact, the fujinon is set to 20mm while using the redrock, so i think i have to find something like 20mm f1.4.

May be this one would work using the redrock's achromatic dioptre:
http://multimedia.fnac.com/multimedi...8208019137.jpg
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Old December 30th, 2007, 09:38 AM   #6
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I am in uncharted territory here. I have experimented with a Sigma 28mm f1.8 to a 1 chip 1/3"CCD security camera and relay of the 24mm x 18mm motion picture frame can be achieved with that with a forward offset of the lens to enable closer focus.

I did prepare a table once of different focal length SLR lenses and the required forward offsets and distances from lens to groundglass and posted the list here. It is however buried pretty deep and I can no longer find it. My handwritten notes I threw out long ago.

I seem to recall Quyen Le may have also published a comparable list when direct relay of adaptors to the JVC GY-HD--- and Canon XL cams was mooted. I could not dig that up here either.

The posts were on the original AGUS35 thread I think and maybe on the early Letus threads. These are in the "Special Interest Areas" under "Alternative Imaging Methods"

Sorry I can't be more helpful on this.

Last edited by Bob Hart; December 30th, 2007 at 09:40 AM. Reason: added text
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