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Switar RX preset lenses on a H8 RX-4


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#1 Michael Carter

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Posted 03 April 2006 - 02:25 PM

Three Switar H8 RX preset prime lenses on a H8 RX-4 camera work great for R8mm, but, could the lenses be adapted to a normal 16mm camera? They do not focus as is on a H16 RX camera.

Thanks.
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#2 Tim Carroll

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Posted 03 April 2006 - 03:14 PM

Three Switar H8 RX preset prime lenses on a H8 RX-4 camera work great for R8mm, but, could the lenses be adapted to a normal 16mm camera? They do not focus as is on a H16 RX camera.

Thanks.



I would be concerned that they would not cover the 16mm frame. The regular 8mm frame is half the size of the 16mm frame, and I would be concerned that they would vignette pretty badly. You could certainly test them and find out.

-Tim
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#3 Michael Carter

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Posted 03 April 2006 - 07:52 PM

I would be concerned that they would not cover the 16mm frame. The regular 8mm frame is half the size of the 16mm frame, and I would be concerned that they would vignette pretty badly. You could certainly test them and find out.

-Tim

Rear element diameter is 10-11mm wide; that is twice the size of a 16mm wide angle lens and the same as some other C mounts for 16mm cameras, but not as wide as some telephotos.
These lenses are "C" mount lenses and are not the usual "D" mount types.
They don't focus on a RX or a nonRX camera so I have no way to test them.

Edited by Michael Carter, 03 April 2006 - 07:54 PM.

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#4 Boris Belay

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Posted 05 April 2006 - 12:18 PM

Hi Michael,

Interesting problem... The back focus distance is different on the H8RX and on the H16RX. For one thing, the turret on the H8 is slimmer than that on the H16.
Besides the possible vignetting mentioned by Tim (lenses optically designed for an 8mm. coverage), I don't know what other problems you may run into.
Regarding focusing, I would begin by unscrewing the lenses little by little while trying to focus on an infinity point. Since the H16 has a larger back flange distance, you may find the point where they will focus with that method. Start with the longer focal lengths as they will be easier to focus. If you get a focused infinity, then try other focus distances.
Let us know the results !
B.
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#5 Leo Anthony Vale

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Posted 05 April 2006 - 02:18 PM

Rear element diameter is 10-11mm wide; that is twice the size of a 16mm wide angle lens and the same as some other C mounts for 16mm cameras, but not as wide as some telephotos.
These lenses are "C" mount lenses and are not the usual "D" mount types.
They don't focus on a RX or a nonRX camera so I have no way to test them.


---The rear element diameter is a red herring.
It has nothing to do with coverage, it's related more to maximum f/stop and amount of light transmitted.

I can find nothing that indicates that H-8s use any mount rather than D-mt.

If yours really do have C-threads, chances are it still has a flange focus of around the same as a D-mt.

Which is 12.29mm vs. 17.526mm for the C-mt.
So your displacement is over 5mm. For a 5.5mm lens you're getting close to 1:1 copying.

Try moving a transparent chart closeer and closer to the lens instead of moving the lens out.

---LV
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#6 Clive Tobin

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Posted 05 April 2006 - 08:38 PM

I can find nothing that indicates that H-8s use any mount rather than D-mt....


It is well known that the H8 non-reflex cameras use D mount, and the H8 Reflex cameras use the H8RX mount, which is the same threads as C Mount but a different flange distance. This causes a lot of confusion on Ebay and elsewhere. There is some mention of this on my Identifying Your Bolex writeup, now with two pages of pictures, on my website http://www.tobincinemasystems.com .
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#7 Michael Carter

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Posted 06 April 2006 - 09:54 AM

The 36mm lens will focus on a lace curtan 2 feet away when screwed in all the way and set on infinity.

When focused at infinity, viewing houses far away and screwed out all the way it is more blurry than when screwed in all the way. It needs to get closer, not farther away. It will not focus at infinity, looking out the window.

The frame is fully covered on a H16-T using a H8-RX 36mm preset lens. Good for close ups.

16mm c mount lens 25mm RX didn't focus near or far in or out on a H8RX.

Deep set Bolex lenses don't fit at all.


I suppose one could make 8mm films with it.

Or, if really dedicated, have it converted to DS8mm.

Edited by Michael Carter, 06 April 2006 - 09:55 AM.

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