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Old February 8th, 2008, 03:33 PM   #1
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Mini 35 back focus adjustment?

I own Canon H1 and Mini 35 adapter,

have not done too much shooting yet, like the image so far, yet it seems a little soft.

I took it for granted that it's set focused on ground glass, so is it in fact true,
Is there any adjustment possible to focus precisely on the ground glass?
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Old February 9th, 2008, 12:14 AM   #2
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forgot to mention it's 300 series and it works great for HDV, i just don't close
past F4
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Old February 9th, 2008, 03:31 AM   #3
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Anyone has a manual for 300, please?
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Old February 9th, 2008, 09:35 AM   #4
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Hello,

Before the the e=image gets to the GG there is no focus parameter but the lens it self.
once the image gets to the relay lens that mounts on your XL-H1 it has a ring that turns to focus the relay to the GG.

I got the same setup....Mini35 with XL-H1 and I get a great image. i'm happy with it.

Now, you will get a soft image all the time, this is nothing compare to Video. The key in this set ups is to use fast speed lens and light up like a DP for 35mm would.

Also most of the stuff are done in post...the CC with this set ups are not like video, you always have to work more in the contrast and obviously the colors.

By the way, the only manual that is available is the 400 series....but there is not a big difference in between this two units, is just the spinning GG inside.

Take care,

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Old February 9th, 2008, 09:38 AM   #5
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Oleg.


I may be wrong here so don't take too much notice of me.

I think the Mini35 Series 300 relay lens is the same arrangement as for the 400 series.

The 400 manual can be downloaded from the P+S Technik website as a .pdf file.

The relay lens has two control rings. The aperture ring has numbers on it and has grips machined into the surface. It is the rear ring, closest to the camcorder.

The focus control ring is smooth. It is closest to the Mini35 box. It is also locked in position by a very small allen screw which is set deep in the ring itself.

This has to be loosened to allow the ring to turn. Once the backfocus is correct, this screw is tightened again to secure the ring from moving off focus.

Don't loosen the flat blade screw in the focus ring which is nearby the allen screw and level with the surface of the ring.

To set backfocus, turn the iris of the SLR lens you mount on front of the Mini35 to about f11 or f16.

Set relay lens aperture to wide open.

Do not switch groundglass motor on.

The "grain" of the groundglass should be visible and fairly sharply defined.

If the image is too bright for the camcorder to see the "grain", point it at light which is not so strong.

Adjust the relay focus until the "grain" can be seen sharpest.

Lock the focus ring with the allen screw.


Better brains and ability than mine may comment here so take notice of them.
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Old February 9th, 2008, 10:48 AM   #6
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Carlos, thanks a lot,
I really enjoy my 300, plan to get some more Nikon, Zeiss lenses

Bob thank you very much, for detailed explanation, really appreciate it,

Found a very small allen screw which is set deep in the ring itself - I have to find right tool, do you happen to know what size is it?

Best regards, good luck on your auction.

Oleg.
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Old February 9th, 2008, 11:53 AM   #7
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Not a problem...good luck !

Take care !

Carlos Quinones / www.imdb.com/name/nm2876243/resume
carlos@itswrittenproductions.com

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Miami, Florida

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Old February 9th, 2008, 05:51 PM   #8
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Oleg.

I'm not sure if this is the correct one. A 1/16" allen key seems to get it loose but it feels a bit too large like it fits only in the end of the hex hole instead of going right in. It is enough to be able to secure it.

Fortunately little tightness seems needed to secure the backfocus ring from moving. It probably should not be over-tightened anyway.

P+S are thorough enough designers that the screw-end may bear down onto a floating friction piece and not directly onto the barrel of the lens body or the surface the screw-end binds onto may be very hard material.

There seems to be no binding or balking as the friction comes off so that is my guess.

I could not find the correct size in the Mini35 manual.

The relay lens is said to be perfectly sharp to wide-open aperture.

Other forums have suggested that for 1/3" imagers like the Canon, Sony JBC etc., f5.6 or near to it is a sweet spot for camcorder iris settings for the camera's own lenses. Tighter apertures begin to incrementally introduce an artifact referred to as diffraction. I don't know if this has been engineered out of the P+S relay lens. Only they would know. It is more practical not to theorise and experiment with settings instead.

Last edited by Bob Hart; February 9th, 2008 at 06:01 PM. Reason: added text
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Old February 10th, 2008, 03:58 AM   #9
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Bob, thanks again, will look for the right tool, I am on H1 and 300 series, there is no camera iris control, and on Nikopn lens I prefer to shoot at F2, to be closed slightly and have a shallow DOF,
Thanks again..
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