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Author Topic: Centre Filters  (Read 3687 times)
zzzone
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« on: January 16, 2007, 09:39:12 AM »
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Hi

During my short time with the Horseman SWD2, you needed to set the 35mm Rodenstock lens at about the 4/5m lens mark to achieve focus at infinity!!  Something seriously not right and it is boxed up to go back now the CamboWDS has arrived.

Something that concerned me more with the Rodenstock when tested was that optimum infinity focus (at wide open) was not achieved at the same lens mark!!  When I had the loan Cambo before with the Schneider 35mm lens I did not undertake a rigorous test but I shall be doing that with the new kit that I have purchased.

One thing struck me was whether the centre filter used on the Rodenstock lens could have been of any influence on the plane of focus at infinity?  Furthermore how many of you with Alpas, Cambos etc with 35mm and wider lenses use centre filters or use Photoshop should the vignetting not be complimentary?

Regards Steve
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pixjohn
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« Reply #1 on: January 16, 2007, 11:19:19 AM »
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I have a center filter for my Schneider 24xl lens. I do not  use the filter that often, since I  use the Gain Adjuster to correct issue with my leaf aptus 75. The Gain Adjuster correct the centerfold line and also corrects any falloff from the lens.  As to the the center filter causing any problems with focusing at infinity, I would find that impossible. I also notice problems with focus on my 47xl at infinity. If I move the focus back a little from infinity I get a sharper image. I even inquired with Cambo and they told me the same thing.
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ericstaud
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« Reply #2 on: January 16, 2007, 12:09:37 PM »
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"During my short time with the Horseman SWD2, you needed to set the 35mm Rodenstock lens at about the 4/5m lens mark to achieve focus at infinity!! Something seriously not right and it is boxed up to go back now the CamboWDS has arrived.

Something that concerned me more with the Rodenstock when tested was that optimum infinity focus (at wide open) was not achieved at the same lens mark!! When I had the loan Cambo before with the Schneider 35mm lens I did not undertake a rigorous test but I shall be doing that with the new kit that I have purchased."

I have an Alpa 12SWA.  The adapter for the H1 mount came with shims (super-thin gaskets really).  I had to remove 1/10th of a millimeter from the shimming to acheive critical focus.  Before that, the 35mm lens would focus about 50' out when set at infinity.  I did have one lens, out of 4, not focus properly.  It was exchanged by the dealer.

Aside from testing each lens carefully when I buy it, it is also necessary to test each MFDB before assuming the markings on the lens will give me good focus.  I had one P45 that was 1/10th millimeter different than the other P45 and four Aptus 75's I've used.  With my current shimming, that P45 would severly back-focus if I went by the numbers on the lenses.

I wish I could unmount some of my digitars to use on lensboards for other view cameras,  but the tollerences for the focus mount are just too small.  I remember when you would rent a lens and they would just throw it on any lensboard you needed for your 4x5 camera.

"one thing struck me was whether the centre filter used on the Rodenstock lens could have been of any influence on the plane of focus at infinity?"

Only filters BEHIND the lens change the focus plane.  Center filters should pose no problem.
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rainer_v
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« Reply #3 on: January 16, 2007, 02:24:39 PM »
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the rodenstock helical mounts  have three little screws on their distance rings. if you open them a little bit you can move this ring and adjust it exactly too infinte. takes 5 minutes with each lense.

i dont use center filters on my 28 + 35 hr lenses. the fall of is compensated by white shading, which i allways do.
« Last Edit: January 16, 2007, 02:25:34 PM by rehnniar » Logged

rainer viertlböck
architecture photographer
munich / germany

www.tangential.de
zzzone
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« Reply #4 on: January 16, 2007, 02:33:20 PM »
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I am sorry but I have not explain the issue well enough!!

Infinity focus in the centre of the Rodenstock lens was achieved at approximately the 5m lens mark whereas optimum focus for the image at the edge was achieved at an even shorter lens mark.  This must imply that the plane of focus for a given lens setting is not planar for this lens!!??

Regards Steve.
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pixjohn
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« Reply #5 on: January 16, 2007, 03:10:18 PM »
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Simple, sounds like the lens is messed up!
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yaya
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« Reply #6 on: January 16, 2007, 03:14:16 PM »
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I am sorry but I have not explain the issue well enough!!

Infinity focus in the centre of the Rodenstock lens was achieved at approximately the 5m lens mark whereas optimum focus for the image at the edge was achieved at an even shorter lens mark.  This must imply that the plane of focus for a given lens setting is not planar for this lens!!??

Regards Steve.
[a href=\"index.php?act=findpost&pid=96026\"][{POST_SNAPBACK}][/a]

Steve, I think that instead of banging your head against the wall, it'll be wise to call Cambo, set a date, get in the car with the back/ camera/ lenses, drive to Holland and spend a few hours with Rene Rook, adjusting everything.
You will come back with a working system, end of story.

Yair
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Dustbak
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« Reply #7 on: January 17, 2007, 01:02:27 AM »
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Steve, I think that instead of banging your head against the wall, it'll be wise to call Cambo, set a date, get in the car with the back/ camera/ lenses, drive to Holland and spend a few hours with Rene Rook, adjusting everything.
You will come back with a working system, end of story.

Yair
[a href=\"index.php?act=findpost&pid=96034\"][{POST_SNAPBACK}][/a]


I only hope Steve doesn't live in the US. That would be a very long drive
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pixjohn
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« Reply #8 on: January 17, 2007, 02:05:29 AM »
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Yair, that a great answer! I only wish I could hop a plane, land in Tel Aviv and drive to Herzlia  with my Aptus 75 and Mac Book Pro with LC 10 and see if Leaf can get a clean file with out all the software work arounds.

Quote
Steve, I think that instead of banging your head against the wall, it'll be wise to call Cambo, set a date, get in the car with the back/ camera/ lenses, drive to Holland and spend a few hours with Rene Rook, adjusting everything.
You will come back with a working system, end of story.

Yair
[a href=\"index.php?act=findpost&pid=96034\"][{POST_SNAPBACK}][/a]
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yaya
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« Reply #9 on: January 17, 2007, 02:37:17 AM »
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I only hope Steve doesn't live in the US. That would be a very long drive
[a href=\"index.php?act=findpost&pid=96108\"][{POST_SNAPBACK}][/a]

From Steve's place to Kampen is probably not more than 7-8 hrs drive or maybe quicker by plane:-)

I know several architechture photographers who ended up taking the kit to the camera factory (Cambo, Arca, Linhoff etc) and having it all machined, shimmed, adjusted etc. to get everything to align perfectly.

And John you are always welcome to visit the factory in Israel, you know that
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zzzone
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« Reply #10 on: January 17, 2007, 04:03:03 AM »
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Thanks guys.

My negative comments relate to the Horseman SWD2 and the Rodenstock lens I waited for many weeks to be ordered from Japan

I recieved my replacement Cambo WDS last night and preliminary checks this morning with the Cambo/mamiya adapter show the Scheider lens to be close to perfect wide open.

Wrongly I was pleasantly surprised because there are a few things that interface and join together between the lens and the CCD on the Cambo.  I was thinking whilst putting it all together that maybe that was why the Alpa XY so cumbersome and expensive, tolerances etc etc!!

I still have the Horseman SWD2 and the Rodenstock lens.  If that set up was OK comparisons would be useful but I don't think any findings I might reveal would be very representative.

Thanks Yair for your recommendation Cambo/ Mamiya solution and to Teamwork/Phase in London for sorting all very quickly.  Credit where credit is due.

Regards Steve
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