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Author Topic: Focus Problems with Alpa 12SWA and Digitars  (Read 4825 times)
ericstaud
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« on: June 04, 2006, 03:31:56 PM »
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Has any one had trouble focusing with Helical focus mounted digitars?  I am using the 24, 35, and 60mm Digitars on my Alpa 12 SWA.  I have followed the instructions for shimming the adapter for my H1 mount Aptus 22.  I can find a shim combo that works for each lens, but each lens needs a different shim ammount than the others.  Do the lenses need to be returned?  Does Schneider or Alpa make shims that go into the lens mounts themselves?

Thanks,

Eric
« Last Edit: June 04, 2006, 03:32:20 PM by ericstaud » Logged
ynp
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« Reply #1 on: June 04, 2006, 04:39:25 PM »
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Has any one had trouble focusing with Helical focus mounted digitars?  I am using the 24, 35, and 60mm Digitars on my Alpa 12 SWA.  I have followed the instructions for shimming the adapter for my H1 mount Aptus 22.  I can find a shim combo that works for each lens, but each lens needs a different shim ammount than the others.  Do the lenses need to be returned?  Does Schneider or Alpa make shims that go into the lens mounts themselves?

Thanks,

Eric
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I had the same problem when I did my own shimming on my ALPA. I started with my helvetar, everything was OK, fitted the Digitar 35mm and everything was out of focus. Then I noticed that the rear element  on the 35mm was a little unsrewed. It did not effect  focusing problems when I was using the same Digitar on film (testing the lens before my Eyelike arrived). I tighten the lens and now check them before shooting.Hope that will help.
Yevgeny
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ericstaud
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« Reply #2 on: June 04, 2006, 11:32:11 PM »
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Thanks Yevgeny.

Would you say that your two lenses match excactly now?  Do the markings on your lenses match the distances to the subjects?

-Eric
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pixjohn
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« Reply #3 on: June 05, 2006, 12:46:43 AM »
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I don't have an Alpha but I have a few Schneider lens: 24xl, 35xl and 47xl on a Cambo Wide DS. I have no problems focusing any of my lenses. I also use live video to check focus. Since you have the Aptus 22 can you shoot tethered and use live video?

I also see you cross posed on RG site. Thats a dead waste of space now.
« Last Edit: June 05, 2006, 12:56:24 AM by pixjohn » Logged
ericstaud
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« Reply #4 on: June 05, 2006, 01:17:36 AM »
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Thanks for the reply John.  I don't have the live video dongle.  I don't mind checking focus on the A22 back or the computer for most of my work, which is fairly formal architecture.  When I got my camera about a week ago we were on our way out of town.  I shot several roadside landscapes and was very suprised returning home to find all three lenses had a different idea of what infinity was.  The usefullness of the camera will be more limited if I can't trust the markings on the lenses ( or if I need to bring a spreadsheet to interpret them).

-Eric
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DominiqueMarcWehrli
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« Reply #5 on: June 05, 2006, 04:25:47 AM »
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Dear Eric

Infinity position can be adjusted with the 3 screws marked with * on the attached information sheet. These informations are for the official Schneider helicoid mounts.

Regards
Dominique
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ynp
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« Reply #6 on: June 05, 2006, 07:04:39 AM »
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Eric,
 <<Would you say that your two lenses match excactly now? >>  
I have no problems with focusing  and both lenses match perfectly. I tried  my ALPA with 24mm at a dealer, and the files were sharp. Then I tried my  Eyelike back with ALPA TC and had no focusing problems with the combo.
<<Do the markings on your lenses match the distances to the subjects?>>
 Yes.I usually guess the distance for landscape but sometimes I have to be more precise with focusing and use a measure tape. Two weeks ago  I shoot a painting mounted on a wall in a small apartment  with my ALPA and started with the Helvetar. I used a measure tape to calculate the distance and dialed the distance on the lens. The painting filled the frame to the borders and I decided not to risk with the Helvetar which is a bit soft on the corners with digital. I put my 35mm on and used the same marking on the Digitar as I used on Helvetar. I did not move the tripod and did not refocus. Files were sharp. So I believe that once adjusted the camera/back combo behave she same with all lenses and on all ALPA bodies.
Yevgeny
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ericstaud
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« Reply #7 on: June 05, 2006, 10:57:59 AM »
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Infinity position can be adjusted with the 3 screws marked with * on the attached information sheet. These informations are for the official Schneider helicoid mounts.
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Thanks Dominique,
How is this done?  I assume you focus the lens so that infinity is sharp, then unscrew the three * screws and set the ring with the infinity mark at top?  Is that correct?  Or when you undo the screws does the front element fall off and a dozen miniature springs go shooting across the room?java script:emoticon('Shocked')

I think I will exaust the Dealer/Alpa route before I take a screwdriver to the lenses.
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ericstaud
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« Reply #8 on: June 05, 2006, 11:03:50 AM »
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Eric,
 <<Would you say that your two lenses match excactly now? >> 
I have no problems with focusing  and both lenses match perfectly.
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Thanks for this.  I was hoping for that answer.  I am waiting to hear from the dealer and Alpa on the matter.  Hopefully they will have an easy solution for me.

-Eric
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Fred Schang
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« Reply #9 on: June 07, 2006, 05:37:40 AM »
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I had my Aptus 22 shimmed at the dealer and I have experienced no difference in focusing between my 3 Schneider lenses, the 24, 35 and 90mm digitars.

I use a Leica Disto A3 in the field (whenever possible) for critical focus and I find it to be very accurate when shooting at closer distances than infinity.

Fred
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mkravit
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« Reply #10 on: September 10, 2006, 02:44:42 PM »
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I had my Aptus 22 shimmed at the dealer and I have experienced no difference in focusing between my 3 Schneider lenses, the 24, 35 and 90mm digitars.

I use a Leica Disto A3 in the field (whenever possible) for critical focus and I find it to be very accurate when shooting at closer distances than infinity.

Fred
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Great idea.
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ericstaud
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« Reply #11 on: September 10, 2006, 04:08:43 PM »
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In the end, returning my 35mm digitar is all that needed to happen.  Schneider told my that the markings on the focus barrels are only approximate (Here is LA, every lens for the movie industry has custom engraved focus markings because every lens sample is slightly different).  In the end, you just need to double check that the infinity setting for all the lenses work with the same ammount of shimming on your digital back adapter.

-Eric
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