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Replace 135mm lens - effect on range finder
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Tim Povlick



Joined: 12 Jun 2011
Posts: 36
Location: San Diego

PostPosted: Tue Jun 28, 2011 4:16 am    Post subject: Replace 135mm lens - effect on range finder Reply with quote

I am curious is one replaces a 'stock' 135mm lens with a Nikkor-W f/5.6 will the range finder still be accurate? Would it be trivial to adjust if not so? Hopefully not a cam swap. I have read the service manuals and they state the adjustments will vary with each lens, but...

Thanks,

Tim
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BrianShaw



Joined: 24 Dec 2006
Posts: 65
Location: Los Angeles, CA

PostPosted: Tue Jun 28, 2011 3:21 pm    Post subject: Reply with quote

You'll have to check the rangefinder against hte ground glass to know for sure. It will likely be quite close, but remember that the marked focal length of a lens is nominal not necessarily exact. With enough DOF you might not have to do anything. That was my experience swapping an Optar with a 1980's era Schneider lens. Adjusting the rangefinder is rather easy and it sounds like you already have the manual tha explains how to do it.
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Tim Povlick



Joined: 12 Jun 2011
Posts: 36
Location: San Diego

PostPosted: Wed Jun 29, 2011 3:56 am    Post subject: Reply with quote

Hi Brian,

Thanks for stepping up with the good information. I'll do as you suggest and check it against the GG. If the RF is a problem, a local (So. CA) camera store has an older gentleman that knows all about these cameras.

Thanks,

Tim
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45PSS



Joined: 28 Sep 2001
Posts: 3212
Location: Mid Peninsula, Ca.

PostPosted: Wed Jun 29, 2011 5:45 am    Post subject: Reply with quote

http://graflex.org/speed-graphic/top-rangefinder-cams.html
5 cams (or is it 6?) correspond to the "135mm" lens.
Graflex optically measured each lens then chose the closest cam or cut a new one if none were acceptabally close.
Start by trying the new lens at the infinity setting for the old then at 100 ft., 25 ft., 15 ft., and 10 ft. The greater the difference in actual vs marked focal lenght the greater the difference at closer distances.
http://graflex.org/articles/oakes/
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BrianShaw



Joined: 24 Dec 2006
Posts: 65
Location: Los Angeles, CA

PostPosted: Wed Jun 29, 2011 1:48 pm    Post subject: Reply with quote

I don't know who you are calling "an older gentleman", but the person I trust locally in So Cal is Steve Choi at Steve's Camera Repair in culver City. He's a bonifide Graflex expert... as well as bonifide Hasselblad expert... and probably anything else that is photographic.
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Tim Povlick



Joined: 12 Jun 2011
Posts: 36
Location: San Diego

PostPosted: Thu Jun 30, 2011 2:40 am    Post subject: Reply with quote

Thanks for the links to the info on the cams. Many different cams for similar 135mm lens. The odds of simple success diminish. It's pretty amazing one can claim it can focus at 100ft. I would like to have the RF work properly so the camera could be used as a "point N shoot".

Brian,

The camera repair guy I was thinking of is not the one you mention. Thanks for the great tip though.

Thanks!

Tim
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45PSS



Joined: 28 Sep 2001
Posts: 3212
Location: Mid Peninsula, Ca.

PostPosted: Thu Jun 30, 2011 2:47 am    Post subject: Reply with quote

And if I had my hands on a Crown with a factory matched lens/cam I would do the measurements and write up a procedure for making an accurate cam from scratch without any guess work.
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Tim Povlick



Joined: 12 Jun 2011
Posts: 36
Location: San Diego

PostPosted: Thu Jun 30, 2011 2:00 pm    Post subject: Reply with quote

You jogged my brain into gear, I actually have two identical Crown Specials using 135mm lenses. I can swap lenses and check the effects.

It should be possible to "image" the cams and then scan the image to get an accurate diagram of the cam. The cam surface one would bring into a spreadsheet and from there start the process of calculating cam surface profiles versus the lens.

To image the cam one could trace the outline on paper, or maybe make a contact negative. Comments?

The lens information required is accurate focal length and aperture, I believe.

Is that all the input required to solve the cam problem?

_ .. --
Tim
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45PSS



Joined: 28 Sep 2001
Posts: 3212
Location: Mid Peninsula, Ca.

PostPosted: Thu Jun 30, 2011 8:10 pm    Post subject: Reply with quote

http://www.southbristolviews.com/pics/Graphic/manual-pdf/TRFService.pdf
for reference.

1. With the bed fully retracted move the bed forward until the limit of the rangefinder travel is reached. Measure this distance, bed travel.
2. With the bed at infinity move it forward until the travel limit of the cam is reached. Measure this movement, cam travel.
3. Calculate the ratio of bed to cam movement.
4. Put the camera with matched cam and lens on a tripod and level the camera.
4a. Set up a test target such as multiple copies of the 1951 Air Force test target http://www.darkroomagic.com/DarkroomMagic/Camera.html on a board at camera height/level.
4b. set camera at infinity focus and lock the bed, remove camera from the tripod, mark infinity on the cam using a straight edge and machinist scribe where the follower arm touches the cam.
4c. set target 100 feet from camera film plane with camera remounted on the tripod, focus lens on the ground glass on the target, check RF for correct focus. Lock bed and scribe cam as in 4b.
4d. repeat 4b & 4c for 50 feet, 25 feet, 15 feet, 10 feet, 6 feet, 4 feet or the closest the RF travel limit will allow.

5. Measure and record the cam height at each scribed distance point, be sure to measure to the cam base when it is installed in the camera not the notched area. Record for future use, these heights will be constant for all cams/lens.

6. Install uncamed lens on the camera and critically focus on infinity and lock the bed.

Set up test target as in 4a. 100 feet from the camera film plane. Focus the lens on the test target then measure and record the distance the bed moved from infinity to 100 foot focus. Do the same for at least 3 other distances or all the distances.

Multiply the bed movement measurement by the cam travel ratio and record.

Cut a blank the same shape, length-side angles, as an original with the left edge at the manual stated infinity height and the right edge higher than the closest focus distance height.

The cam position is referenced to the lower right corner of the cam. Scribe the blank with the proper distance heights at the correct movement points then machine the top edge of the cam and test with the lens/target.

Use a digital caliper to make all measurements on the camera/cam.
Focus with the lens at minimum aperture (wide open).
Target distance measurements are more critical as you focus closer to the target. An inch or two at 100 feet won't make much difference but an inch will at 6 feet. A Pacemaker Speed can be used as the test camera but the cam scribing will be more difficult.
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Tim Povlick



Joined: 12 Jun 2011
Posts: 36
Location: San Diego

PostPosted: Fri Jul 01, 2011 2:43 am    Post subject: Reply with quote

Thanks for the details 45PSS about the cam and the link to the manual.
I was able to do some quick checking and given two Crowns and a Schneider 135mm lens (the Special Lens). Using this lens on the Crown it came with, the RF and GG were in perfect sync. The lens on the other Crown and it was a bit off. The Nilkkor 135 at first looked to be a loosing battle but with a target at 3 feet, I moved out the infinity stops until GG and RF agreed. This required 0.413" more in the direction away from the GG. At 3 feet things were in sync. Measurements at various distances showed the GG and RF stayed in sync. Pretty amazing.

The only trick is to be able to trip the Copal #0 shutter with the side trigger. I guess M-flash mode is a non-starter with a Copal #0 shutter. Perhaps a solenoid would solve that.

Many thanks for your and everyone else s help with this thread.

Best Regards,

Tim
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45PSS



Joined: 28 Sep 2001
Posts: 3212
Location: Mid Peninsula, Ca.

PostPosted: Sat Jul 02, 2011 3:52 am    Post subject: Reply with quote

Looking at the cam list there are 2 cam numbers that are 1.5mm apart in measured focal lengths in the 135mm ballpark. Being you only moved your infinity stops .4mm says the lens is within .5mm of the focal length the cam was cut for so it stands to reason that the RF will be very close to accurate focus for the lens throughout the focusing range.

What are your cam numbers?
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Tim Povlick



Joined: 12 Jun 2011
Posts: 36
Location: San Diego

PostPosted: Mon Jul 04, 2011 1:47 pm    Post subject: Reply with quote

Sorry for late response...

I checked the instructions about pulling the cam and looked inside the camera to do this but am to intimidated to pull them. I'm afraid of breaking something that is working. Sorry...

Thanks for your help and information.

Tim
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1banjo



Joined: 16 Nov 2008
Posts: 478
Location: kansas

PostPosted: Mon Jul 04, 2011 6:10 pm    Post subject: Reply with quote

on a super graphic open the camera & put the bed in the droped posen.
put the camera in your lap top down with the back about a 45* away from you so the bellows is to you. don't pull out the bellows just leave it all the way back in. just so you can see past the end of the bed and see the cam cover. open it out to your right. Now you can see the cam push the cam from lift to right about a 1/4" then with one fanger pull{slide} out the lift corner of the cam
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45PSS



Joined: 28 Sep 2001
Posts: 3212
Location: Mid Peninsula, Ca.

PostPosted: Mon Jul 04, 2011 9:23 pm    Post subject: Reply with quote

There is nothing to break unless you force something. The Pacemaker series are harder to change cams in than the Super series as the Pacemaker cams are smaller.

The most common breakage is the plastic cap/plunger at the bed end of the actuator tube comes off and the balls and spacers pour out of the tube. There are 43 to 45 of each.
The second is the 50% transmission mirror looses its reflectiveness resulting in a weak or no RF image.
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Tim Povlick



Joined: 12 Jun 2011
Posts: 36
Location: San Diego

PostPosted: Tue Jul 05, 2011 1:15 am    Post subject: Reply with quote

This test was run on a Crown. Is pulling the cam "dangerous" / difficult?

Tim
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