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Problem with 11" lens

 
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Sirius Glass



Joined: 06 Jun 2010
Posts: 123
Location: Southern California & Virginia

PostPosted: Mon Jun 20, 2011 11:52 pm    Post subject: Problem with 11" lens Reply with quote

I just received a Dallmeyer Dallon 11" f/5.6 lens mounted on the 3 3/4" x 3 3/4" Graflex Model D lens board. When I try to focus on infinity the lens is not far enough back at the closest in position for the Model D. The mounting ring is attached to the front of the lens board. Does the lens board need to be counter bored or do I need to remount the mounting ring on the inside of the board?

Steve
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45PSS



Joined: 28 Sep 2001
Posts: 3201
Location: Mid Peninsula, Ca.

PostPosted: Tue Jun 21, 2011 5:53 am    Post subject: Reply with quote

Remove the lens from the board then measure from the back edge of the lens board to the lip of the mirror frame when it is at its closest point.

Next mount the lens in the board and measure how far it currently extends behind the lens board. Allow 1/64-1/32 inch clearance between the mirror frame lead edge and the lens rear element/barrel (whichever is longest) if you decide to put the mount flange on the rear or recess the board.

If there is not enough clearance between the mirror frame lead edge and rear of the lens when recessed then consider putting a shim under the view ground glass and the back frame to move the film plane to match the lens.

arc of mirror ) |rear of lens when mounted
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Sirius Glass



Joined: 06 Jun 2010
Posts: 123
Location: Southern California & Virginia

PostPosted: Tue Jun 21, 2011 4:29 pm    Post subject: Reply with quote

Thanks, I will measure it tonight.

The lens worked in a Model D that the seller's father used, so I am guessing that I would need to counter board [mill] between 1/16" to 1/8" off the front of the board and glue a 1/8" small board to the back for strength.

Once I get the measurement, I will need to find someone with a small milling machine that will do wood work.

Steve
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Sirius Glass



Joined: 06 Jun 2010
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Location: Southern California & Virginia

PostPosted: Wed Jun 22, 2011 12:50 am    Post subject: Reply with quote

After I moved the front out to make sure that I cleared the back of the lens, I attached the lens to my 1928 4"x5" Graflex Model D. At the most retracted point, infinity was not in focus. I figured that maybe I could remount the lens back further on the lens board a short distance.

Therefore I moved lens further out and raised the mirror. Then I moved the lens back in to check the clearance. When I slowly lowered the mirror, the mirror touched the top of the lens tube. So I cannot remount the lens and use it.

I tried it on my Pacemaker Speed Graphic. I have to move the front standard out to focus at infinity. To focus closer I have to move the standard forward and refocus. The Speed Graphic will not move back and forth enough to place the front standard at one place.


I am happy with the lens, but it will not work in my cameras. If you have no other ideas, I will return it.

Steve
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45PSS



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

PostPosted: Wed Jun 22, 2011 3:32 am    Post subject: Reply with quote

An 11 inch lens should focus infinity 11 inches from the film plane. A Speed Graphic has a 12 3/4 inch bellows so by setting the front standard at the forward edge of the rails then moving the rails out you should be able to focus the lens from infinity to 15 feet or so. I use a 10 inch Wollensak on my Super Speed (12 1/2 inch bellows) and it will focus to 10 feet easily and I tried a 12 inch lens on it and it would focus infinity to 25 feet.

I no longer have the reference books for the Graflex but I think the minimum focus distance is in the 7 to 9 inch range. I think you need to extend the lens out further to focus infinity on the Series D not move it in closer.

Wait a few days before returning the lens to give other knowledgeable members time to respond.
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Dan Fromm



Joined: 14 May 2001
Posts: 1881
Location: New Jersey

PostPosted: Wed Jun 22, 2011 8:12 am    Post subject: Reply with quote

Sirius Glass wrote:


I tried it on my Pacemaker Speed Graphic. I have to move the front standard out to focus at infinity. To focus closer I have to move the standard forward and refocus. The Speed Graphic will not move back and forth enough to place the front standard at one place.

Steve
Steve, its early in the morning and I haven't had my coffee yet. I don't understand what you mean, please explain.

The Dallon is a telephoto lens so its back focus is shorter than one would expect given its focal length. Teles also have smaller coverage than lenses of normal (neither telephoto nor retrofocus) construction. According to the VM an 11"/5.6 Dallon covers 3x4, 12" is needed for 4x5.
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Sirius Glass



Joined: 06 Jun 2010
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Location: Southern California & Virginia

PostPosted: Wed Jun 22, 2011 7:50 pm    Post subject: Reply with quote

1) If I pull the front standard of the Speed Graphic out to a point, A, and have the front standard full retracted I can focus from infinity to some point closer and the the focus knobs can go no closer.

2) To go closer, I retract the front standard and move from point A to a further out point B, which is where the front stardard stopped in step 1. Then I can move the focus via the focus knobs to a new limit.

It seems to take three or four placements of the front standard to cover the range.

Dan's comments on the 11" f/5.6 only covering 3x4, adds to my conculsion that I will not be happy in the long run with this lens.

The seller understood my problem and has argeed to take back the lens and refund the PayPal less the shipping costs.
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Dan Fromm



Joined: 14 May 2001
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PostPosted: Thu Jun 23, 2011 1:45 pm    Post subject: Reply with quote

Steve,

Thanks for explaining. What you've described is normal. A Graphic's focusing rack has limited travel so focusing closer than it will let you when the front standard is positioned so that the lens will focus a tiny bit through infinity with the rack all the way back requires repositioning the front standard.

You'll have the same "problem" with any long lens.

I've found what Fred Lustig calls a chinaman - a sort of sliding infinity stop, for a picture of one look here http://www.galerie-photo.com/telechargement/dan-fromm-6x9-lenses-v2-2011-03-29.pdf , see figures 27 and 28. A chinaman prevents unintentional swing.

Cheers,

Dan
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Sirius Glass



Joined: 06 Jun 2010
Posts: 123
Location: Southern California & Virginia

PostPosted: Thu Jun 23, 2011 5:16 pm    Post subject: Reply with quote

I have a 90mm and 135mm lenses for the 4"x5" Pacemaker Speed Graphic. I have a 190.5mm [7.5"] lens for the 4"x5" Graflex Model D. Tomorrow I should be receiving a 380mm [15"] lens for the Graflex.

My thoughts are that I would use the tilt, shift, and rise for the 90mm and the 135mm on the Speed; I would not use the tilt, shift, and rise for the 190.5mm lenses and longer.

Since I have the 190.5mm lens, I do not see a need for a 203mm or 210mm lens for the Speed.

So with:
90mm
135mm
190.5mm
380mm

I would like to get something in the 250mm to 300mm [10" to 12"] range for the Graflex.

Steve
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Dan Fromm



Joined: 14 May 2001
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PostPosted: Thu Jun 23, 2011 9:20 pm    Post subject: Reply with quote

Pardon my ignorance, but I don't know the 4x5 Super D's minimum and maximum extensions. I also don't know its lens throat's diameter.

So I have no idea which lenses it will focus with the lens mounted entirely in front of the board or which ones can be mounted through the board. But you have the camera, can measure, and can then look up back focus in tables of lenses' properties. Don't have to measure very precisely.
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