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Thread: Testing Lenses; Telescope Method

  1. #1
    Bart B's Avatar
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    Testing Lenses; Telescope Method

    Mounted a 15mm eyepiece lens from a spotting scope in a sheet of plywood fit to the back of my Super Speed Graphic. Racked the Graflex 1000 135mm Optar/Rodenstock lens out to get a sharp image in the eyepiece. The image was a 9X magnification. Pretty good image sharpness in the aerial image at the 135's focal plane with the lens wide open at f/4.5. Stopping down to f/16 through f/32 darkened the image but really sharpened it up to where I could see twice as many tree branches some 200 yards away.

    Replaced the Graflex 1000 lens with a Graflex 90mm Optar f/6.8 W.A. I'm thinking about buying. It's image was 6X magnification. Again, wide open, it was nothing to shout about. Stopping it down to f/16 through f/32 showed it to be a little sharper than the 135.

    The 90's Wollensak shutter's frozen but probably fixable. I may remove the front and back lens groups then put it in my ultrasonic cleaner with naptha to see if that helps. It's shutter speed dial is stiff and sluggish but the preview arm opens up and releases the shutter without problems.

    Anybody ever tested lenses this way? Without the shutter working, I thought this would be a decent test as the telescope eyepiece is designed to focus sharpest at an aerial image at its focal length. Its 15mm focal length makes it a 16.7X loupe and the aerial image is clean, not grainy like ground glass images are.

  2. #2

    Re: Testing Lenses; Telescope Method

    "Anybody ever tested lenses this way?"

    Yes, with 6, 12.5 and 25mm eyepieces, a few problems:

    it's only checking the very center of the image but will show the actual focus shift of the lens.

    you'll find there is almost no actual DOF, it's all an optical illusion.

    contrast and definition increase with ALL lenses by f/11, don't know if it's the lenses OR human vision thanks to the brightness, will need to try ND filters to find out.

    you will find ALL lenses are sharper than film can record, can NEVER blame the lens again.

    "Stopping down to f/16 through f/32 darkened the image but really sharpened it up to where I could see twice as many tree branches some 200 yards away. "

    at that distance you should see the veins in the leaves, pollen on the buds with a long enough lens. You will also see how LONG the camera shakes after just being touched and how COARSE the focus gears are.

    you can see the natural contrast and color saturation of each lens and compare them to each other. Surprising what lanthium glass does for color saturation.

    Interesting exercise but it's more fun to take pictures.

  3. #3
    Bart B's Avatar
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    Re: Testing Lenses; Telescope Method

    Quote Originally Posted by Paul Fitzgerald View Post
    it's only checking the very center of the image but will show the actual focus shift of the lens.
    I agree when the eyepiece is centered in the 4x5" frame. Moving it to the edge shows that old lens is decent enough, especially stopped down to f/22 and f/32. It appears to go down to almost f/45 with the aperture lever at its stop.

    I was somewhat hesitant about this lens as its serial number is G4xxxxN; probably an older one. Most I've seen have 6-digit serial numbers. But it's a coated lens in pristine condition. I just need to get its shutter unlocked; probably sonic clean it with a plastic-safe degreaser that dries residue free. Then have it lubed and test it for accuracy.

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    Re: Testing Lenses; Telescope Method

    If you simply want to compare two lenses to decide which one not not to use, nearly any testing method will do. But if you want to determine whether a lens is good enough to use (the winner of a two-way comparison may not be) there's no substitute for close examination of the image it puts on film. The image on film, not a scan.

    Which of your lenses' serial number begins with "G"? The Rodenstock Optar or the Wolly Raptar? I ask because Wollensak serial numbers were all numeric from the beginning of time until sometime in the late '50s or early '60s when they switched to alphabetic prefixes. I have Wollies whose serial numbers begin with D and E. G, if on a Wolly lens, would be quite late.

    The Optar badged Wolly lenses I have all have normal all-numeric Wollensak serial numbers. I don't know whether Graflex had Rodenstock assign anomalous (as R'stock serial numbers go) serial numbers to Optar badged Rodenstock lenses.

  5. #5
    Bart B's Avatar
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    Re: Testing Lenses; Telescope Method

    Quote Originally Posted by Dan Fromm View Post
    Which of your lenses' serial number begins with "G"? The Rodenstock Optar or the Wolly Raptar? I ask because Wollensak serial numbers were all numeric from the beginning of time until sometime in the late '50s or early '60s when they switched to alphabetic prefixes. I have Wollies whose serial numbers begin with D and E. G, if on a Wolly lens, would be quite late.
    It's a Wolly version with Full Synchromatic shutter. On the front lens mount:

    "3 1/2" (90mm) GRAFLEX OPTAR W.A. f/6.8 No. G44xxxN."

    The black round name plate has "Made by Wollensak for GRAFLEX,. INC"

    So maybe it's a late version.

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    Bart B's Avatar
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    Re: Testing Lenses; Telescope Method

    Quote Originally Posted by Bart B View Post
    It's a Wolly version with Full Synchromatic shutter.
    I think I'm confused on who made the glass for this lens.

    Here's the shutter's nameplate info:
    GRAPHEX
    FULL SYNCHROMATIC Made By WOLLENSAK For GRAFLEX INC.


    Here's the front lens group's nameplate info:
    3 1/2" (90MM) GRAFLEX OPTAR W.A. f/6.8 No. G44xxxN

    I think Wollensak made the shutter for Graflex. Who made the lens? It appears to be coated; white cloudy sky through a square window reflect three squares in the front element, 1 colored white, 1 pink and 1 blue.

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    Bart B's Avatar
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    Re: Testing Lenses; Telescope Method

    Here's a picture of an identical lens. Only the serial number on mine's G44xxxN.


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