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Thread: How To Properly Determine Infinity For a Lens?

  1. #1

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    How To Properly Determine Infinity For a Lens?

    I want to make sure I fully understand how to determine infinity for all of my various large format lenses.

    I assume that I will need to know the flange focal distance for the lens and then from there, I really don't know how to use that information to determine infinity for each lens. I have both standard and telephoto lenses, so I am hopeful that someone here will teach me how to do this properly.

    Thanks in advance for teaching an old guy something new today.

    Larry

  2. #2

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    Re: How To Properly Determine Infinity For a Lens?


  3. #3

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    Re: How To Properly Determine Infinity For a Lens?

    You have properly cut cams, the infinity stops and focusing scales for your Technika?

  4. #4
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    Re: How To Properly Determine Infinity For a Lens?

    Not clear what you're asking. Are you trying to determine how far a target has to be for it to be a reasonable proxy for infinity when you are calibrating a rangefinder? If not, what exactly are you trying to understand?

  5. #5

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    Re: How To Properly Determine Infinity For a Lens?

    Hi Bob. Yes, I have a properly cut cam for my lens.

    I know the default answer is to send the camera to an authorized service center for setup and calibration, but I simply don't have months to wait, so I want to at least try and understand what is involved so I can make an educated attempt at trying to setup my lens on my Master Technika.

    I believe the first step is to set the lens at infinity and that is what I am asking the original question, but I want to make sure I know what that means so I start off with the lens in the right place on the rails.

    Any pointers are much appreciated.


    Quote Originally Posted by Bob Salomon View Post
    You have properly cut cams, the infinity stops and focusing scales for your Technika?

  6. #6
    Tin Can's Avatar
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    Re: How To Properly Determine Infinity For a Lens?

    If focusing on a billboard a mile distant and setting infinity there is not good enough, you are taking pictures of satellites, or moons

    It is not significant, meaning you will not see a difference

    Set infinity STOPS for something you shoot, like trees, mountains, moons
    sin eater

  7. #7

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    Re: How To Properly Determine Infinity For a Lens?

    Thank you.

    Quote Originally Posted by Tin Can View Post
    If focusing on a billboard a mile distant and setting infinity there is not good enough, you are taking pictures of satellites, or moons

    It is not significant, meaning you will not see a difference

    Set infinity STOPS for something you shoot, like trees, mountains, moons

  8. #8

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    Re: How To Properly Determine Infinity For a Lens?

    Quote Originally Posted by LFLarry View Post
    Hi Bob. Yes, I have a properly cut cam for my lens.

    I know the default answer is to send the camera to an authorized service center for setup and calibration, but I simply don't have months to wait, so I want to at least try and understand what is involved so I can make an educated attempt at trying to setup my lens on my Master Technika.

    I believe the first step is to set the lens at infinity and that is what I am asking the original question, but I want to make sure I know what that means so I start off with the lens in the right place on the rails.

    Any pointers are much appreciated.
    Presuming your cam has the same serial number as your lens you install the cam. Focus on something several hundred yards from you. Marflex used a telephone pole and wires across the street from our offices. Focus through the gg till the wires and pole are as sharp as possible. Then look through the rangefinder to see if it agrees with the gg.
    If yes, carefully install the infinity stops against the front standard, carefully because the screws that fasten the stops have sharp pointed screws that will dig into the chrome plated focus tracks. If the stops are moved those screws will leave small pit marks in the tracks that can not be removed.
    If no your cam is not cut for your lens.
    When one buys a new cammed lens from the factory or the distributor the lens box comes with the stops and the focusing scale for the bed. Along with these you also get a cardboard tube that contains a focusing target and instructions. These items let you properly install the infinity stops at the proper position on the tracks when viewed from about 5 meters on the gg.

    It isnít quite as simple as it would appear at first glance.

    Why would it take months to properly adjust your camera?

  9. #9
    Corran's Avatar
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    Re: How To Properly Determine Infinity For a Lens?

    If you have the Technika, cams, and lens, first get the lens on the camera and pull the front standard out to middle of the rail (if you have a wide-angle that needs to have the rail pushed back or a telephoto with it moved forward on the extension, set it as such).

    Next, focus in the rangefinder on a very clear target at close to infinity. For the purpose of infinity, anything farther than a couple hundred feet is fine, you aren't going to be able to discern anything past that in the RF. After that is set, lock the focus.

    Then, put the infinity stops on the camera and let them move freely on the rail with the tabs flipped up. Move the lens on the rail till it is in focus on the ground glass. Snug up the infinity stops and tighten them down slightly.

    Now focus on something about 25 feet away. Check and see if the RF and GG match up. If not, you may want to move the stops till it is, and focus on infinity second - choose whatever works best for your shooting style, but most likely they will both be in focus at all ranges unless you have something seriously wrong with the camera, lens, or cam. Once you are satisfied, you can tighten down the stops more tightly. They can move from the impact of the front standard if not tightened enough.

    You shouldn't need the factory to do this. I've done it, even with mismatched cams/lenses which often are "close enough" for most situations.
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  10. #10

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    Re: How To Properly Determine Infinity For a Lens?

    Hi Bob, I was able to get the cam and lens all setup and everything works perfectly. I even exposed a couple sheets of film to confirm. I am super happy about this!

    In regard to the couple of months comment, that is the time it would take to ship the camera, wait for it to be serviced and then return shipped. Now I don't have to wait for any of this!!

    Thanks again.




    Quote Originally Posted by Bob Salomon View Post
    Presuming your cam has the same serial number as your lens you install the cam. Focus on something several hundred yards from you. Marflex used a telephone pole and wires across the street from our offices. Focus through the gg till the wires and pole are as sharp as possible. Then look through the rangefinder to see if it agrees with the gg.
    If yes, carefully install the infinity stops against the front standard, carefully because the screws that fasten the stops have sharp pointed screws that will dig into the chrome plated focus tracks. If the stops are moved those screws will leave small pit marks in the tracks that can not be removed.
    If no your cam is not cut for your lens.
    When one buys a new cammed lens from the factory or the distributor the lens box comes with the stops and the focusing scale for the bed. Along with these you also get a cardboard tube that contains a focusing target and instructions. These items let you properly install the infinity stops at the proper position on the tracks when viewed from about 5 meters on the gg.

    It isn’t quite as simple as it would appear at first glance.

    Why would it take months to properly adjust your camera?

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