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Thread: f-Stops for Ilex 7.5" Paragon

  1. #1

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    f-Stops for Ilex 7.5" Paragon

    I have an Ilex Paragon Anastigmat 7.5" f4.5 in a No. 3 X Universal shutter. The lens came with a Meridian 4x5B that I purchased. The f-stops have been marked over (ugh). I'm not sure if this is the original shutter. Is there a way for me to calculate the f-stops?

    Bob K.

  2. #2
    Jim Jones's Avatar
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    Re: f-Stops for Ilex 7.5" Paragon

    Divide the f/number you want to mark on the shutter into the 7.5" focal length of your lens. This will give the apparent diameter of the aperture as seen through the front of the lens. Adjust the diaphragm until it appears to be that figure. For example, to mark f/4.5 on the shutter, the apparent diameter of the diaphragm should be 7.5/4.5 or 1 2/3 inches. For maximum accuracy, move your eye by that 1 2/3 inches as you move from checking one edge of the diaphragm to the other, so you are always looking directly into the front of the lens instead of looking at a slight angle.

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    IanG's Avatar
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    Re: f-Stops for Ilex 7.5" Paragon

    It does sound like the shutter aperture scale was originally calibrated for a different FL. An easier option would be to photograph the scale of a similar 7" Paragon, I think I have one somewhere in a cabinet here. I'll see what I can do later today or tomorrow.

    Ian

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    Re: f-Stops for Ilex 7.5" Paragon

    Quote Originally Posted by IanG View Post
    It does sound like the shutter aperture scale was originally calibrated for a different FL. An easier option would be to photograph the scale of a similar 7" Paragon, I think I have one somewhere in a cabinet here. I'll see what I can do later today or tomorrow.

    Ian

  5. #5

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    Re: f-Stops for Ilex 7.5" Paragon

    Well, you know that the lens wide open is f4.5, So you can aim the camera at an evenly lit wall (but camera is focused for infinity), and if you have a decent digital spotmeter, you can read exactly the same spot on the GG (under dark cloth) as you stop down, and if there is a tape label where the scale should be, every time you read an f stop lower, dab a mark with a pen... Then mark the f stop # next to that mark...

    This works quite well if you do it right to get a close (ballpark) f # yourself for the lens testing... (This is not for shooting, as different GG's have different brightness densities, but good enough to make a scale...

    If you love the lens, send it to SK Grimes for a new scale (not too much $$$)...

    Good luck!!!

    Steve K

  6. #6

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    Re: f-Stops for Ilex 7.5" Paragon

    Steve, that's just what I did. SK Grimes has a very reasonable price.

    Thanks.

  7. #7
    Serious Amateur Photographer pepeguitarra's Avatar
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    Re: f-Stops for Ilex 7.5" Paragon

    Quote Originally Posted by LabRat View Post
    Well, you know that the lens wide open is f4.5, So you can aim the camera at an evenly lit wall (but camera is focused for infinity), and if you have a decent digital spotmeter, you can read exactly the same spot on the GG (under dark cloth) as you stop down, and if there is a tape label where the scale should be, every time you read an f stop lower, dab a mark with a pen... Then mark the f stop # next to that mark...

    This works quite well if you do it right to get a close (ballpark) f # yourself for the lens testing... (This is not for shooting, as different GG's have different brightness densities, but good enough to make a scale...

    If you love the lens, send it to SK Grimes for a new scale (not too much $$$)...

    Good luck!!!

    Steve K
    Reviewing lesson from the past. Great forum, great way to learn.
    "I have never in my life made music for money or fame. God walks out of the room when you are thinking about money." -- Quincy Jones

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