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  1. #1
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    Buy or Trade - 400mm 8x10 in Shutter

    I am currently shooting my Cambo 8x10 with a 240mm lens. Love it for landscape work but would like a slightly longer lens for head and shoulders portrait work. All my 8x10 work is in B&W so coatings are not critical but would like wider aperture settings to help improve shutter speeds.

    Am retired on low, fixed income so price is important. Have Fuji GL690 in decent shape that I could trade for the right lens. Also would consider trading some nice Pentax 645 lenses.

    Feel free to PM with questions or options.

    Thanks

  2. #2
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    Convert

    Thanks. That is a great idea if I can make it work. I do have a Schneider-Kreuznack Symmar 150 on my 4x5 that can convert but it won't cover the 8x10 circle. The only lens I own that will cover the 8x10 is my Caltar-S II 240mm. I don't think it is convertible.

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    Ok, obviously it is time to do some research. Thanks.

    One small question. I have read about apertures being the diameter of the opening in comparison to the focal length but if I am going to calculate my own scale I may need some additional guidance. The way I understand this f16 on my Caltar is actually written as 240/16 mathematically. What I am not so sure of is how to calculate focal length once I figure out how to convert the Caltar from 240mm. Can you, or someone else, give me a little guidance on how to do this?

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    Focal Length

    Ok, this is what happened. When I focused on an object at infinity with the 240mm I measured 9.5 inches from the ground glass to the shutter. This agreed nicely with the lens specs. With the front part of the lens removed to convert to a longer focal length (which I assumed to be the correct method for doing this) I measured 13.5 inches from the ground glass to the shutter after focusing on the same image. This came out to 340 mm (give or take a millimeter or two.)

    However, the image I see in the ground glass is VERY soft and it took a lot of back and forth to feel confident I had actually focused properly. I focused on a distant tree, maybe 1/4 mile away, and with the 240 on the camera I could distinguish the leaves fluttering in the wind when I used my 8x loupe. With the lens converted to the longer focal length I could not distinguish those same leaves with the loupe. It was just a larger green mass which I knew to be leaves. I could distinguish the individual branches, but not the leaves. I am not sure that this will work out all that well for portraits.

    My grandkids just arrived so I am going to try focusing on them at close portrait distances to see if this image improves at all at the much closer distances involved in a head and shoulders portrait. I'll let you know how it turns out.

  5. #5
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    Quote Originally Posted by johnielvis View Post
    oh well...even if it don't work , at least you learn, right?
    That is where the fun is! That and those few terrific photos you are privileged to make in life.

    Thank you very much for your help. I'll stop it down and try some portraits with it today if I can get my grandkids to sit still long enough. The len has flash sync so I'll try it with a couple of strobes.



 

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