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Thread: Tessar (Ektar) construction

  1. #1

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    Tessar (Ektar) construction

    I removed the front cell from a 127mm Kodak Anastigmat Special (the 1944 military ektar) for cleaning, while the shutter happened to be open. The rear projected a very decent looking image of the room ceiling light fixture onto my work desk. What's the deal with that? Is a Tessar a cemented anastigmat pair in the rear? The front didn't project anything but light so it's obviously not a corrected dialyte pair?

    Thanks,
    Dan

  2. #2
    the Docter is in Arne Croell's Avatar
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    Re: Tessar (Ektar) construction

    Quote Originally Posted by Fotoguy20d View Post
    I removed the front cell from a 127mm Kodak Anastigmat Special (the 1944 military ektar) for cleaning, while the shutter happened to be open. The rear projected a very decent looking image of the room ceiling light fixture onto my work desk. What's the deal with that? Is a Tessar a cemented anastigmat pair in the rear? The front didn't project anything but light so it's obviously not a corrected dialyte pair?

    Thanks,
    Dan
    All the focusing power of a Tessar is in the cemented back group, the front cell pair actually has negative power and mainly corrects the aberrations of the back group. Thus the cemented back group does form an image, but it has a shorter focal length than the full objective, and is very badly corrected on its own - certainly not an anastigmat pair!

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