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This lens is the  APO-Telyt 280/4,
 one of the best ever made by any brand.

Thanks to a loan from a customer we can write the following instructions.
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It is a R-cam lens.
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First, remove the bayonet screws.
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Push the aperture lever until the bigger gap side.
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This way, it is possible to remove the bayonet and the black shroud all together.
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There is no need to disassemble the black shroud.

NEW!
With the new Leitax mount model, you can reuse the black tube to avoid flares, take a look here.
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The small bearing ball is in place.
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Put some grease into the hole with spring where the ball goes, and some more on the ball.
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Now we can install the new bayonet, the red dot close to the scale center.

First the four longer screws, and tight all the screws in a cross pattern, a bit one after another.
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All is black
inside except a couple of bright metal screws.
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So, I've painted them with the flat black marker I got from Micro-Tools.
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Also note this lens has lost the red plastic hemisphere.
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With a bit of glue the lens looks  better now.
Ready







Ready, now it is possible to use this lens on Pentax and Nikon-F cameras.

I would like to say thanks to our customer and friend James for the possibility to try the Leitax bayonet on this lens.
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