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Thread: Summarit 5cm F1.5 modified for close-up/wide-open focus

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    Summarit 5cm F1.5 modified for close-up/wide-open focus

    The Summarit has an interesting design compromise to deal with focus shift. Focus shift occurs as a lens is stopped down, due to spherical aberration. Focus shift basically shifts the actual focus of the lens towards infinity as the lens is stopped down, toward the image plane as the lens is opened up.

    The Summarit is a 51.1mm focal length lens, shorter than the Leica 51.6mm standard. The optics move 1:1 with the RF cam, an indexed cam is not used to correct the error. The lens is factory set for infinity to be in proper focus at F1.5. Close focus is acheived at F2.8, the focus shift pushes the lens in agreement with the RF. At F1.5, the 51.1mm lens front-focuses because the actual focal length is shorter than what the RF is calibrated for. Clear as mud? Me. to, so I changed the actual focal length of the lens to agree with the RF.

    The actual focal length of a complex lens can be set by adjusting the spacing between the groups. Basically, think of it as a zoom lens. The rear groups are held in by a single retaining ring. The fit is tight, and the front section needs to be unscrewed to push them through. Be careful of the aperture blades- open them fully, be careful to keep them in place. If anyone wants to try this, I'll photograph this up.

    The Shim from a Jupiter-8 fits perfectly around the glass of the rear group. I used a 0.2mm shim, do not think I could hit it better. SO: Rear groups moved out 0.2mm, lens re-assembled, focus is quite good at F1.5 from close-up to infinity.





    Infinity at F1.5,





    Bokeh looks good, F1.5.



    fence Slats and brick Walls are good for testing the corner-to-corner performance of the reassembled lens.
    If an element is out of alignment or in backwards, this usually gives a clue.
    F1.5



    Summarit Swirlies are still swirling.





    I am looking forward to trying this lens on the M9 Monochrome. The Summarit is great at taming highlights and preserving shadow.

    The modified lens back-focuses when stopped down, but at least is consistent at all distances.
    Last edited by Brian S; 6th July 2012 at 19:59.
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    Re: Summarit 5cm F1.5 modified for close-up/wide-open focus

    so now it's good at all distance for f/1.5, is it as good when stopped down?

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    Re: Summarit 5cm F1.5 modified for close-up/wide-open focus

    Summarit, F4, on the Leica M9:



    100% crop:



    Focus, backed off slightly just like with a Sonnar optimized for F1.5. Otherwise actual focus would be about 1" behind the RF.

    The Summarit and Summilux V1 use the same optical formula, 7 elements in 5 groups (1-2-2-1-1). Now I'm wondering if the biggest change to the Summilux was making it a 51.6mm lens.

    This lens is on the M9, and I will be shooting with it. I have a second Summarit- will probably leave it alone for now.

    In the 1970s, Jason Schneider listed the Summarit as a lens that was as good as lenses current at that time. That seems to go against it's reputation at-large. My sample has now been cleaned and optimized for wide-open use. It really does improve the wide-open performance. That has been my one issue with it- soft used wide-open. Until now.

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    Re: Summarit 5cm F1.5 modified for close-up/wide-open focus

    Step by Step images posted in the projects section on serious compacts.

    Summarit 5cm F1.5: modify for using F1.5 at all distances

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    Senior Member dude163's Avatar
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    Re: Summarit 5cm F1.5 modified for close-up/wide-open focus

    cool!

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    Re: Summarit 5cm F1.5 modified for close-up/wide-open focus

    I first read about the summarit being optimized for mid-distance/stopped-down images and the Nikkor being optimized for close-up/wide-open work on Dante Stella's site several years ago.

    Dante Stella

    On the digital camera, was easy to see the Summarits were optimized for F2.8 close-up, and after discovering the actual focal lengh was 51.1mm- all of a sudden the statement on Dante's site made sense.

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    Re: Summarit 5cm F1.5 modified for close-up/wide-open focus

    Nice mod, Brian! I wonder if there's something similar going on with the Canon LTM 50/1.5, which I've heard is also optimized for f/2.8?
    ::Ari
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    Re: Summarit 5cm F1.5 modified for close-up/wide-open focus

    The Canon 50/1.5: It is optimized for F2.8 in my experience with three of them. I'm probably the person that posted this on RFF years ago. I changed the shim on mine to optimize for F1.5. It is quite good, closer in rendition to the Zeiss Sonnar.

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