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Thread: Inputs on my newly acquired 35mm lux re: focus shift

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    Inputs on my newly acquired 35mm lux re: focus shift

    Testing a newly acquired Summilux ASPH after selling all my other lens. Not as good as the deal right now on the for sale forum. I don't even know if I am doing this right so forgive me. This is paired with the M8.

    f1.4

    f1.4

    f1.4

    f2.0

    f2.8

    f4.0

    f5.6

    f8.0
    Last edited by blimey; 13th April 2012 at 10:53.

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    You know, when I tested my ZM50 C-Sonnar for focus shift, I spread out a piece of paper with lots of text (like newspaper). Then I focused a marker at the MFD at the widest aperture. Once set, I simply take shots as I turn the aperture ring. Reading the lines of text that was focused, I could tell there was about an inch of back-focus at f/1.5 and determined my lens was optimized for f/2.8.

    In your case though, even if there was focus shift, I don't think it's as bad as the ZM Sonnar.
    David Young
    My journey into Leica: LeicaLux.com

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    Use a ruler or something that gives an idea of where the actual focus falls.

    I use a Fence Post.


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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    ok. ill do that

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    Yes, a round ball isn't exactly a good object to test for focus shift..
    Scott

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    You might also want to focus bracket your wide open shot over say, three or four frames. Just to make sure it's not just a slight misfocus on your part.

    Pay attention especially if you just stop down from there - because if wide open is off, all the rest will be also (just hidden by DoF for the most part).

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    see above. ok i saw a few post about using battery(focus on the word PHILIPS) so i tried it. i can't find a ruler right now. shot at 0.7m(mfd). something is off at f1.4.

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    Oh, duh! Missed that. :sleep006:

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    Quote Originally Posted by Double Negative View Post
    Oh, duh! Missed that. :sleep006:
    no.. i just updated the original post to clean up the post. =)

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    Quote Originally Posted by blimey View Post
    no.. i just updated the original post to clean up the post. =)
    Aha!

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    The batteries need to be placed at different distances . The you focus on the middle battery . This allows you to see where the actual focus point is and how it changes . A good reference is to look at the battery just in front and just behind the target ...do they both look about the same when you focus. This helps minimize focus error.

    The 35 1.4 asph has a well known focus shift as you stop down. If the lens is set to be perfect at 1.4 you will have sufficient back focus at f2.8/f4 to exceed your DOF . At f5.6 the DOF catches up but the bias is still back . The optimum focus calibration is to make f2 perfect and allow f1.4 a small front focus ..this is just enough to bring f2.8/f4/f5.6 inside the DOF . You can easily learn to adapt to a minor FF at 1.4 and you probably miss by this much if shooting hand held anyway .

    This is a characteristic of the 35 1.4 asph that was corrected by the floating elements in the current version (FLE). Many photographers have worked around this issue and once the camera /lens are calibrated you can make the small adjustments to be consistent .

    When testing you should take 3-6 shots to eliminate your own focus errors .

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    Agree with above. Lens is good as long as you know how to compensate for the deficiencies in the optical design.
    Personally, I didn't like the focus shift. I had to intentionally force the rangefinder patch go past the point of overlap, and it threw me off when I switched lenses.
    Scott

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    A couple of easy to find objects to do focus testing:
    1. tape a piece of newspaper of the wall and shoot at it at 45 degrees. The classified page is best for this purpose. Mark the point you are trying to focus, shoot several shots as others have suggested to eliminate focusing error on your part, refocus every time. Use a sturdy tripod, and shutter release cable if available.
    2. Lay a measuring tape on the floor and do the same, 45 degree angle, several shots, refocus, tripod and shutter release cable.
    Oh yes, aperture wide open.
    Phil

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    I do not think (based on the ball/battery photos) there is anything wrong with your lens. You need better light.

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    thanks for the input everyone.
    i'll try again.. but still love the rendering when it's spot on.

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    Re: Inputs on my newly acquired 35mm lux re: focus shift

    The lens is a touch softer at f1.4 anyway, so it is a matter of guessing how much that is involved or if it is focus shift. But from your battery test I don't think you will have so much focus shift in real life photography to make much difference, unless you specialise in photographing batteries.....

    There is no big jump in focus in your pictures, that is when focus shift can be a big pain when shooting close to medium distance, so if it is off a tiny fraction from where you focused it won't be noticable or be covered by DOF most of the time. I had an otherwise lovely CV 28mm Ultron that was like a bucking bronco with its focus shift at all the sweet to use mid-apertures, so it had to go.

    Steve

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