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Thread: Front Focusing Summilux 75

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    Front Focusing Summilux 75

    My Lux 75 focuses fine at close distance, but front focuses when with distant subjects.

    Can this be easily corrected?

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    Re: Front Focusing Summilux 75

    The lens is not front focusing. Either there is a problem with the rangefinder system or the lens cam. The rangefinder can be calibrated easily, but if all your other lenses are fine, then that will not solve your problem. If the repair guy wants both the lens and camera, then they are going to calibrate the camera to the lens, not want you want. The other is getting the lens calibrated which is much harder.

    But I really don't understand the problem. Generally if the rangefinder or lens is not calibrated, then it is out for the entire focus range. It is odd that it is not focusing accurately at longer object distances even when DoF is increasing. I would call Leica and ask them.

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    Re: Front Focusing Summilux 75

    I have no problem with other lenses that I'm using...
    24/2.8 ASPH or Cron 35 ASPH, and even zeiss lens focuses correctly....

    The lens seems to front focus only when I take pictures that are more than 5-6 feet away.

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    Re: Front Focusing Summilux 75

    Quote Originally Posted by Shashin View Post
    It is odd that it is not focusing accurately at longer object distances even when DoF is increasing. I would call Leica and ask them.
    I can relay my quite extensive experience with a aquantences 90mm f2 Cron (E55), the last version prior to the AA on both a perfectly calibrated M8.2 and M9. His lens would focus perfectly from min. distance to mid-range. At longer distances to infinity, his lens would quite evidently front focus. It didn't matter what apertures were selected. He had two very well qualified and techs on seperate occasions have a go at adjustment and although they somewhat improved upon the front focusing at long subject distances, it could never be fully fixed and simply remained as his only lens that exhibited this trait. I tested this particular lens pre and post adjustment. The lens was barely used from being brand new. No real difinitive explanation was given as to the cause of this front focusing, and it appeared both techs were stumped as to why...although they mentioned it wasn't the first time they encountered this in a lens.

    Dave (D&A)

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    Re: Front Focusing Summilux 75

    Now I'm in a state of panic......
    especially if this can't be corrected.......

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    Re: Front Focusing Summilux 75

    I'm sure you've done your diligence but when I had this lens, I remember having some difficulties in focusing due to shallow DOF. For me, there was definitely a learning curve. But I also remember that the lens had some slight focus shift through the distance range.
    It is one of those lenses where you learn how to use over time. I think this is one of those lenses where it's worth the investment to take the time and learn.
    Scott

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    Re: Front Focusing Summilux 75

    I sent my 75 Summilux to DAG to get the focusing all aligned and now works fine with the M9. I would suggest giving him a call to discuss.

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    Re: Front Focusing Summilux 75

    It could be that the actual Focal Length of this particular lens is slightly too short. That is the only reason that I can think of to explain why a lens focuses at infinity but shows front-focus at close distances when used on a camera that is perfect with other lenses. I've had this problem on a couple of lenses. On the Summarit 5cm F1.5- Stopping down to F2.8 solves the problem with front-focusing at 1m, using at F1.5 the lens is perfect at infinity. Taking the optics out of the focus mount, the actual focal length scribed on the mount is 51.1mm. A second lens with the same issue: problem solved by moving the rear optics out slightly, which increases the acual focal length. "It just Works".

    http://www.seriouscompacts.com/f96/1...-jupiter-8364/

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    Re: Front Focusing Summilux 75

    Quote Originally Posted by Brian S View Post
    It could be that the actual Focal Length of this particular lens is slightly too short. That is the only reason that I can think of to explain why a lens focuses at infinity but shows front-focus at close distances when used on a camera that is perfect with other lenses. I've had this problem on a couple of lenses. On the Summarit 5cm F1.5- Stopping down to F2.8 solves the problem with front-focusing at 1m, using at F1.5 the lens is perfect at infinity. Taking the optics out of the focus mount, the actual focal length scribed on the mount is 51.1mm. A second lens with the same issue: problem solved by moving the rear optics out slightly, which increases the acual focal length. "It just Works".

    1950 KMZ J-3: first infocus images from a very early Jupiter.
    I think his problem is the other way around. Perfect at close distance and front focus at longer distances.
    Scott

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    Re: Front Focusing Summilux 75

    I know this: the lens has been shimmed for wide-open at infinity. If the focal length is too short, then the throw of the lens from infinity to closest range is too long and the objective is too far from the image plane. The lens will front-focus at close range, and stopping down will shift the focus towards infinity. The Summarit 5cm F1.5 works this way. Of four that I have examined, all were 51.1mm focal length- below what the RF of the Leica is calibrated for, and none used an indexed cam to correct the error. So they were optimized for F1.5 at infinity, and front-focus used wide-open at closest focus.

    On my Jupiter-3's, I optimize the focus for close-up and wide-open work. The focal length being too short caused the lens to focus past infinity. If the focal length is too long, and the lens is optimized for close-up/wide-open then the focus will fall short of infinity.

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    Re: Front Focusing Summilux 75

    Quote Originally Posted by paul25 View Post
    Now I'm in a state of panic......
    especially if this can't be corrected.......
    Paul, the experience I relayed in my post above was with a Leica 90mm E55 pre alph. and not with a 75mm Lux, so I would think you have some way to go prior to panicking, especially if an attempt to adjust it hasn"t been attempted yet.

    As for a 75mm lux being somewhat of a difficult lens to focus and/or adjust, I may (actually my dad) had just been lucky The new one of his I recently put up for sale ( and am still contemplating doing so again) focused perfectly wide open at all distances on a number of M9"s and M8.2"s, right out of the box, so not sure if all 75 Lux"s are difficult or not. Brian and others are right though...nailing focus wide open takes practice just as it does with all the Nocts and some other fast lenses. Keep us posted how adjustment of your lens works out. The 75mm Lux is a very unique lens in my opinion, especially in the way it draws an image. Some liken it to a well behaved Noct.

    Dave (D&A)

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    Re: Front Focusing Summilux 75

    Quote Originally Posted by paul25 View Post
    Now I'm in a state of panic......
    especially if this can't be corrected.......
    I had a Noctilux (modern one) which did this - I sent it to Leica and it was fixed.
    I'm pretty sure its the lens.

    all the best

    Just this guy you know

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    Re: Front Focusing Summilux 75

    Quote Originally Posted by paul25 View Post
    My Lux 75 focuses fine at close distance, but front focuses when with distant subjects.

    Can this be easily corrected?
    Yes it can I now had my 75 Lux for 18months, and yes it is so important to have the calibration right. Originally it would focus within the cusp of DOF at MFD, and at mid distances it was way out, and yet infinity is was OK.

    I have a M9-P, and a backup M9, both sync'd and properly calibrated. The calibration of lenses is non-linear, and most of the time can be adjusted by Leica service centers, without having to be sent to Solms. Once the calibration is right, the lens is so much fun to use, as it is so very sharp wide open, at all distances. There are instances where the lens cam needs to be modified/changed, and this of course is done at Solms.
    Last edited by CharlesK; 5th July 2012 at 19:16.
    Charles Kalnins
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    Re: Front Focusing Summilux 75

    Matching the index of the cam to the exact focal length of the lens will fix the problem. Conversely, changing the focal length of the optics to match the cam of the focus mount and changing the main shim also works.

    But if you have a supply of cams that are properly indexed for variations of the focal length- that's the way to go.

    Now I'm thinking of backing out the rear module of one of my 5cm F1.5 Summarits. The Summarit does not use a shim, no shim to reduce to correct the front-focus. It does not use an indexed cam. Back out the rear optics, increase the focal length, add a main shim. I want a Summarit that is optimized for F1.5 when used close-up.

    Great Thread!

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    Re: Front Focusing Summilux 75

    Thank you for all your inputs....

    I will most likely contact DAG for solving this problem, because I heard that Leica NJ charges more, and the service is not so good.

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    Re: Front Focusing Summilux 75

    Quote Originally Posted by paul25 View Post
    Now I'm in a state of panic......
    especially if this can't be corrected.......
    Paul, do to panic. I routinely send any used lens I buy to Leica NJ. Often it is to 6 bit code the lens, but included in the $230 for 6 bit coding is the checkover that Leica does in recalibrating your lens.

    Also remember that RF cameras probably would perform better if they were sent into Leica very couple of years, or sooner if the camera has experienced some bad bumps and bangs.

    I just noticed you are in NY so you can go over to Leica NJ in a flash.

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    Re: Front Focusing Summilux 75

    Okay, I just finished putting the 5cm F1.5 Summarit-M back together. Some quick fence post test: On the M9, the front-focus at F1.5 seems to be gone. All 4 Summarits that I've used front-focus at F1.5 and all were marked 51.1mm FL on the optics barrel, after removing from the focus mount.

    I moved the rear optics out by 0.2mm. Discovered that the shim from a Jupiter-8 worked perfectly. This has the effect of decreasing the distance between the rear element and the image plane which reduces front-focus, and increasing the overall focal length.

    The Summarit-M does not use an indexed cam, like the 75mm lens. I'm going to do a more thorough test on the M9, and will post back with success/failure.

    My thanks to the OP. I read on Dante Stella's site that the Summarit was optimized for F2.8 used close-up. I could confirm that testing the Summarits. No shim to adjust, and focal length slightly under the raditional 51.6mm. Never thought to move the rear module out on it until this thread.

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    Re: Front Focusing Summilux 75

    The test results look very promising.

    http://forum.getdpi.com/forum/leica-...pen-focus.html

    This Summarit can now be used from close-up to infinity at F1.5. No obvious aberrations sneaking into the image. The trade-off is that the lens will back-focus when stopped down, similar to a C-Sonnar optimized for F1.5.

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