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Thread: Navitar 25mm f0.95 conversion tutorial

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    Navitar 25mm f0.95 conversion tutorial

    I made a picture tutorial for people wanting to convert the Navitar 25mm f0.95 lens. I cannot copy the pics over fron my site -can anyone help me ?
    http://www.mishra.tv/wordpress/?p=108
    Navitar c-mount 25mm f0.95 conversion to micro 4/3

    Navitar lens before machining

    Remove 3 screws with a jewellers screwdriver and remove the the rear element ring.

    Picture of the second rear element ring.


    Use a wet sandpaper. Put some water on it and rub the second rear element in a figure 8 motion. I had to stop and test during the machining – the reader can machine it until the very edge of the screw hole.

    Closeup of the second rear element.

    Put the 2 rear elements back on the lens and put the screws back on.


    A picture of the finished lens. I tested it with the RJ and the Henry adapter. The focus ring now moves all the way across the near to far range. However, I still cannot achieve infinity focus – this problem is due to an incorrect focal flange distance. The lens is too far away from the sensor. How do I solve this ?

    Navitar lens
    As a part of shooting our film – Fountains, there are a lot of nighttime location shots. As we are operating on a small budget, we do not use lights, and require fast lenses. The Navitar 25mm f0.95 matches with the GH1 and GF1. However, in the original form the focus rings pushes against the adapter 1/3rd through its useful range. Here are some pics about how I machined this lens to fit the RJ and the Henry c-mount m4/3 adapters. At this time, I still cannot obtain infinity focus – this seems to be due to the focal distance being incorrect.
    Hudson has a similar mod here, but no description and the pictured lens is a Leitz.
    http://forum.getdpi.com/forum/showpo...9&postcount=29
    At this time, the focus ring moves across its entire range.

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    Re: Navitar 25mm f0.95 conversion tutorial

    zcream, A couple of observations:

    1. You are sanding down an aluminum ring and not a (glass) element.

    2. The picture that Hudson showed is that of a Navitar 25/0.95 that has a Leitz sunshade (hood) attached to it.

    To get infinity (CAUTION!):

    You need to unscrew the retaining ring of the rear most element and glue that element in place (the retaining ring is not screwed back after this operation). Apply epoxy on the outside (rim) and without it touching any of the glass surface or creeping into the glass and take care not to flip the rear element (easy to flip!) before fixing it this way. This one looks simple but it is easy to screw up and ruin the lens forever!

    Good luck!
    Last edited by Vivek; 18th July 2010 at 11:06.

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    Re: Navitar 25mm f0.95 conversion tutorial

    Hi Vivek, zcream, why go through all this trouble when a senko 25mm 0.95 fits without modification? is the navitar 25mm 0.95 a better lens than the senko? I am undecided between the 2 lenses.

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    Re: Navitar 25mm f0.95 conversion tutorial

    Hmm.. Paparazzi666,

    I bought the Senko and the Navitar > an year ago only to find out that they are different lenses.

    If I had known that you knew that then, I would not have bothered buying them.

    An Angenieux (type M2) 25/0.95 is a much better lens. A SOM-Berthiot Cinor 25/0.95 is even better (full coverage).
    Last edited by Vivek; 18th July 2010 at 11:34. Reason: typo

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    Re: Navitar 25mm f0.95 conversion tutorial

    ah yes, ange and SOM 0.95. they are now going for an arm and a leg on ebay. they cost more than the ep2 with vf2 and 17mm lens. the fun with c mount lenses for me has been getting fast lenses cheap. although i have been buying stuff that dont work and wasted lots of money sigh...its a wild wild west out there when it comes to c mount stuff.

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    Re: Navitar 25mm f0.95 conversion tutorial

    Quote Originally Posted by paparazzi666 View Post
    they are now going for an arm and a leg on ebay. they cost more than the ep2 with vf2 and 17mm lens.
    If they (one lens that is) are just more than that combo, that is an excellent buy. Worth every peso.

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    Re: Navitar 25mm f0.95 conversion tutorial

    Hi Vivek. Is the rear retaining ring cemented on ? It seems very stiff and hard to remove. Just wondering if I have to dissolve the glue with acetone or something similar. However, I dont want the solvent getting inside the lens

    Also, when you say glue the rear element - what am I gluing it to and what glue is being used ?

    The rear element is not blocked from moving and can move through the adapter. Would you consider elaborating on how removing the rear ring affects infinity focus ?
    Last edited by zcream; 18th July 2010 at 17:10.

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    Re: Navitar 25mm f0.95 conversion tutorial

    Put the lens on a table (sideways) and dribble one drop (no more) of acetone (nail polish remover) on the outside of the retaining ring. After that, let the lens sit vertically with the front facing upwards. After ~10 mins, use a hairdryer (cautiously) to warm up the retaining ring.

    You should be able to unscrew the retaining ring (while doing this the lens should be on a table with the front side facing the table surface). Once the ring is removed, the rear glass element (a single piece of glass) is not secure and that needs to be secured by epoxy.

    Perhaps Hudson could show a picture. I am sorry that I am pressed for time now.

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    Re: Navitar 25mm f0.95 conversion tutorial

    DONE! Perfect conversion. Thanks to Vivek and Hudson. Since I cannot edit the first post anymore - I have put up a detailed tutorial in the link in the first post. I am puzzled about why the rear retainer had to be removed. It was not being blocked in any way.
    Strange!

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    Re: Navitar 25mm f0.95 conversion tutorial

    Hi Vivek,

    So I'm really interested in the SOM Berthiot one. Is there much conversion needed to be done? Seeing that the Angie now is around $1200, I guess it's reasonable for this Berthiot to be about $1500?

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    Re: Navitar 25mm f0.95 conversion tutorial

    The movie version of the SOM 25/0.95 does not need any conversion.

    The CCTV version (some samples) do need a ~1mm rear shaved off (best done through a machinist) to achive infnity focus with a Hawk adapter.

    Worth every cent, IMHO and is a bargain, especially compared to the Angenieux 25/0.95 Type M1 lens.

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