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Thread: Fujinon 12.5mm f1.4 CF12.5A modification

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    Fujinon 12.5mm f1.4 CF12.5A modification

    Finding a wide angle fast lens for the GH1 is a problem. There are simply none available. Vivek from GetDpi played around with the Fujinon 12.5mm f1.4 and modified it to get full coverage. This is my attempt to do the same.

    This attempt was referenced in these places.

    http://forum.getdpi.com/forum/showpo...2&postcount=39
    http://forum.getdpi.com/forum/showth...790#post234790

    Since I cannot post a gallery, I have put up the pics and the description over here.
    http://www.mishra.tv/wordpress/?p=150

    Tools used. DIY Rubber tool for unscrewing recessed lenses and a set of lens spanners. Not shown here but also used is a small screwdriver from a 2$ jewellers set of tools from DSE.

    Rear element. The rear element was removed with a lens spanner. The glass element is not attached to anything and will fall off, so be careful.

    Front element. The front element was first loosened with the lens spanner and then unscrewed with the rubber tool.

    Lens body and focus ring/hood. There are 3 small screws in the focus ring that come off with the jewellers screwdriver. Then the 2 parts easily separate.

    Top view of hood/focus ring and lens body. This view shows the brass helicoid (??) that is involved in the conversion. We can also see the shutter in the lens body.
    Last edited by zcream; 4th August 2010 at 06:05.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Now this attempt is stuck and I will wait for Vivek to answer my questions as I have absolutely no clue what he did.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Just for me to note down my query. I can reduce the distance between the front element and the aperture, or the rear element and the aperture.
    This is what I am waiting for - since I'm not sure what is ideal.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Move the entire front group closer to the diaphram. You need to rehouse the front group and get rid of the old metal housing. This is not an easy task at all...

    .. and I do not mean that lightly.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Hi Vivek. Great to hear back from you. My brother is actually biking around India at this time on an Enfield Bullet.

    I think I can file down 2mm from the housing to move it closer - thats the part above the threads. I dont think I have the expertise to make a new housing.
    I can try do it tomorrow. I also bought a sampling of other C-mount lenses, 8mm, 8.5mm and 6.5mm and I will try my approach on all of them one by them to see how it works out.

    Thanks for the tip!
    Quote Originally Posted by Vivek View Post
    Move the entire front group closer to the diaphram. You need to rehouse the front group and get rid of the old metal housing. This is not an easy task at all...

    .. and I do not mean that lightly.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    An Enfield Bullet is an antique rarity now (at least in the South).

    Everyone I saw has been riding a Honda or something...

    Good luck with your modification. But, IMO, it is perhaps better to wait for the rumored 14/2.5 of Pana that should show up within a couple of months.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Problem is that I really need the extra speed - I am shooting a film outdoors at night. I have no lighting and only work with street lights - so f1.4 is barely enough for my requirements.
    About the Bullet, there are 5 of them in a group. The bike does not work half the time, so I dont know the appeal anyway.
    I took out the front hood and now I have gone through 2.5mm. there is 2mm of thread left where the front element screws in. I will try some more - but its promising, there is a VERY small vignette left.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    I screwed up. I got impatient while reassembling the lens and broke the aperture blades. 100 bucks down the drain.
    Vivek,did you sand down the black metal housing all the way to the brass part ? I can temporarily use super glue to hold the front element in front of the helicoid, but I do not see any way to disassemble the part in front of the aperture any more. The helicoid and the housing seem to be glued together or screwed in a clever way that prevents disassembly.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    I ripped out all the aperture blades as some were cracked. Now I have an image which looks like the ones from the X-Ray lenses with strange glows all over. Perhaps I did not reassemble the lens properly. can someone who owns the lens let me know if the rear element is concave or convex ? And once I have that, I can work with the inner 2 elements for proper reassembly.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Have any of you tried putting a negative element in front of the lens? That should increase the back focus, allowing the entire lens to be moved out from the sensor. You would need a small extension tuve. Chromatic aberration will increase.

    I just picked up one of these. I might play with it. The vignetting is not so bad. The 12.5mm F1.4 is stated for use with 1" diagonal sensors, at least in literature. It seems to come close to the 4/3 EP2, which is larger than 1" diagonal sensor.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Okay- just discovered that 1" C-Mount format is computed by adding two sides, and not using the diagonal. So, the image circle for a 1" C-Mount lens is 16mm.

    The Negative Element in front did not work. Moving internal elements around is going to change the focal length.

    I suspect the rear group would have to be replaced with one with a much larger diameter, which is the difference with some half-frame vs full-frame lenses. Specifically, the CZJ 5cm F1.5 Sonnar in Contax mount vs Arriflex mount. But that's "just a guess" to increase coverage on this lens.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Vivek has had full coverage by moving the front element to the iris. And I could see the coverage increase as well.
    I treated the lens roughly while unscrewing it and then not reassemble it properly - but I can confirm that the image circle increases by moving the front element to the rear.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Just for the records:

    1. I did not move any elements (that would have been a disaster). I moved the entire front group.

    2. The FL did not increase, from what I could see.

    3. The lens' speed also did not become less.

  14. #14
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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Vivek, want to give a more detailed account of how you did that?

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    I should edit - I moved the front group (of at least 2 elements) towards the aperture blades.
    The front group threads into the lens body. You need to remove the hood and the focus ring.
    I filed down the lens body almost all the way.
    Vivek possibly did away with the the threaded holder completely and built a new housing.

    Look at my pics linked in the first post. I got full coverage and moved ~3-4mm closer to the body.
    Wish I had bought 2 lenses to play with. Now I have to wait for another lens to come through.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    http://www.surplusshed.com/pages/item/l3943.html

    has anyone tried the Computar 12.5mm F1.3? It is described as being for 1" C-Mount, the same as the Kowa. $25 at surplusshed.com.

    My Kowa 12.5mm F1.4 is an older design, chrome housing and different mechanics. I might take it apart, but will wait for the Computar to arrive first.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    vivek commented on the computar. There wasnt enough separation between lens groups to bring them together

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Okay- has anyone tried a Century Paragon Optics HI-G Camera Lens f1.5/13mm?

    http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWNX:IT

    For $10, I'm taking a shot at it. The front filter size is 55mm. I'll find out what size image circle it forms. I can hack it onto an adapter if it has enough clearance. Century Optics made a number of lenses for the scientific/technical market.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    I have the Hi-G lens. It has a custom mount and is difficult to take apart. Not enough coverage.

    BTW I got the elements right and the 12.5mm works brilliantly. Nearly full coverage. I used the original assembly and just filed some thread away.

    Brilliant!
    Buying a few more off ebay..

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Zcream

    Well done! Any samples with vignetting?

    Thanks!

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    In the end, the rear needed a little machining as well. I will post pics of exactly what I modified later.
    Here are some quick pics of contrasty regions - all *WIDE* open at f1.4. A bit soft but I dont think many lenses are sharp at 1.4 that wide.
    Picasa Album

    And some of these snapshots.




  22. #22
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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Any updates?

    I would really like to use a relatively cheap wide-angle lens on my cam.
    Last edited by jwestra; 31st August 2010 at 11:01.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification


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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Not bad at all.

    Can you show some pictures of the modified lens or the modification. Your aperture is completely broken, right?

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Yes the aperture is broken. I think that this is causing the sharpness loss in the corners. I bought another lens off ebay - this time I will leave the aperture intact. I think this lens has a lot of potential. My next mod will be perfect.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Quote Originally Posted by zcream View Post
    Yes the aperture is broken. I think that this is causing the sharpness loss in the corners. I bought another lens off ebay - this time I will leave the aperture intact. I think this lens has a lot of potential. My next mod will be perfect.
    Not to douse your enthusiasm and hope...

    It will always look to be of "having potential" and will never cover the frame fully (will illuminate it though). It will be soft until ~f/5.6. The CA is very troublesome and can not be corrected.

    These are some the reasons why I keep saying that I would wait for the rumored 14/2.5.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Hi Vivek. For my purpose its fine. I need to shoot some dancers in a park lit only by streetlights. I need wide and fast. I can add a mask in post to brighten the corners and remove the vignetting.
    I can also avoid the off-centre softness by keeping the dancers around the middle.

    If I get this right, even the new copies I will get have this problem with softness ?? Is that right ?
    Would you consider posting a brick wall picture with your lens as well ?

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification


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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Nice. I can see the edge distortion but you seem to have got full coverage - not even the mild vignetting I get.
    I would love to see pics of your housing and your solution for the focus end stop screw.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    I have this same lens and I'd like to attempt this modification.

    I'd like to see more photos of what you've done.

    I follow you until the point where the focus ring is removed and you can see a portion of the brass helicoid the focus ring set screws tighten onto... but your photos and descriptions end there.

    From that point, what I see inside the lens is a c-clip which holds what I would call a circular mask, and under that I can see the aperture blades.

    I have removed the rear element and the rear lens group as well.

    I'm guessing the next step is to remove the c-clip and the iris assembly?

    It's looking like a near complete disassembly in order to get to the part of the helicoid that needs modification.

    Are the focus ring markings accurate afterward?

    Any more information/photos would be greatly appreciated.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    I have updated the gallery in the first post. However, this is the quick summary of what I changed in pics.








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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Focus is accurate, nothing changes except a larger image circle. I am getting delivery of a couple more lenses so I can modify them.
    I like this lens and may well end up with 3-4 modified copies. Possibly a couple would go on ebay.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    thanks for the update!

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Thanks for that.
    Now it makes sense.
    Can you suggest how many millimeters need to be removed?
    So I think there isn't really a need to remove the rear element.
    I found out what you mean by the rear element not being attached. It's actually the lens group 2nd to the rear. Mine came tumbling out and luckily I caught them in a lens cloth in their correct order. I was able to replace them with the aid of a drinking straw and 'manual suction' for lack of a better phrase. So beware, anyone, when you remove the rear element, the lens group just above it will fall out if you tip the lens.
    Shame about having to loose the hood.
    By the way, I think you beat me to those other fujinons. Was it Calkovsky you got them from?

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Hey there, any plans to sell off some of these modified 12.5mm s? I'd be interested in one.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    In terms of removing metal - the rear is about 2mm. When you look at the adapter next to the lens you will know what I mean.
    Theres lots of meat so remove 3mm to be sure if you want.

    The front part, the more you remove, the closer you will be to full coverage.
    However, if its too thin you cannot attach the focus stop. So machine some off, reattach the focus stop and repeat process.

    Quote Originally Posted by ekoe View Post
    Thanks for that.
    Now it makes sense.
    Can you suggest how many millimeters need to be removed?
    So I think there isn't really a need to remove the rear element.
    I found out what you mean by the rear element not being attached. It's actually the lens group 2nd to the rear. Mine came tumbling out and luckily I caught them in a lens cloth in their correct order. I was able to replace them with the aid of a drinking straw and 'manual suction' for lack of a better phrase. So beware, anyone, when you remove the rear element, the lens group just above it will fall out if you tip the lens.
    Shame about having to loose the hood.
    By the way, I think you beat me to those other fujinons. Was it Calkovsky you got them from?

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Here is a video of the Christmas Light show in Sydney using the Fujinon 12.5mm. Taken with a GH1 in 1080p and the downconverted to 640x480 for youtube.
    http://www.youtube.com/watch?v=l4i1JFaqtAk

    It is heavily compressed so dont judge the quality by it. The original video is sharper in the center. The edges are soft, as Vivek mentioned,

  38. #38
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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Just thought I share what was a project that went stale many months ago. My piece, which is the same model as per the thread title differs in that I took it straight off an actual CCTV product. I dismantled it and repurposed a piece of metal to use as a rear mount, which it didn't have. The only real issue is that it cannot achieve infinity focus, which i reckon wouldn't take much to resolve- but I don't have the proper tools so I've given up. It would probably take a more forgiving c mount adapter, since I use the RJ adapter- i read that the dimensions aren't suitable and hawkeyes one might be better for this piece and maybe some shaving. When that happens I reckon the vignetting with get lesser as well.

    I will put this on sale next year for whatever it's worth, but these are the pictures shot on the GH-1 with a slightly larger sensor then the GF-1 so even more vignetting there.




    16:9


    3:2


    4:3


    1:1

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Raymond, I dont think you moved the front element closer. Try it, from the first post, and you will achieve nearly full coverage.

  40. #40
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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    I didn't, i have no idea how to begin dismantling it! I saw your pictures but it still leaves me uncertain. There are a few screws which seems to hold the front casing of the lens together. I'm not sure but i might try unscrewing it and seeing what happens anyway.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Hi guys. Just a mention that I am selling the modified 12.5mm Fujinon 1.4 lens. If anyone is interested in it, let me know. This is the fixed focus version as I took out the aperture blades to get improved low light. Then I could not put them back in.

    Here are pics taken with the modified lens (I think I used the GH1 for this, could also be the GF1)

    https://picasaweb.google.com/anmol.mishra/CF125A#

    Cheers!

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Hello zcream and others.

    As an update to this thread, I've developed a modification for the Fujinon-TV 12.5mm/f1.4 that results in near full sensor coverage of the m4/3 sensor in 4:3 mode. In 3:2 mode, there is just very slight vignetting. Focus marks remain the same, focal length remains the same, there is no softening of focus, just fuller coverage and less vignetting.

    I started with the modification suggested by Vivek and zcream, and extended it to include a total of 12 adjustments. The result is near full coverage in 4:3 mode with less vignetting than many 25mm c-mount cine lenses provide. I've even managed a way to use the original front housing, so the modification does not appear much different than the original unmodified lens.

    I am offering to perform this modification for others. Please PM me if interested. If you include your email address, I'll send along photo examples.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Here's before and after examples of vignetting:



    The finished modification:


    And a couple example photos:



    These are all taken with a GF1 in full sensor 4:3 mode, no cropping.

  44. #44
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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    Centrally, they look good, but these lenses (I have a Cosmicar) at 12mm fall apart at the edges badly. It can make for some really interesting out of focus shots if the edges are out of the focal plane, you can get that weird spiral-looking pattern with light sources with some.

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    Re: Fujinon 12.5mm f1.4 CF12.5A modification

    That's true... they are soft around the edges. On m4/3 you're seeing practically the entire taking area of these lenses, and some degree of softness, color fringing seems inevitable on such a wide angle lens.

    I don't know if the Cosmicar you have is for 1" video or not, but the Fujinon-TV lenses for 1" video tend to be very sharp (with the exception of the corners in the case of this 12.5/1.4), and also they don't have the swirly bokeh of many c-mount lenses.

    Considering the trade off of speed and cost vs. the drawbacks of the kit WA lenses, I really don't mind a bit of softness in the corners. Actually, I like it. But then, I also like just a hint of vignette.
    Last edited by ekoe; 18th May 2011 at 18:07.

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