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Thread: Mission Impossible: Fujinon f0.85 25mm on m4/3

  1. #1
    deep.space
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    Mission Impossible: Fujinon f0.85 25mm on m4/3

    Hello!
    Out of foolishness or ingenuity I bought a brand new Fujinon CCTV lens with an impressive f0.85 and 25mm, and c mount.
    Is it usable on any of the new m4/3 cameras out there? With how much modification? Specs are here:
    http://www.rmassa.com/specsheets/CF25L.pdf
    I am facing many hurdles, the most serious of wich is the back of the lens protruding 2 mm into the shutter of my g1.
    Here are the numbers:
    20.0mm m4/3 flange to sensor distance
    -17.526mm c mount lens to sensor distance
    = 2.5mm all c lens will have to be mounted with rear inside camera
    +9.6mm rear element of this fujinon lens
    =12.1mm space needed after flange (inside) camera
    -9.7mm flange to shutter baffle in g1
    =2.4mm space deficit
    -0.5mm can be shaved off from the back of the lens
    =1.9mm still needed

    Could someone please measure the flange to shutter baffle distance
    in the other m4/3 cameras like pen and gf1? Thank you
    (How much focus to infinity do I loose with those 1.9mm?)
    Bart

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    Senior Member pellicle's Avatar
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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    deep space ... plonk down about 40 bucks on one of these and see if that doesn't solve your problems

  3. #3
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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by pellicle View Post
    deep space ... plonk down about 40 bucks on one of these and see if that doesn't solve your problems
    Hi, thanks, I saw those and will have to buy one eventually. But that is the simple part of the problem
    Moi moi Bart

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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    With the dimensions shown, you won't get infinity focus and I would be surprised if you can even get the thread started. The lens also protrudes into behind the mount by over 9mm and it is quite possible there will never be enough clearance at the top and bottom of the MFT light box. I guess you have sort of figured that out.

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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Hi

    Quote Originally Posted by deep.space View Post
    Hi, thanks, I saw those and will have to buy one eventually. But that is the simple part of the problem
    Moi moi Bart
    I'm suspicious you're overcomplicating it ... plonk the lens on an adaptor and you can then see if it really does proturde into the shutter ... none of my C mounts do

    this is also a CCTV lens



    no obstructions, and should be the same spec as your lens.

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    Senior Member pellicle's Avatar
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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    for instance

    this is the amount of thread protrusion from the back of an RJ Camera adaptor of my Elgeet lens



    Its a sweet little lens



    details on it here.

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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Pellicle, You have not dealt with any lens with such rear protrusion as Bart is facing. Just because it is a c-mount lens does not not mean it is like the one you know.

    Bart, I think this lens is useless on m4/3rds. Wait for a cam with a more deeply recessed shutter (or without a mechanical shutter).

    Do you know if the 25/0.85 cover the whole m4/3rds frame at infinity?

  8. #8
    deep.space
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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by Vivek View Post
    Pellicle, You have not dealt with any lens with such rear protrusion as Bart is facing. Just because it is a c-mount lens does not not mean it is like the one you know.

    Bart, I think this lens is useless on m4/3rds. Wait for a cam with a more deeply recessed shutter (or without a mechanical shutter).

    Do you know if the 25/0.85 cover the whole m4/3rds frame at infinity?
    Vivek, I suspect you are right, that it is useless, but I will check all
    possibilities before I surrender

    The lens is quoted as having a 1" image. (same as the Navitar 0.95).
    So I will use 3/3 of the 4/3 sensor
    The remaining outer 1/3 will have strong vignetting (?) .

    As for the more deeply recessed mechanical shutter, that is what
    I'm trying to discover on cameras other than g1. Do they have the same
    shutter construcion? The gf1 for example, is it the same engine with
    a different chassis?

    B.

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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by Vivek View Post
    Pellicle, You have not dealt with any lens with such rear protrusion as Bart is facing. Just because it is a c-mount lens does not not mean it is like the one you know.
    hey ... I know two

    I have an Elgeet and and this computar





    sorry I can't be of help on this issue


  10. #10
    deep.space
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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by PeterB666 View Post
    With the dimensions shown, you won't get infinity focus and I would be surprised if you can even get the thread started. The lens also protrudes into behind the mount by over 9mm and it is quite possible there will never be enough clearance at the top and bottom of the MFT light box. I guess you have sort of figured that out.
    I have noticed from internet pictures that the light box (I presume you mean
    the space in front of the shutter and behind the lens) is different from model to model of m4/3.
    The gf1 having the biggest light box. There shouldn't be any problems width wise on gf1, only length wise for accomodating the lens' back cilinder.

    B.

  11. #11
    deep.space
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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by pellicle View Post
    hey ... I know two

    I have an Elgeet and and this computar





    sorry I can't be of help on this issue

    Thanks for having answered

    B.

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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Bart, AFAIK, there isn't a camera at the moment that will allow the (full) use of the Fujinon 25/0.85. I would suggest that you keep it (it is discontinued) until the right camera comes along.

    I have a museum piece optics in an UV-Planar 62/2. It covers ~32mm circle but the back focus is <1cm and also has a large (wide) rear element. I can't use it on any digital camera, at the moment, either.

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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by deep.space View Post
    The lens is quoted as having a 1" image. (same as the Navitar 0.95).
    So I will use 3/3 of the 4/3 sensor
    The remaining outer 1/3 will have strong vignetting (?) .
    Four Thirds and Micro Four Thirds gets its name from the aspect ratio of the standard frame, i.e. 4:3. The standard image area is approximately 17.3mm x 13mm. A 1" format c-mount lens gives full coverage. The reason for vignetting with a large number of c-mount lenses is that most are produced for either 1/2" or 1/3" sensors. Most CCTV lenses are only 1/3" for example.

    Most older c-mount lenses were made for a 16mm cine frame size of 10.26mm x 7.49mm although other variations such as Super 16 and Ultra 16 are marginally wider (up to 12.52mm wide for Super 16). These other formats get the extra width by only having perforations on one side of the film while the original 16mm film format had double perforations.

    The real problems are not the coverage as a 1" format lens will do just fine.

    Your real problems are the intrusion into the lightbox and the diameter of the base of the lens.

    As the Micro Four Thirds mount is around 20mm from the sensor and a standard c-mount is just over 17.5mm, the adaptors for MFT must be recessed into the camera body. Looking to the outside part of the c-mount adapters, that's why you see several concentric recesses in the mount. The diameter of your lens is 56mm which seems to be pretty much consistent to the mount just won't fit. Scroll down and you will see the measurements that fit without marching the back of the lens... http://cgi.ebay.com.au/C5-type-TV-Bo...item4a9bd9af09

    Note what it says...

    "The rear lens largest diameter is 37 mm that is best for infinity location.
    If the diameter is over 37 mm , less than 49 mm.
    It can fit the adapter,but can not to infinity. "


    I expect that you could modify the lens with a bit of machining to fit but would still have an issue with the rear intrusion into the lightbox.

    If you want to use the lens purely for macro work, you could try something like the Robot flange that fits into a modified c-mount adapter. The Robot brand of cameras used the same c-mount thread but had a distance to the film plane of 28mm. That's adding around 9.5mm distance between your lens and the sensor. I cannot give you any idea of how this will affect focusing distances, but you would have an incredibly fast macro lens (with very little depth of field which isn't good in macro).

    This is the Robot flange... http://cgi.ebay.com.au/ROBOT-to-M4-3...item4a9bd9ae2f

    It needs a different version of the c-mount adapter, the W1 which has a 3 tiny grub screws to lock in the flange. There aren't any up on the hawks_factory site at the moment but they cost a little more than the standard c-mount adapter. You cannot use the Robot flange without the modified adapter as there would be nothing to hold it in place.

    Cheers

    Peter
    Last edited by PeterB666; 30th October 2009 at 05:58.

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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by PeterB666 View Post
    Four Thirds and Micro Four Thirds gets its name from the aspect ratio of the standard frame, i.e. 4:3. The standard image area is approximately 17.3mm x 13mm. A 1" format c-mount lens gives full coverage. The reason for vignetting with a large number of c-mount lenses is that most are produced for either 1/2" or 1/3" sensors. Most CCTV lenses are only 1/3" for example.
    Peter, the 4/3 size does not refer to the ratio (which is the most common one for compact digital cameras) but harkens back to the old TV vidicon tube sizes, in which the size refers to the diameter of the glass tube surrounding the 'sensor'. That's what all the rest of those crazy sizes, like 1/2.5" and things of that nature refer to.

    So 4/3" actually gets you a true sensor size that is even slightly less than 1" diameter (about 22.5mm), and a video lens for 1" sensors actually covers only about a diagonal of 16mm.

    When discussing a film lens which is intended for a movie film camera, the coverage mentioned is usually the actual size in X x Y or in diameter.

    So when ordering or discussing a Video lens, make sure that it's understood whether the coverage is in terms of the vidicon size, in which case the actual coverage diameter is approximately 2/3, or in actual image size.

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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by deep.space View Post
    Hello!
    Out of foolishness or ingenuity I bought a brand new Fujinon CCTV lens with an impressive f0.85 and 25mm, and c mount.
    Is it usable on any of the new m4/3 cameras out there? With how much modification? Specs are here:
    http://www.rmassa.com/specsheets/CF25L.pdf
    I am facing many hurdles, the most serious of wich is the back of the lens protruding 2 mm into the shutter of my g1.
    Here are the numbers:
    20.0mm m4/3 flange to sensor distance
    -17.526mm c mount lens to sensor distance
    = 2.5mm all c lens will have to be mounted with rear inside camera
    +9.6mm rear element of this fujinon lens
    =12.1mm space needed after flange (inside) camera
    -9.7mm flange to shutter baffle in g1
    =2.4mm space deficit
    -0.5mm can be shaved off from the back of the lens
    =1.9mm still needed

    Could someone please measure the flange to shutter baffle distance
    in the other m4/3 cameras like pen and gf1? Thank you
    (How much focus to infinity do I loose with those 1.9mm?)
    Bart

    Another thing to consider is the angle of incidence of the light rays, even on-axis. For f/0.85 the outer rays coming from the edge of the exit pupil hit the sensor at about 36 degrees incidence angle. If the sensor can't handle such a steep angle then you won't really get any response at f/0.85. In other words, as you stop down the exposure won't change as you expect it to.

  16. #16
    deep.space
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    Red face Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by PeterB666 View Post
    Four Thirds and Micro Four Thirds gets its name from the aspect ratio of the standard frame, i.e. 4:3. The standard image area is approximately 17.3mm x 13mm. A 1" format c-mount lens gives full coverage. The reason for vignetting with a large number of c-mount lenses is that most are produced for either 1/2" or 1/3" sensors. Most CCTV lenses are only 1/3" for example.

    Most older c-mount lenses were made for a 16mm cine frame size of 10.26mm x 7.49mm although other variations such as Super 16 and Ultra 16 are marginally wider (up to 12.52mm wide for Super 16). These other formats get the extra width by only having perforations on one side of the film while the original 16mm film format had double perforations.

    The real problems are not the coverage as a 1" format lens will do just fine.

    Your real problems are the intrusion into the lightbox and the diameter of the base of the lens.

    As the Micro Four Thirds mount is around 20mm from the sensor and a standard c-mount is just over 17.5mm, the adaptors for MFT must be recessed into the camera body. Looking to the outside part of the c-mount adapters, that's why you see several concentric recesses in the mount. The diameter of your lens is 56mm which seems to be pretty much consistent to the mount just won't fit. Scroll down and you will see the measurements that fit without marching the back of the lens... http://cgi.ebay.com.au/C5-type-TV-Bo...item4a9bd9af09

    Note what it says...

    "The rear lens largest diameter is 37 mm that is best for infinity location.
    If the diameter is over 37 mm , less than 49 mm.
    It can fit the adapter,but can not to infinity. "


    I expect that you could modify the lens with a bit of machining to fit but would still have an issue with the rear intrusion into the lightbox.

    If you want to use the lens purely for macro work, you could try something like the Robot flange that fits into a modified c-mount adapter. The Robot brand of cameras used the same c-mount thread but had a distance to the film plane of 28mm. That's adding around 9.5mm distance between your lens and the sensor. I cannot give you any idea of how this will affect focusing distances, but you would have an incredibly fast macro lens (with very little depth of field which isn't good in macro).

    This is the Robot flange... http://cgi.ebay.com.au/ROBOT-to-M4-3...item4a9bd9ae2f

    It needs a different version of the c-mount adapter, the W1 which has a 3 tiny grub screws to lock in the flange. There aren't any up on the hawks_factory site at the moment but they cost a little more than the standard c-mount adapter. You cannot use the Robot flange without the modified adapter as there would be nothing to hold it in place.

    Cheers

    Peter
    Hi Peter, thanks for the info, yes some machining would be required on the lens, because it is very wide. The intrusion into the lightbox, is getting better, in the sense that I repeated the measurements with a Olympus PEN and there's additional 0.5mm space in the lightbox, which gets the "space deficit" down to 1.4mm .
    Also the intruding cylinder can be shaved off a little more. In fact the lens is slightly recessed inside inside the cylinder. There is 1.5 mm height difference between the cylinder and the lens
    So shaving off a total of 1mm would get my "space deficit" for infinity down to about 0.9mm... !!
    I think I'll get a Navitar 0.95 25mm, and wait until the appropriate camera comes out.
    Bart
    Last edited by deep.space; 31st October 2009 at 05:21.

  17. #17
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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by brianc1959 View Post
    Another thing to consider is the angle of incidence of the light rays, even on-axis. For f/0.85 the outer rays coming from the edge of the exit pupil hit the sensor at about 36 degrees incidence angle. If the sensor can't handle such a steep angle then you won't really get any response at f/0.85. In other words, as you stop down the exposure won't change as you expect it to.
    True. I've read somewhere that m4/3 was possible because of a lower "wall" between pixels on the sensor which allowed a higher incidence angle of light because of the 20mm distance between sensor and flange.
    I think the only way to discover if it can handle the 36 deg is to try, but as you point out this is another potential problem
    Bart

  18. #18
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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    Quote Originally Posted by henningw View Post
    Peter, the 4/3 size does not refer to the ratio (which is the most common one for compact digital cameras) but harkens back to the old TV vidicon tube sizes, in which the size refers to the diameter of the glass tube surrounding the 'sensor'. That's what all the rest of those crazy sizes, like 1/2.5" and things of that nature refer to.

    So 4/3" actually gets you a true sensor size that is even slightly less than 1" diameter (about 22.5mm), and a video lens for 1" sensors actually covers only about a diagonal of 16mm.

    When discussing a film lens which is intended for a movie film camera, the coverage mentioned is usually the actual size in X x Y or in diameter.

    So when ordering or discussing a Video lens, make sure that it's understood whether the coverage is in terms of the vidicon size, in which case the actual coverage diameter is approximately 2/3, or in actual image size.
    Check this as well

    http://www.dpreview.com/news/0210/02...ensorsizes.asp

  19. #19
    D.Keymn
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    Mission Impossible Fujinon f0 85 25mm on m4/3

    Great vid OD,
    Now, we want to see you do the same mission with the Trex 250

    Steve.

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    Re: Mission Impossible: Fujinon f0.85 25mm on m4/3

    What happened with the Fujinon 25mm ? There is one up on ebay and I was curious.

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