Thread: Functioning Speed booster for Dragon 6K (working prototype)

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  1. #1 Functioning Speed booster for Dragon 6K (working prototype) 
    I know the subject of speed boosters for RED is a contentious one. I've read a lot of forum posts where responses range from "it's impossible, there's not enough room" to "why would you bother?".

    Well, it is possible. I've designed a custom CNC machined mount that houses a Metabones Speed Booster and achieves focus at infinity (without removing the OLPF or adjusting the back focus).

    Here are a few images:











    So, there are a few limitations.

    The first is that this was only possible with medium format lenses - in this case, Zeiss Jena Pentacon Six mount lenses. These were cheap & plentiful for me to test with, and also had one of the longest flange focal distances (74.1mm). Based on this prototype, it should also be possible to design a working speed booster mount for Hasselblad (74.9mm FFD) and possibly Pentax 645 (70.87mm FFD) lenses.
    However, as has been stated in other forums, this isn't possible with PL, Canon, Nikon, or other lenses with an FFD much shorter than 70mm.

    The second main limitation is that there are vignetting issues at 6K, depending on which lens is used. Strangely, I've found that longer focal length CZJ lenses (the 120mm Biometar & 180mm Sonnar particularly) are most prone to vignetting, especially at minimum focus. I can't be certain, but I suspect this vignetting is caused by the Metabones Speed booster, as it's not designed to cover a sensor larger than APS-C.

    Third limitation - the mount consists of three components - the glass from a Metabones E-mount speed booster (not BMCC), the CNC machined housing, and a Pentacon Six to Nikon mount adapter bolted together. I don't have the mechanical knowledge to design the P6 mount mechanism, so instead a P6>Nikon adapter is bolted into the front of the CNC machined housing with M4 grub screws. It's fairly strong, but if it were designed all together as one piece, it'd be rock solid.


    What's the point?

    This setup isn't practical for the vast majority of shoots. The widest Zeiss Jena lens for P6 is a 50/4, which becomes a 35/2.8 because of the speed booster. And as to be expected, these lenses aren't razor sharp, and some are extremely prone to flaring.
    I acknowledge all of the above, but I still think these lenses have a very attractive quality to them, and for some projects, that "character" may be the right thing.

    In addition, I'm hoping that this serves as proof of concept — if I can hack together this mount, a company like Metabones may be able to purpose-build a speed booster mount with an optic that covers the new 8K Weapon sensor - capturing the full image circle of these medium format lenses, competing with Alexa65. I think there's a market out there for medium format to full-frame speed boosters, Metabones & similar companies just don't know it yet.



    I didn't create this mount to make money, but if anyone is interested in one, I can look into the costs involved to get a batch machined. Also, if anyone is interested in collaborating, with mechanical or optical design knowledge, I'd love to further improve this mount beyond what I'm capable of alone.


    Thanks for reading. Feel free to share your thoughts, but again, I pre-emptively acknowledge that this isn't for everyone. If you can't see value in this, you are free to go back to your Master Primes :)



    Test footage:
    (Quick & dirty test to demonstrate the range of focus. 6K FF 5:1 compression, DC2 RG4, 320-640ISO, STH OLPF, Tiffen 4x4 Pola, all lenses are wide open, no sharpening or post adjustments. Made no attempt to rack focus smoothly.)

    50mm Flektogon f/4 (equiv 35mm f/2.8)
    https://vimeo.com/170758509

    80mm Biometar f/2.8 (equiv 57mm f/2) (This lens is unusually soft, I think it's a bad specimen. Also, reflections in the top right corner are caused by a gap between the lens and the mattebox & pola filter. Not caused by the focal reducer)
    https://vimeo.com/170758521

    120mm Biometar f/2.8 (equiv 85mm f/2)
    https://vimeo.com/170758529

    180mm Sonnar f/2.8 (equiv 128mm f/2)
    https://vimeo.com/170758566
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  2. #2  
    Senior Member Kwan Khan's Avatar
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    Nice...
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  3. #3  
    Senior Member Patrick Tresch's Avatar
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    I love the way you look at things. Thanks for your demos.

    Pat
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  4. #4  
    Senior Member Ben Roper's Avatar
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    Top work! So exciting to see someone playing with this concept.

    We've been shooting with some medium format glass (obviously just straight with no speed booster) for a few years now. I find the image characteristics really appealing, I just always wish that we could go wider. Our regularly used lenses are:

    Pentax 67 105mm f2.4
    Pentax 67 165mm f2.8
    Pentax 67 300mm f4

    Here's a little photo of the 105mm in use the other day...

    https://www.instagram.com/p/BGaY9nZCADi

    I'll be watching your progress with some interest - keep up the good work!
    Epic-X #7473
    www.rapturefilm.com
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  5. #5  
    Senior Member Jacek Zakowicz's Avatar
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    You need to watch two things:
    Vignetting and image quality. Yes you can move it and get things in focus but your image quality would be severely affected from my experience. The important aspect of speed booster is IMPROVED image quality/sharpness at the cost of space and coverage circle. When you change the location of the glass from what I have seen the image quality goes sideways very quickly....
    Jacek Zakowicz, Optitek-dot-org, jacek2@optitek.org
    Professional Broadcast and Digital Cinema Equipment
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  6. #6  
    Great work Josh! Keep up the good work.
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  7. #7  
    Senior Member Patrick Tresch's Avatar
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    Quote Originally Posted by Jacek Zakowicz View Post
    When you change the location of the glass from what I have seen the image quality goes sideways very quickly....
    Hello,
    What do you mean by "location"? The position in the mount or the provider of the lens?
    Thanks

    Pat
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  8. #8  
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    Great work! That's the way to go. About the vignetting issues, it's pretty safe to assume this is caused by the speedbooster optics. Thats where the Kipon Baveyes comes to mind (made for Hasselblad to Sony E FF). Unfortunately this thing hasn't popped up for sale so far.

    Also, there are different speedbooster optics. Those optics from the BMPCC version would be interesting for smaller resolutions on RED. So, user-exchangeable optics probably aren't possible, right? ;)
    Maik Mueller || http://www.maikmueller.art
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  9. #9  
    Senior Member Jacek Zakowicz's Avatar
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    Quote Originally Posted by Patrick Tresch View Post
    Hello,
    What do you mean by "location"? The position in the mount or the provider of the lens?
    Thanks

    Pat
    both the speedbooster optics (location)and the lens location have to change in order to achieve focus.
    Jacek Zakowicz, Optitek-dot-org, jacek2@optitek.org
    Professional Broadcast and Digital Cinema Equipment
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  10. #10  
    Thanks for your responses guys

    Maik, swapping out the focal reducer optic is relatively easy to do. The Metabones E-mount optic is held in there by 8x M3 grub screws, which you can tighten by reaching an allen key in from the outside of the mount (there are holes in the outer cylinder to allow the allen key to reach the inner cylinder). I'm not sure how small the BMPCC optic is, but if it's in a similar sized housing it'd be easy enough to swap it in. If it was significantly smaller, you'd just need longer grub screws, and it would become trickier to ensure that the optic was perfectly centred.

    Jacek, I'm also curious about what you mean by moving the location. The speed booster shortens the flange focal distance, which necessitates changing the position of the lens, bringing it closer to the sensor - but surely this is true in all cases where a speed booster is in use?
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