Thread: Nikon BMCC Speedbooster with 24mm 2.0

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  1. #1 Nikon BMCC Speedbooster with 24mm 2.0 
    Hello everyone,

    I picked up a Nikon F Metabones BMCC Speedbooster up last fall to use on the BMPCC4k for a more full frame feel. Now I have finally come around to testing my set of Nikon AIS lenses with it and a few lenses feel a little tight. However, the 24mm 2.0 Nikon AIS lens doesn't fit at all. On the Metabones website the only not compatible lens is 20mm 2.8, which fits (albeit a little tight). Anyone have any advice on how to make the 24mm fit?

    Much appreciated!
    Paul
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  2. #2  
    Senior Member DPStewart's Avatar
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    Yup, Some of my AI-S lenses are really tight too.

    I don't have the the 24mm, I have the 28mm so I don't personally have this problem, but there were some folks here back a couple years ago who sorted out a few of the "resistant" lenses on speedboosters.

    From what I remember - it's a matter of a tab.
    One or two of the Canon's can have the problematic tab cut off, or the rear lens enclosure cover removed, and then they work.
    I've done this with a couple Canon lenses. You just have to be careful with them afterwards.

    Okay, I'm working from memory here so this may not be exactly it - I may be confusing a couple different lenses.
    There is ONE of these AI-S lenses that CAN have the problem tab cut off (although it might make it's normal use back on a Nikon stills camera difficult or permanently limited) and there is one lens that you basically have to break in order to get it on na speedbooster. Break as in 'you've pretty well wrecked it.'

    I think the 24mm is the one that just needs a tab shaved down.

    Ruben De Boer (member here) just sold a cine-modded set of AI-S lenses and he had a 24mm, but I'm not positive it was the f/2.0. He might know the exact specifics.
    Last edited by DPStewart; 06-17-2019 at 03:15 AM.
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  3. #3  
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    If it's an exposure lever that juts out too far you can shave it with a dremel tool while covering the rest of the lens from debris.

    Not sure about the engineering of Nikons, but you may be able to just remove it by going into the rear of the lens. I just removed the same type of lever on a Cosina 19mm. Only took 10 minutes and a few screws. Was also able to de-click the aperture.

    Though I might be a little wary of such an operation on a lens 8 times the price..
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  4. #4  
    Thank for the replies!

    @GeranSimpson I don't think it is the aperture lever, but rather a fixed part on the rear of the mount that is protruding. You can see it on the picture below. I am not quite sure what the function is.

    KEN_9417-1200.jpg

    @DPStewart Metabones recommends to remove the rear enclosure in case of the 20mm 2.8 (which fits in my case strangely enough). So this would be an option here as well, however I am worried about leaving it susceptible to dusk entering the rear of the lens that way. Do you have any idea about the function of the tab? I wouldn't be opposed to removing it as long as it doesn't render useless with other cameras, but then again I am not sure what the tabs function is in the first place..
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  5. #5  
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    That part appears to be the same on all the Nikon AIS lenses, not sure this is your issue. Did you put the Speed Booster lever in the max f/stop position (7) before attempting to mount the lens? The lens mount flange might also be too thick or the SB set too tight around the flange. The lens should fit right, but you should not have to force it in either.

    Try mounting the lens to the SB without the SB attached to the camera, so you have a better feel for what is going on. Also, check that little tab sticking out from the side of the lens mount at 3:00 on your photo, is that preventing the lens from seating in the SB?
    Cheers
    Last edited by Denny Smith; 06-26-2019 at 12:13 PM.
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  6. #6  
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    I used a vintage Nikon cinema converted set before with the Micro+Speedbooster. The 24mm was the only one that wouldn't fit on the Metabones. Coincidentally it was the only one that didn't appear shaved-down. Even trimmed the other lenses were a really tight fit and left marks on the felt.
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