Thread: Focus issues on BMMCC with Tokina 11-16mm DX II at 11mm

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  1. #1 Focus issues on BMMCC with Tokina 11-16mm DX II at 11mm 
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    Hello everybody,

    I'm posting over here as a last resort, meaning that I really don't know what's causing the issues for my BMMCC and Tokina 11-16mm ATX-Pro DX II. I've tested the lens on a Canon 200D, the photos are the ones made with that camera. At 11mm the lens is causing massive CA, no issues regarding focus on the Canon. I've went to a Canon 6D and 5D mkII, this resulting only in the expected vignetting but no CA whatsoever or any focusing issues, maybe I'll upload the photos from them later. When mounted on my BMMCC with the dumb adapter from FOTGA EF->M4/3, the lens could focus to 0.5m(the lens shows 0.3m on the distance ring) when using the 16mm, going to 13mm..the focus starts to go further and further away, by the time I reach 11mm there no control on the focus..it's somewhere between 3m-2.5m. There are absolutely no issues when using Canon L lens with this adapter on the BMMCC, only with this lens(until now..jeez). I'm trying to figure out if it's from the adapter, or the moving optical part from the Tokina. On the Canon L lens, there's a fixed lens(diopter or..) that's between the moving optical part and the mount, the Tokina doesn't have this. Any experience with this issue..btw, if it's something know, it really wasn't to be found, at least by me. I also didn't understand if this is front or back focus issues, so accept my excuses as I've just bought the camera a month ago, and besides me being ecstatic every time I'm using this camera, I'm still learning a lot about it. Any help is appreciated.

    Cheerz,

    Sorin

    P.S. Click to download the photos and the ProRes clip.
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    Last edited by mikus; 04-20-2018 at 04:20 PM.
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  2. #2  
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    Changing sensor size will change the CA because I believe it's all about the angle/ path the light takes to hit the sensor.

    For the focus issue I'd have to blame the adaptor since the lens works fine when it's not a factor, all be it on different cameras.

    It'd be best to find someone local that will let you use their adaptor or speed booster.
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  3. #3  
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    True, I also think the adapter is the issue. But going from a large sensor to a smaller sensor will not increase the CA. Going the other way round and using the outer edge of the image circle would possibly bring the edge fringing into View and the increased CA. I just checked by Micro Camera and Tokina 11-16 (Duclos mod version) and no difference in CA or focus when zooming from 16 to 11mm. I will test this on my MFT camera tomorrow to see if any CA show up on the edges.
    Cheers
    Last edited by Denny Smith; 04-27-2018 at 01:33 PM.
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  4. #4  
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    Well, the thing is I don't have anyone with a different adapter or SpeedBooster for now. Maybe I'll try my chances at some rental shops on Monday and see if with the SpeedBooster the issue is still appearing. Denny, do you have the EF or PL version of the Duclos Tokina? If you have the EF, does it have the rear optic element moving? And if so, do you have another diopter between the mount and moving element, since it's a modded lens? And if it's the EF mount, do you use any adapter part from Metabones? I've uploaded the photos from the Canon 6D. There's no CA as shown on the Canon 200D and the sensor on the 200D is the same size as 7D(different sensor resolution tough), APS-C as the lens is made for(which makes the CA even more misterious).

    Click to download CR2 photos made with Canon 6D.
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  5. #5  
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    Many cameras have lens profiles that automatically correct known deficiencies. If you're taking still one camera might just be a bit better than the other at correcting it?
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  6. #6  
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    Mikus, I have the PL version, and the rear element moves when the lens is zoomed, I looked after reading your first post.
    Last edited by Denny Smith; 04-27-2018 at 01:33 PM.
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  7. #7  
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    So far I haven't managed to find any issue with the lens on Speedbooster so...any adapter that you'd recommend to use with Tokina and BMMCC, that doesn't cause any issues?
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  8. #8  
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    Metabones, never had an issue with mine.
    Cheers
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  9. #9  
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    I've found a commlite ef to mft than even has a lens chip, for €20 and it works just fine now. My advice, don't waste money on chinese Fotga adaptors for BM or if you do, be ready to have some issues. They prob work fine with GH's or other stuff, but not BM.
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