Thread: BMMCC + Sigma 17-50 2.8 EF aperture issues.

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  1. #1 BMMCC + Sigma 17-50 2.8 EF aperture issues. 
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    Hey guys,

    I've just gotten the Sigma 17-50 2.8 EF and put it on the bmpcc speed booster, OIS works great, image is really quite nice but a small annoying problem seems to be is that the speedbooster thinks its not a constant aperture lens. I can assure you it is, the image does not darken or lighten but as I zoom toward 50mm the aperture changes from 1.7 through to 3.2 as if it's losing light, it isn't.

    I'm running the latest firmware for the speedbooster 3.0, I've tried toggling some settings about auto aperture calculation in the metabones app but it's still changing which makes it a real pain for me to judge the lenses sweet spots and my depth.

    Was wondering if anyone knew a trick that I was missing? Otherwise I've contacted metabones support, hopefully they write back.

    Cheers.
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  2. #2  
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    That's really odd. I've used this exact combination for over a year now with no problems. I am rarely wide open but I feel like I would have noticed this if it were doing it on my setup. Will test and confirm tomorrow morning.
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  3. #3  
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    Tested on a canon dslr and it stays at 2.8 f stop throughout the zoom range without problem. mmmm wonder why it's doing it on the bmmcc.
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  4. #4  
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    Quote Originally Posted by GeranSimpson View Post
    That's really odd. I've used this exact combination for over a year now with no problems. I am rarely wide open but I feel like I would have noticed this if it were doing it on my setup. Will test and confirm tomorrow morning.
    Thanks for that!

    I also have the older sigma 10-20 which has a focus ring that never stops spinning, I noticed this sigma 17-50 2.8 has hard stops. Just wondering if yours also has hard stops?
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  5. #5  
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    Quote Originally Posted by Ryanite View Post
    Thanks for that!

    I also have the older sigma 10-20 which has a focus ring that never stops spinning, I noticed this sigma 17-50 2.8 has hard stops. Just wondering if yours also has hard stops?
    So I tested my lens and the aperture remained constant throughout. Yes the Sigma 17-50 has hard stops. I would test to see if other zooms remain constant as you zoom in. Could be the lens messing up, it's not the best out there.
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  6. #6  
    Hey, if you haven't found a solution yet, I was having similar issue with the Tokina 28-70 2.6-2.8. I solved it by holding down the jog dial as I turned on the camera and that seemed to fix it. (I might have also kept it held as I attached the lens, but I don't remember exactly! I would have a play around with holding down the jog dial.

    Hope this helps!

    EDIT: its worth noting I was using the XL with the GH5... but hopefully the same should apply!
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  7. #7  
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    Thanks for the test Geran, do you recall having to do what Jordan is mentioning to get it working initially?

    I saw that some of the adaptors have green and advanced modes but wasn't sure that the bmpcc adpator had that function. I'll have a play and see if I can get it going.
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  8. #8  
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    Really frustrating, I've only got a 10-20 sigma but that one isn't constant aperture so it wont help. But I have tried the 17-50 on my brothers canon dslr and it stays constant just fine.

    I held down the jogger when turning on the camera and when putting the lens on but it just get's worse really. it instead reads it's minimum aperture as 3.2 (instead of 1.7) but STILL counts up 3 stops through the zoom range. In this mode I can't lower the aperture below "3.2" I believe it is actually it's lowest 1.7 aperture but just reading incorrectly.

    Really has me stumped.

    edit - unbolted and resat the speedbooster but still nothing. I'm not sure if it's on the lens end or the speedboosters end. I might have to go out to a camera store and see if they'll let me try a display 17-50.

    I'll keep trying, hopefully I've done it wrong. This is listed under the advanced modes features but im not sure it applies to the pocket booster "A variable aperture lens would mimick a constant aperture lens using iris movement. For example, if an F/4-5.6 lens is set to f/8 at its widest zoom position, the aperture remains at f/8 at any zoom position, but the iris opens up as you zoom toward the tele end." You'd think that'd fix my issue even though it's not actually a variable aperture lens it sure is acting like one.
    Last edited by Ryanite; 06-19-2018 at 07:56 PM.
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