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Omar Lopex

Arri SRII DIY Super 16 Conversion

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Does anyone have image grabs of frames that show the supposed streak that happens in the S16 space when the mirrors are not adjusted?

Image grabs that show the scratch marks in S16 space when the magazine is not modified?

I'm converting my SRII to Ultra-16 to avoid costs of Super-16 conversion, but want to double-check if I can't just go all the way and do the S16 conversion, then just crop around the streaked/scratched parts (if by chance they tend to happen only on corners?).

My camera has already been modified to use M42 mount 35mm lenses, so realigning the lens shouldn't be necessary, and I can frame by eye without a realigned viewfinder, so the only concern is scratches/streaks on the film.

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You can probably fix the shutter by extending it very slightly with a piece of plastic. I've seen many cameras that have done this. So that would solve the super 16 issue. Even if you forget about re-centering the lens or ground glass, just focus on increasing the aperture size and fixing the shutter, I think it would work fine. 

In terms of "scratching"  I mean the SR's have a super long gate, so that's a lot of film being squeezed between the pressure plate and the gate on those rails. I would never trust the side of the film to not be damaged. My XTR Prod tears up the area where the sprocket holes are, the SR's would do the same thing. The damage would happen anytime you're modifying the camera outside of it's normal 1.33:1 aspect ratio. So the benefit of making the camera ultra 16 or super 16 kinda goes out the window if those pieces of film are going to be damaged all the time. 

I personally wouldn't spend the money at converting. I'd just simply crop the top and bottom to the aspect ratio you want. Yes super 16 is nice, but it's a very small difference in image size, (1.33:1 vs 1.66:1) not the huge difference of lets say 3 perf and 2 perf 35mm. So it's a real toss up in my view. I shoot a lot of standard 16 and cropping to 1.75:1 for HD isn't a big deal. You wouldn't even notice really. 

This was all shot on an SRI standard 16: 

 

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10 hours ago, Omar Lopex said:

Does anyone have image grabs of frames that show the supposed streak that happens in the S16 space when the mirrors are not adjusted?

Image grabs that show the scratch marks in S16 space when the magazine is not modified?

I'm converting my SRII to Ultra-16 to avoid costs of Super-16 conversion, but want to double-check if I can't just go all the way and do the S16 conversion, then just crop around the streaked/scratched parts (if by chance they tend to happen only on corners?).

My camera has already been modified to use M42 mount 35mm lenses, so realigning the lens shouldn't be necessary, and I can frame by eye without a realigned viewfinder, so the only concern is scratches/streaks on the film.

Because the mirror/shutter edge lines up with the expanded edge of the S16 gate aperture, if you don't decrease the shutter angle from 180 to 172.8 degrees you will get smearing along the whole edge of the frame. If you crop it out you may as well not have converted to S16 in the first place. Many people glued a lightweight wedge to the mirror edge to do this, but it needs to be securely fixed and very accurately positioned so as not to scrape while spinning. Typically a job for a trained technician. 

The magazine conversion is less essential, though there is definitely a possibility that the expanded S16 area will get scratches, scuffs or simply bruising. Again, it affects the whole side of the frame where rollers, sprockets and guides will contact the newly expanded image area, so cropping just gets you back to N16.

If you don't re-centre the lens mount you probably won't notice anything drastic with 35mm format lenses except zooms will track off to one side. 

How are you modifying the gate? If it's not done very competently you will get scratches from burred edges. Don't just use a file for example.  If you expand into the area of the left vertical support rail you need to machine that rail down thinner all along its length so that the expanded picture area does not run along it. Google pictures of the narrow left rail on SR3 gates.

When I was working on Arriflexes, I would use a jig with a gauge to re-fit the gate so that the aperture lined up with the ground glass, and then use a depth gauge to check and adjust the flange depth to within 0.01mm. Everything on Arriflexes is adjustable, if you take them apart you can easily lose fine settings. 

Personally I think if you can't afford an already converted S16 SR2 , it's a waste of time trying to convert one on the cheap. A half-arsed conversion will turn what was a professional camera into little better than a quieter K3. 

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