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Arri Sr3 HS - Adjustment Normal 16 /Super 16

arri super16 lensadjustment format aspectratio

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#1 Walter Stoehr

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Posted 14 July 2017 - 04:15 AM

Hello,

 

I've bought a used Arri Sr3 Highspeed. It is adjusted to super 16. I haven't used it in a while and I have an anamorphic shoot coming up where I will be using 2x anamorphics. I want to shoot in Normal16 to get the 2,66:1 aspect ratio. Do I have to get through the adjustment of changing the camera's lens alignment, the opening in the universal film gate and the viewfinder alignment in order to convert it to normal16? I lack the tools and the experience to do so. I get that I definately need to do this when adjusting from normal 16 to super 16, but isn't it sufficient to just change the Fibre Optic Viewing Screen in my case? In post I would just have to crop the sides because the Super16 just uses a larger portion of the negative. I won't lose any resolution by going down this road in comparison to adjusting all the mentioned parts of the camera and just have the additional portion of the super 16 frame covered and unexposed in normal16 "mode", right?

 

Thank you so much for the answers!

Best

Walter


Edited by Walter Stoehr, 14 July 2017 - 04:17 AM.

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#2 aapo lettinen

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Posted 14 July 2017 - 05:42 AM

If you have a gg that has s16 centered 1.37 or 1.33 markings, then it would work fine if just changing the screen. Otherwise the optical axis would be off centered which would make weird off center flares and parallax errors when tilting and panning
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#3 Walter Stoehr

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Posted 14 July 2017 - 08:03 AM

If you have a gg that has s16 centered 1.37 or 1.33 markings, then it would work fine if just changing the screen. Otherwise the optical axis would be off centered which would make weird off center flares and parallax errors when tilting and panning

Thanks for the reply. I am not exactly sure what you mean. I have two ground glasses. One super16 and one that has 1.37 aspect ratio. When I insert the N16 one, am I ready to go? I attached photos of the 1.37 TV one. Thanks!

 

https://www.dropbox.... N16_2.jpg?dl=0

https://www.dropbox....ss N16.jpg?dl=0


Edited by Walter Stoehr, 14 July 2017 - 08:06 AM.

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#4 aapo lettinen

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Posted 14 July 2017 - 10:48 AM

If using a n16 centered ground glass in a s16 centered camera, your optical axis would be slightly to the right from the frame center which causes some problems though you could definitely film with that kind of setup. If you dont have a s16 ground glass which has 1.37 or 1.33 markongs i would recommend switching the pl mount to n16 position to avoid problems. .
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#5 Walter Stoehr

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Posted 14 July 2017 - 11:23 AM

If using a n16 centered ground glass in a s16 centered camera, your optical axis would be slightly to the right from the frame center which causes some problems though you could definitely film with that kind of setup. If you dont have a s16 ground glass which has 1.37 or 1.33 markongs i would recommend switching the pl mount to n16 position to avoid problems. .

Ah, I see. If I had a GG like in that picture on the top, I'd be ok and could shoot S16 and crop the sides without having problems with the optical axis, right? http://i.imgur.com/xArDAfE.png?1

I would then need to crop the sides in post to get the 2,66:1 ratio with the anamorphics. The N16 ground glass (+adjustment) does not give me more resolution/information than the version I just described, correct? When I'd find such a groundglass with 1.33/1.37 markings I wouldn't have to change the PL mount to N16/S16 position ever again?

Thanks.


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#6 Dom Jaeger

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Posted 14 July 2017 - 06:59 PM

Your issue is really just about framing while you shoot, the full camera aperture will be exposed whether you are centred on N16 or S16, but ideally you want to extract your framed aspect ratio from the optical centre. Traditionally that meant a 1.2:1 image, but if you want to go wider you can extract a 1.33:1 frame to get 2.66:1 unsqueezed.

One trick we often did was to use thin strips of sticky tape to mark a new frame line on an SR ground glass (on the recessed side not the flush side that is where the gg seats). So you could do that with your S16 gg, to give you some guide for framing (remembering you may not get the full height with a S16 gg if the marked aspect ratio is wider than the aperture). It's a bit fiddly, and helps to have a scalpel, tweezers, a magnifying loupe and vernier calipers to get it roughly right. You can shoot a framing chart to give you or the post facility a guide to where you've framed for extraction.

But if you have a 1.33 ground glass for N16 it's pretty easy to swap over, just carefully undo the mount screws and rotate the mount 180 degrees, taking care not to fold or misalign the shims underneath. The locating screw at top right of the PL mount will also need to be shifted across, and maybe the bridgeplate as well. Probably worth checking that your lenses still line up afterwards if you'll be relying on focus marks.

You will be looking at a squeezed image in the viewfinder, which is not ideal, but people get used to it I've heard.
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#7 Walter Stoehr

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Posted 15 July 2017 - 08:31 AM

But if you have a 1.33 ground glass for N16 it's pretty easy to swap over, just carefully undo the mount screws and rotate the mount 180 degrees, taking care not to fold or misalign the shims underneath. The locating screw at top right of the PL mount will also need to be shifted across, and maybe the bridgeplate as well. Probably worth checking that your lenses still line up afterwards if you'll be relying on focus marks.

 

Alright, so I don't have to adjust the film gate on the mags or the viewfinder necissarily, right?


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#8 Dom Jaeger

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Posted 15 July 2017 - 02:57 PM

Alright, so I don't have to adjust the film gate on the mags or the viewfinder necissarily, right?


Right, no adjustment needed to those parts.
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