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Taping Arri SR for 16:9


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#1 Wiki Park

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Posted 19 July 2011 - 11:05 PM

I have marked an Arri 16s ground glass with masking tape before and would like to do the same thing with the Arri SR fiber optic plate. However, seeing that I am unable to examine what I am taping when I pull the fiber optic plate, would anyone have any suggestions as to how I can go about accurately marking the plate for 16:9? Would it be best to simply measure the plate once I have pulled it out of the camera? Any suggestions on this procedure will help me greatly. Thanks and all the best!
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#2 Dom Jaeger

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Posted 20 July 2011 - 11:31 PM

Hi Wiki,

it's not as simple as marking a 16S ground glass unfortunately, but the same principle applies. I'm assuming it's a Standard 16 ground glass.

In the past what I've done is cut 2 thin strips of contact adhesive, 1.5mm wide and 15mm long, and placed them along the top and bottom of the upper surface of the fibre screen. (The lower surface is where the frame seats in the camera, very important in maintaining the proper flange depth for focus, so you don't want to put anything on that side.)

On the upper surface the fibre screen is recessed, so the contact adhesive strips are placed inside the top and bottom edges of that recess. I fold the last 1mm of the strips, to make a handle to remove them if they need repositioning. The handles can be snipped off with scissors once the position is correct. The relative position of your 1.78 frame doesn't matter, it can be centered or top or bottom etc. I find centered easier to mark. For extraction you just need to shoot a frame leader showing how you've framed.

You need to fit the ground glass, check it through the viewfinder against a frame you've marked up, and reposition the strips if necessary. It can take a few goes, and some plastic tweezers and a magnifying loupe is helpful.

Chances are you have TV frame lines (1.33) which as an aspect ratio crops in a little at the sides compared to the 1.37 full gate aperture. If you use the inner 'TV safe action' frame you'll be losing too much area to cropping, it's only 8.4 mm wide. The outer 'TV transmitted' frame lines (actually just corners) are 9.35mm wide, so if you used that frame you'd want you're unmasked 16:9 area to be a little under 5.3 mm height. But the corner markings mean it can be hard to judge the exact edges of the frame, unless you use more strips to complete the side frame lines.

Perhaps simplest is to use the very outer frame line (surrounded by the grey area), which is the full aperture so you're using the maximum film width, but it will leave you no wriggle space on the sides. It's 10.3 mm wide, so your height then would need to be 5.8mm.

Good luck!
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#3 Wiki Park

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Posted 21 July 2011 - 02:21 AM

WOW, thank you always for your comprehensive advice! It is extremely helpful. I will try your method out. Thanks again!
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