On Open Gate

Simon Jori, a local Digital Imaging Technician, has shared with us his findings and thoughts on Arri’s new Open Gate. Thank you to Simon for sharing.
There is a little confusion as to the number of pixels in the Open Gate format as ARRI and the Alexa cameras internally use an active pixel area of 3414×2198 whereas the camera actually records 3424×2202 pixels. The reason for this is ARRI felt that these outer few rows and columns were not up to their standards and contained unwanted artifacting.
It is looking very likely that ARRI is going to put a stake in the ground and peg Open Gate as being at a resolution of 3414×2198. The “fix” to get the correct resolution only requires a center crop extraction out of the 3424×2202 to get to the “blessed” Open Gate resolution per ARRI.

Attached is a xml file with my 2.40:1 and 1.78:1 frame lines and some 25% masking (JORI_240_90_25.xml)

The frame lines are scaled in 10%, to clear lens vignetting and matte boxes, allow surround view to operator, and extra image area for VFX.
The 16×9 frame corners are centered.
The 2.40:1 frame lines are raised “half way” up towards the centered 16×9 frame. That is: one quarter – three quarters, toward common top.

Here’s the secret:

<camera>
<type>Alexa 3:2</type>
<sensor>3K</sensor>
<aspect>1.55</aspect>
<hres>3414</hres>
<vres>2198</vres>
</camera>

The attached OG_240_90.jpg file can be loaded into the camera as a frame grab and compared with the created framelines to confirm accuracy.
It is also valuable to Post and VFX as to frame line dimensions.

Cheers,
-Si

{click on the image to see or download the full image}

{Wordpress will not allow XML files or txt files so here is SImon’s XML file in pasted text}

<?xml version=”1.0″ encoding=”UTF-8″?>

<!– ARRI Alexa Frameline definition –>

<!– Generated by Simon Jori (Digital Imaging Tech) –>
<!– creation time: 2014-01-07 12:00:00 (user time) –>

<!– +++++++++++++++++++++++++++ –>
<!– basic format information    –>
<!– Open Gate Mode              –>
<!– Format A: 2.40:1 Raised     –>
<!– Format B: 1.78:1 (16:9)     –>
<!– Position: 2.40:1 raised 1/2 way towards 1.78:1 –>
<!– Marker: Format A: Small Dot –>
<!– Scale Formats: 90%          –>
<!– +++++++++++++++++++++++++++ –>

<framelines>
<camera>
<type>Alexa 3:2</type>
<sensor>3K</sensor>
<aspect>1.55</aspect>
<hres>3414</hres>
<vres>2198</vres>
</camera>
<!– surround view opacity  –>
<surround>
<opacity>0</opacity>
</surround>
<!– Format A upper dimming –>
<rect>
<left>0.00000</left>
<right>0.00000</right>
<top>0.00000</top>
<bottom>0.84220</bottom>
<border>
<width>0</width>
<color>user</color>
</border>
<fill>
<color>black</color>
<opacity>0.25</opacity>
</fill>
</rect>
<!– Format A lower dimming –>
<rect>
<left>0.00000</left>
<right>0.00000</right>
<top>0.74027</top>
<bottom>0.00000</bottom>
<border>
<width>0</width>
<color>user</color>
</border>
<fill>
<color>black</color>
<opacity>0.25</opacity>
</fill>
</rect>
<!– Format A left dimming –>
<rect>
<left>0.00000</left>
<right>0.95000</right>
<top>0.00000</top>
<bottom>0.00000</bottom>
<border>
<width>0</width>
<color>user</color>
</border>
<fill>
<color>black</color>
<opacity>0.25</opacity>
</fill>
</rect>
<!– Format A right dimming –>
<rect>
<left>0.95000</left>
<right>0.00000</right>
<top>0.00000</top>
<bottom>0.00000</bottom>
<border>
<width>0</width>
<color>user</color>
</border>
<fill>
<color>black</color>
<opacity>0.25</opacity>
</fill>
</rect>
<!– Format upper blackout to cover blinking purple line 0 –>
<rect>
<left>0.00000</left>
<right>0.00000</right>
<top>0.00000</top>
<bottom>0.99950</bottom>
<border>
<width>0</width>
<color>user</color>
</border>
<fill>
<color>black</color>
<opacity>1</opacity>
</fill>
</rect>
<!– Format A top line –>
<line>
<left>0.05000</left>
<right>0.05000</right>
<top>0.15780</top>
<width>4</width>
<color>white</color>
</line>
<!– Format A bottom line –>
<line>
<left>0.05000</left>
<right>0.05000</right>
<bottom>0.25973</bottom>
<width>4</width>
<color>white</color>
</line>
<!– Format A left line –>
<line>
<top>0.15780</top>
<bottom>0.25973</bottom>
<left>0.05000</left>
<width>4</width>
<color>white</color>
</line>
<!– Format A right line –>
<line>
<top>0.15780</top>
<bottom>0.25973</bottom>
<right>0.05000</right>
<width>4</width>
<color>white</color>
</line>
<!– Format B top lines –>
<line>
<left>0.05000</left>
<right>0.93300</right>
<top>0.10684</top>
<width>1</width>
<color>user</color>
</line>
<line>
<left>0.93300</left>
<right>0.05000</right>
<top>0.10684</top>
<width>1</width>
<color>user</color>
</line>
<!– Format B bottom lines –>
<line>
<left>0.05000</left>
<right>0.93300</right>
<bottom>0.10684</bottom>
<width>1</width>
<color>user</color>
</line>
<line>
<left>0.93300</left>
<right>0.05000</right>
<bottom>0.10684</bottom>
<width>1</width>
<color>user</color>
</line>
<!–Format B hash markers–>
<!– top left –>
<line>
<left>0.05000</left>
<top>0.10684</top>
<bottom>0.86768</bottom>
<width>1</width>
<color>user</color>
</line>
<!– top right –>
<line>
<right>0.05000</right>
<top>0.10684</top>
<bottom>0.86768</bottom>
<width>1</width>
<color>user</color>
</line>
<!– bottom left –>
<line>
<left>0.05000</left>
<bottom>0.10684</bottom>
<top>0.86768</top>
<width>1</width>
<color>user</color>
</line>
<!– bottom right –>
<line>
<right>0.05000</right>
<bottom>0.10684</bottom>
<top>0.86768</top>
<width>1</width>
<color>user</color>
</line>
<!– small center dot –>
<line>
<left>0.5</left>
<top>0.44765</top>
<bottom>0.54958</bottom>
<width>4</width>
<color>white</color>
</line>
</framelines>

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One thought on “On Open Gate

  1. Thanks for the read. Can’t say enough good things about Simon and his work addressing this issue during pre-pro!

    This is certainly a good thing to be aware of when working with any of Arri’s brand new cameras as a lot of them do this. However, these pixels that ARRI deem as “un-usable” will often be automatically cropped out in most software. On the job that Simon made this leader (shown above), our Colorfront OSD software was not automatically cropping those pixels out. Because the camera was so brand new, many software companies had not implemented the auto crop yet. Therefore we had to be very mindful of this when beginning production and on through post, considering by the time we hit post, most software was now automatically cropping this footage… Which means our meta data from the beginning of production for cropping would not automate into post perfectly considering today’s software would not include this auto crop within their math for any crop you dial in…!

    However with Open gate today, OSD, EXD, Nuke, Hiero, Baselight, Resolve, etc.. They will all now auto crop these bad pixels and its not something you need to be to concerned about.

    However recently we went through the same thing all over again with the Arri65 🙂

    Cheers,
    Jesse Korosi
    ________________

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