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Shooting Open Gate


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#1 Eric Soto

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Posted 15 January 2018 - 03:12 PM

Hey everyone, what are the benefits of shooting open gate on a camera like the Alexa XT ?

 

Thanks.


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#2 Stuart Brereton

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Posted 15 January 2018 - 03:21 PM

Increased resolution.


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#3 Eric Soto

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Posted 15 January 2018 - 03:22 PM

Increased resolution.

 

What would be the reason not to always shoot open gate then ?


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#4 Stuart Brereton

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Posted 15 January 2018 - 04:09 PM

Shooting open gate can cause problems with certain lens's image circle not covering the entire sensor area.


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#5 Eric Soto

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Posted 15 January 2018 - 04:10 PM

Shooting open gate can cause problems with certain lens's image circle not covering the entire sensor area.

I see. ok. Thanks. 


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#6 David Mullen ASC

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Posted 15 January 2018 - 08:50 PM

Keep in mind that Open Gate is a 1.55 : 1 aspect ratio, so there is no advantage if you are shooting with anamorphic lenses, for example, or want a 4:3 image.  

 

Close to 3.4K Open Gate ARRIRAW is 3.2K ProRes on the Alexa.  Either would upsample to 3.8K UHD or 4K for a DCP well.


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#7 Eric Soto

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Posted 15 January 2018 - 09:03 PM

Keep in mind that Open Gate is a 1.55 : 1 aspect ratio, so there is no advantage if you are shooting with anamorphic lenses, for example, or want a 4:3 image.  

 

Close to 3.4K Open Gate ARRIRAW is 3.2K ProRes on the Alexa.  Either would upsample to 3.8K UHD or 4K for a DCP well.

 

I apologise if this may seem redundant for you, but could expand on why there would be no advantage to shooting on anamorphic lenses in Open Gate ? Would it be because the anamorphic lenses have a stretch of 2:1, and would therefore not use the full open gate resolution?


Edited by Eric Soto, 15 January 2018 - 09:10 PM.

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#8 David Mullen ASC

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Posted 15 January 2018 - 09:27 PM

If you are shooting with 2X anamorphic lenses for a final unsqueezed image with a 2.40 : 1 aspect ratio, that means you are using an area of the sensor that is 1.20 : 1 (6:5) with an image with a 2X optical horizontal squeeze.  So if you have a 4:3 Alexa and you switch to recording Open Gate, you are gaining more side information of the sensor but not really more height of the sensor.  You don't really need that extra info on the sides since you are going to end up cropping to a 1.20 : 1 area.

 

You can see here that Open Gate and 2.40 anamorphic share the same sensor height:

 

SUP_11_ALEXA-XT-Plus-M-Studio_Rec-Areas-


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#9 Eric Soto

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Posted 15 January 2018 - 09:39 PM

If you are shooting with 2X anamorphic lenses for a final unsqueezed image with a 2.40 : 1 aspect ratio, that means you are using an area of the sensor that is 1.20 : 1 (6:5) with an image with a 2X optical horizontal squeeze.  So if you have a 4:3 Alexa and you switch to recording Open Gate, you are gaining more side information of the sensor but not really more height of the sensor.  You don't really need that extra info on the sides since you are going to end up cropping to a 1.20 : 1 area.

 

You can see here that Open Gate and 2.40 anamorphic share the same sensor height:

 

SUP_11_ALEXA-XT-Plus-M-Studio_Rec-Areas-

 

Great. Thank you.


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#10 Eric Soto

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Posted 16 January 2018 - 12:10 PM

If you are shooting with 2X anamorphic lenses for a final unsqueezed image with a 2.40 : 1 aspect ratio, that means you are using an area of the sensor that is 1.20 : 1 (6:5) with an image with a 2X optical horizontal squeeze.  So if you have a 4:3 Alexa and you switch to recording Open Gate, you are gaining more side information of the sensor but not really more height of the sensor.  You don't really need that extra info on the sides since you are going to end up cropping to a 1.20 : 1 area.

 

You can see here that Open Gate and 2.40 anamorphic share the same sensor height:

 

 

 

So I looked this over and I fully understand what you mean now, but one question unrelated to open gate but to this page you sent. What is the difference between Arri 2.39 Flat and Arri 2.39 Scope 2x ? I thought that flat refers to 1.78- 1.85 ?

 

Thanks


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#11 Stuart Brereton

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Posted 16 January 2018 - 12:17 PM

Flat refers to shooting with spherical lenses, as opposed to anamorphic lenses. Flat 2.39:1 is derived by cropping the sensor to that aspect ratio. Scope 2.39:1 is anamorphic.


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#12 Eric Soto

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Posted 16 January 2018 - 12:21 PM

Flat refers to shooting with spherical lenses, as opposed to anamorphic lenses. Flat 2.39:1 is derived by cropping the sensor to that aspect ratio. Scope 2.39:1 is anamorphic

 

OK I see. Thank you.


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