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Does Arri Amira/Alex crop like Red???

Arri Amira Arri Alexa Red Crop

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#1 David Yao

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Posted 28 November 2015 - 02:46 AM

Hello my fellow cinematographers and filmmakers! 

 

I got a question to be clarified ASAP since I'm going on a shoot and in need of the answer =)

I understand that Red camera has this issue where the crop factor is different as I change shooting with 4K to 2K. The crop will go from a APS-C size sensor area to a super 16 size sensor area. The camera is only using a certain part of the sensor as it records the set resolution. So the field of view of a 25mm on at 4K will be similar to that is of a super 35 but once it's changed to 2K then the crop makes the lens into a 80mm equivalent (math may not be exact, but you get the point). It’s troubling since the lenses will not have the same effect as different resolution is used. So I’m just wondering if Arri Amira/Alex has the same issue? Is the total area of the sensor (super 35 equivalent) going to be used as I change from shooting with 4K to 2K and 1080p? Does it also have this crop problem as Red? Simply put, if I use a 25mm on Amira shooting at 4K and then I change the resolution to 2K, then field of view of both should be exactly the same?

 

Thanks so much for taking the time to answer this!

David Yao

 

 


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#2 David Mullen ASC

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Posted 28 November 2015 - 03:11 AM

There's no cropping of the sensor in the Amira from 4K to 2K... because the camera does not have a 4K sensor.

 

The whole Amira sensor is 3414 x 2198 pixels total including look-around area.

 

In 4K UHD mode, you use a 3200 x 1800 pixel area and this gets up-sampled to 3840 x 2160 pixels (UHD) in the ProRes recording.  

 

In HD mode, you use a 2880 x 1620 pixel area, which gets down-sampled to 1920 x 1080 pixels for ProRes recording.  

 

In 2K mode, you use a 2868 x 1612 pixel area which gets down-sampled to 2048 x 1152 pixels for ProRes recording.

 

So all the formats that get recorded use a similar sized area of the sensor. The 2880 pixel area of the sensor is 23.76mm wide, similar to Super-35.  So if you switch from UHD to 2K, you are switching from using 3200 pixels across to 2868 pixels across.  That's only a 1.115 crop factor -- your 25mm lens in UHD mode will behave like you switched to a 28mm lens in 2K mode in terms of field of view, or to be more accurate, your 25mm lens will have a slightly wider view in UHD mode than in 2K mode.

 

The Red camera only records raw, so there is no up or down-sampling possible in-camera, it is very hard to have a 4K raw signal and shrink it to 2K while staying in raw, so when you go from 4K to 2K in the Red camera, it has to do that by cropping the sensor from 4K to 2K.  Cameras that use a 4K sensor area but record it as 2K usually are converting the 4K raw signal to RGB in order to then down-sample to a smaller file size.


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#3 Robin R Probyn

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Posted 28 November 2015 - 07:43 AM

Do you think that will be problem for Arri in the future,if/when everything goes REC 2020.. 4K.. UHD.. and their camera,s are not "real" 4K.. or they will come out with a true 4K sensor..?

 

I mean I dont think anyone is complaining about the picture so far ! ..


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#4 David Mullen ASC

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Posted 28 November 2015 - 11:29 AM

I'm sure it will become more and more of a problem over time -- already studios like Netflix which demand 4K origination won't approve of the Alexa or Amira for their in-house shows.  It's somewhat of an arbitrary line, because if you are shooting uncompressed Arriraw in Open Gate mode on the Alexa, you are talking about uncompressed 3.4K, which can be sharper and more detailed than some other cameras' 4K compressed codec recordings (and Netflix does accept UHD, 3840 pixels, so it seems hair-splitty not to accept 3414 pixels.)  On the other hand, there's a reason for standards and if it gets Hollywood to finally start budgeting for 4K post on all their projects, then it's a good thing in the long run.

 

Arri is working on a 4K or 5K 35mm-sensor Alexa, believe me, but they don't want to release a new camera where you don't get the same wide dynamic range and sensitivity of their current 3.4K sensor. I also think (I'm guessing here) that they probably don't want to upset all the buyers of their current cameras by releasing a new 4K camera until people feel they have gotten a return on their investment.


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#5 Robin R Probyn

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Posted 06 December 2015 - 08:42 PM

Hi Dave

 

Sorry just saw this..   even at my level of shooting 4K or more UHD is coming in now.. sometimes just for re framing options /future proofing.. Nice that Arri might be protecting their customers before releasing a new camera.. I guess they didnt get that idea from Sony :).. 


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#6 rob spence

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Posted 07 December 2015 - 09:17 AM

Regarding the Netflix 4k origination issue...how would a super 16 originated movie get onto the Netflis platform. (Such as Black Swan, Wrestler and Suffragette etc). Would they pass if the neg was scanned in 4K?


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#7 Stuart Brereton

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Posted 07 December 2015 - 10:40 AM

Regarding the Netflix 4k origination issue...how would a super 16 originated movie get onto the Netflis platform. (Such as Black Swan, Wrestler and Suffragette etc). Would they pass if the neg was scanned in 4K?

The 4K origination rule applies only to material they create, not to programming which is bought in.


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#8 rob spence

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Posted 07 December 2015 - 10:47 AM

Hi Stuart, thanks for the answer...will that mean that film origination ( for netflix originated content ) is possible or not?


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#9 David Mullen ASC

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Posted 07 December 2015 - 11:56 AM

I don't think anyone has tested film yet for Netflix original content, but I'm sure they would probably accept 35mm that went through a 4K D.I.


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#10 cole t parzenn

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Posted 07 December 2015 - 02:44 PM

According to IMDB, "Orange Is the New Black" is 1080p Alexa. It looks like the Alexa to me, FWIW.


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#11 Kenny N Suleimanagich

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Posted 07 December 2015 - 03:41 PM

I don't think anyone has tested film yet for Netflix original content, but I'm sure they would probably accept 35mm that went through a 4K D.I.

"Hand of God" shoots 35mm for Amazon – per this article.  Though I am not sure that Amazon requires 4K origination. 


Edited by Kenny N Suleimanagich, 07 December 2015 - 03:41 PM.

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#12 David Mullen ASC

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Posted 07 December 2015 - 03:51 PM

According to IMDB, "Orange Is the New Black" is 1080p Alexa. It looks like the Alexa to me, FWIW.


The show switched to the Panasonic Varicam 4K camera this year.
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#13 cole t parzenn

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Posted 07 December 2015 - 04:50 PM

This year, meaning the most recent season or the upcoming season?


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#14 David Mullen ASC

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Posted 07 December 2015 - 05:19 PM

The upcoming season.


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