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Alexa Mini for HD deliverable (1 reply and 3 comments)

Rod
1 month ago
Rod 1 month ago

Hello Everybody,

I will be starting a small feature in a few weeks, we will be using the Alexa Mini on this project and we will deliver an HD Project (1:85) . I was thinking of oversampling (in Prores 4444). Could you help me out making up my mind on the different options that The Mini offers (4:3 2.8K or 3.2K; 4K(upscale 3.2K) etc ...)and weigh in the advantages they would gave me (sensor coverage, reframe ...)?

Thanks in advance

Camera Alexa Mini (Prores 4444)

Lens Cooke S4/i (18/24/32/50/75/100)

PS: Thank you Roger, James and everybody for making this forum such a great source of informations and inspirations.

dmullenasc
1 month ago
dmullenasc 1 month ago

Keep in mind that if you record 16:9 HD ProRes, you are already oversampling internally, the camera is using a 2880 x 1620 pixel area of the sensor and downsampling it to 1920 x 1080.

So the question is more whether it is worth recording a larger file like 3.2K 16:9 ProRes (3168 x 1778 pixels) and doing the downsampling to 1920 x 1080 later in post.

I think for an HD finish, the quality is already great just in normal shooting mode using the 2880 x 1620 area of the sensor but there are advantages to recording 3.2K 16:9:  one, if you have to do any vfx work, it would help to have a greater resolution to work with in case any resizing is necessary; two, the editor may need to occasionally crop & resize; three, some shots might need stabilization, which would causing some cropping; and four, a 3.2K recording would be better if ever a 3.8K UHD or a 4K DCP is ever needed.

The only disadvantage to using 3.2K is not only the greater storage requirements, plus maybe some higher frame rates might not be available, but also some of your wider Cooke S4 lenses might not cover the 3.2K sensor area.

 

Rod
1 month ago

Thanks David,
I did not know about the internal downsampling for HD, Arri really know what they are doing (2.8x0.7:1.96-HD) . Indeed my main reason for oversampling is for slight resizing options and stabilization. I agree with you, I do fear that the Cooke S4 will vignette on the wider ones (annoying especially for the 24mm, I don't plan on using the 18mm much)
what is your take on the 4:3 2.8K recording format (1:85) ?
the Cooke S4 will for sure cover the sensor on this settings.

dmullenasc
1 month ago

Again, if you record 2.8K for a 1080P finish, you are basically saving the downsampling for post rather than doing it in camera, which is mainly useful if you will have to crop & resize anything. If you are framing for 1.78 or 1.85, there's not much reason to record 4:3 unless you might need that vertical picture information for vfx work or stabilization. I think the only thing to consider is dailies, how to get them cropped and downsampled while making sure the final conform session goes back to the 2.8K originals, and to make sure the editor goes back to the 2.8K originals for any resizing or stabilization work.

Rod
1 month ago

Thanks.

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