2x Anamorphic on ALEXA 35: Open Gate vs. 6:5 Mode

[PSil001]

Hey everyone,

I was reading the August 2023 issue of ASC Magazine and came across this passage:

“There’s a misconception that 4:3 is the correct mode for anamorphic lenses. It isn’t. 4:3 is a 1.33:1 aspect ratio. If you use a 2x anamorphic lens, the result is a 2.66:1 image, which doesn’t fall into any standard delivery format. The actual specification for traditional 2x anamorphic is 6:5, which is a 1.2 aspect ration. So using a 2x anamorphic lens in 6:5 mode results in a 2.4:1 image (1.2 x 2 = 2.4). On the ALEXA 35, 6:5 mode crops the active sensor area to 3328 x 2790, which when unsqueezed becomes a 6656 x 2790 (2.39:1) image.”

This got me thinking. I always assumed that using Open Gate 4.6K on the ALEXA 35 would be the best option for anamorphic, since you’re using the full sensor. What’s the actual final resolution when using 4.6 Open Gate with a 2x anamorphic lens compared to shooting in 6:5 mode?

Is there any significant advantage in using Open Gate, or is 6:5 the preferred approach for a reason?

Thanks!

[Andreas Berkl]

Dear PSil001,

in our opinion this is a more a matter of data rates than resolution. In some cases the illumination circle of the lens may be relevant as well.

In Open Gate (https://tools.arri.com/flt/index.html?s ... G_4.6K_2.0) you have a resolution of 3776 x 3164 px with some horizontal "safety".

In 3.3K 6:5 (https://tools.arri.com/flt/index.html?s ... 5_3.3K_2.0) the resolution of 3328 x 2790 px is a bit less with no "safety".

So in the end it is a question of maximum resolution vs. data rates/lenses.

Hope this helps!

[PSil001]

Thanks! I noticed the Lens illumination tool on the ALEXA 35 includes anamorphic desqueeze option, but other ARRI cameras don’t seem to have that option. Is there any plan to implement this feature across the other models too?

[Andreas Berkl]

Dear PSil001,

this feature is currently only available for ALEXA 35. We will consider adding this for other cameras with the next bigger release.

Best regards,
Andreas Berkl