Shooting and Matchmoving Anamorphic Plates

I'd like to talk with my colleagues in the visual effects and cinematographer fields about the pluses and minuses of shooting visual effects with anamorphic lenses, as opposed to spherical lenses.

From the development of Cinemascope in 1953, through the later widespread use of Panavision lenses, anamorphic has long been the preferred 35mm filming format of big feature films. But that started to change when Silverado was shot in Super 35 spherical in 1985. And then director James Cameron pushed the industry back into the common use of Super 35 spherical, with True Lies andTitanic, as well as with the Ron Howard Super 35 production of Apollo 13.

The reason that Cameron championed Super 35 spherical is that anamorphic lenses have many problematic aberrations, which make them difficult to use for visual effects, That's why the original Star Wars 4 visual effects were shot on spherical Vistavision, since anamorphic photography is quite counter productive for vfx.

So life was good for a while, in the vfx heaven of spherical 35mm photography.

But since 2010, anamorphic has been making a resurgence, especially sinceJohn Carter of Mars. And in the digital age of Alexa and Red high end production cameras, anamorphic photography has seen a rebirth.

And this resurgence is perhaps not a good thing.

This is because, from a Matchmove perspective, anamorphic sucks.

We have been working closely with 3D Equalizer for the last two years, who have developed sophisticated tools to handle the asymmetrical lens breathing of anamorphic lenses. We know that spherical lenses exhibit a slight focal length zooming during focusing, which is commonly called "lens breathing". It is easy for us to solve for animated symmetrical lens breathing in spherical. But anamorphic lenses breathe differently in the vertical and horizontal. So this asymmetrical anamorphic lens breathing is quite a headache to track, even with the excellent new anamorphic lens distortion models from 3D Equalizer. It is common for a spherical shot to be tracked in half the time as an identical anamorphic plate shot.

I recently was a Matchmove supervisor on a major Hollywood action film, which was shot with Alexa XT anamorphic, Alexa XT spherical and Alexa 65 spherical.

It is non-trivial for an visual effects professional or audience member to discern the difference between Alexa anamorphic and Alexa spherical. But anamorphic is quite painful to track, so what is the point of using that format, instead of tried and true spherical? Of course anamorphic has theoretical advantages, such as higher pixel count, weird lens flares, softer images, heavy barrel distortion and distinctive asymmetrical rack focuses.

Many current Alexa anamorphic productions are actually using Panavision C lenses, which are from the 1960s. These lenses are not very sharp, but they are much more compact than more "modern" anamorphic lenses, which are often bulky and heavy.

As a side note, the Alexa 65 footage on this same show was difficult to track, since it was almost all underexposed and quite grainy. We had many shots on the exact same sound stage set and because it was lit for T/2.8 and the larger format Alexa 65 lenses only open up to T/4. So even though the Alexa 65 is a 6K camera, an underexposed 6k image looks much worse and is more difficult to track than a plain vanilla Alexa XT spherical properly exposed.

Since currently capture can be 6k and exhibition in theaters is 4k max, I think a director wishing to have an Anamorphic Release should capture at the highest Spherical resolution that is practical given the time, budget and local, 6k or higher if possible. Then after all VFX work is complete, all the Anamorphic artifacts and quirks can be applied digitally in post like a DI session. Gate size must be chosen to be sure through post there is always enough image captured to cover for the needs of anamorphosizing in post. Since Anamorphic is a less perfect result, we can digitally degrade any footage to have the anamorphic signature attributes, but let's capture the sharpest, best exposed, highest resolution flat image possible, first.

So we'd like to open this subject up for discussion. I want to be completely clear that in Matchmove departments around the globe, when anamorphic plates are ingested into a Matchmove department to track, there is a collective groan among the staff.

Format x pixels y pixels pixel count aspect ratio pixel count, cropped to 2.40:1
Alexa anamorphic 4:3 2880 2160 6,220,800 2.6666666667 5,598,720
Alexa spherical 16:9 2880 1620 4,665,600 1.7777777778 3,456,000
Alexa Open Gate spherical 3414 2198 7,503,972 1.5532302093 4,856,415
Alexa 65 Open Gate 6560 3100 20,336,000 2.1161290323 18,302,400
UHD 4k 3840 2160 8,294,400 1.7777777778 6,144,000

-Michael Karp, SOC

Notes:

Arri ProRes is intended as an Alexa upscale to 4k UD format. Details here.
http://www.linkgroup.com.tr/Content/files/ARRI_ProRes_3.2k.pdf
 or mirrored at:
http://michaelkarp.net/ARRI_ProRes_3.2k.pdf

It would seem from this chart that if you shoot Alexa Open Gate spherical, the pixel count for 2.40:1 is almost as high as anamorphic (4,8 million pixels, versus 5.6 million pixels).
Plus the spherical lenses are much sharper.

It probably is not okay to shoot Open Gate anamorphic, the lenses won't cover the larger sensor size.

A Digital Finish for Seabiscuit
http://www.theasc.com/magazine/aug03/sub2/

Sensor size spreadsheet:
http://michaelkarp.net/Alexa_anamorphic_vs_spherical_pixel_count_2.40AR.xls