(NB: These videos are 1080p. They should be viewed with full screen selected on a monitor big enough to view full HD)
This is a simple comparison of the final resolution of an image created with a 2 x anamorphic lens on an Arri Alexa and a Red Epic. The reason for this test is that the Epic captures a much higher resolution image than the Alexa, but how do they compare once they are both resized and rendered at 1080p, the usual delivery standard for something shot for TV. I hasten to add this is not a worthy test for something intended for projection.
The Epic 5K sensor captures an image size of 3226 x 2700 pixels. This is full height and cropped left and right to an academy ration as covered by the lens. The 16×9 chip does not cover the full height of the lens, but it does cover slightly more than the Alexa.
The Alexa 1920×1080 sensor (shooting to cards, not 2K Arri Raw) captures an image size of 1290 x 1080. The Alexa’s sensor is physically slightly smaller than the Epic’s, so to maintain the same angle of view as film the focal length of the lens would increase by a factor of 1.33 on the Alexa and 1.22 on the Epic.
All this equates to an image area 44% smaller than film on the Alexa and 33% smaller on the Epic. So on paper it seems to be all about the Epic…however that’s just numbers…
The Alexa image was captured to SxS card ProRes4444 in LogC at 25fps, then resized to 1920×1080 and processed in After Effect with a Log to Lin conversion and a tiny tweak to the colour balance.
The Epic image was captured in anamorphic mode with a 3:1 compression at 25fps, then resized to 1920×1080 and processed out through Red Cine X converting to REDcolor2 and REDgamma2 with a tiny tweak to the colour balance.
The same lens was used on both cameras. A Panavision 35mm USG at T5.6.
The most obvious thing is the size of the images. The Epic’s larger sensor gives a wider angle of view; a definite advantage. The difference in resolution is also apparent with the image from the Epic appearing slightly sharper than the Alexa, but only slightly; not the massive difference you might expect from the numbers.
So in conclusion the Epic does seems to win out but only just. If you prefer the Alexa as a camera then there is no reason not to shoot anamorphic on it, although the logistics of de-squeezing the image on set is much easier with the Epic. When Arri release the Alexa studio with it’s 4:3 full size chip covering 100% of a 2 x Anamorphic lens we should have the ultimate digital anamorphic camera.
I have since had a chance to look at these tests in a grading suite with a projector, and as far as resolution or the sharpness of the image is concerned there is very little to separate them. I should note that there seemed to be some color issues with the Alexa image, but it seems confined to this test and i have not seen this in any other Alexa footage. Arri have also update the Alexa’s firmware and it can now de-squeeze the image.
Thanks to Pat Wintersgill at Creativity Media.
Thanks to Trevor Henen for his excellent assistance, and to Tony and Adam at Panavision UK.