Recently Decode have been busy in the test room exploring all things technical. A long-form project has required us to carry out some tests of Arri Amira Latitude and also a comparison of filters, so we thought we’d share the results with you.
Our Arri Amira exposure latitude test was designed to evaluate the noise levels at the native ISO of 800. The sensor was rated at the base ISO of 800, white balanced to 3200 Kelvin and shot at 25 fps with 180-degree shutter.
The test was shot in ProRes 4444HQ 1920 x 1080 in ARRI Log C. This test evaluates information retained in Log C, then in comparison to an ARRI Rec 702 LUT applied in DaVinci Resolve. Secondly, we tested how much information could be reclaimed from the under and over exposed Log C footage back to normal exposure value.
The lens used was a Zeiss CP.2 85mm at T/5.6. The under exposure was achieved with Tiffen Neutral Density filters from 0.3 to 1.2. Over exposure was achieved by opening the iris at 1-stop intervals. 4-stops over exposure was achieved by moving the key and back light closer to increase exposure. Key and fill was balanced to a 2:1 ratio. Lit by a 2K Blonde open face book light through 216 diffusion, with a three quarter backlight from a 650w Fresnel bounced into a poly-board. Exposure was determined with a Minolta handheld light meter (the camera’s inbuilt waveform and false colour exposure tools were not used).
Under exposure held good detail, only starting to exhibit noise when the exposure increased from -2 stops to normal exposure. The Amira sensor demonstrated a very filmic curve at three 3-stops under exposure, dropping off steeply thereafter where we found we had reached the limit of what amount of detail could be recovered.
Over exposure demonstrated the Amira’s ability to retain usable highlight information. Even at 4-stops over exposed the image could be pulled down to average exposure level and still be clean and detailed.
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