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.
Decodes camera filter test was carried out to compare the effects of popular Tiffen digital camera filtration: Black Pro Mist, Glimmer Glass and HDTV FX. We shot using the Arri Amira, Zeiss CP.2 lenses, and the following settings:
ProRes 4444HQ, 1920 x 1080, ARRI Rec 709, 3200 Kelvin, ISO 800, 25fps and 180 degree shutter angle.
– Tiffen Black Pro-Mist 1/8, 1/4, 1/2, 1, 2
– Tiffen Glimmerglass 1, 3, 4, 5 (2 was unavailable)
– Tiffen HD TV/FX 1/4, 1/2, 1, 2
In regards to lighting, key and fill were 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.
Black Pro-Mist filters offer a unique layering of contrast combined with a gauzy paint like halation. Even at its lowest density it delivers an effective increase in the halation which adds a pleasing depth of warmth, but is not visible to the skin tone values. These characteristics will become more apparent when you use densities of 1/4 and above. In the heavier densities, the spill is quite aggressive from the practical light, with the warm tone becoming more apparent.
Glimmerglass is a range of diffusion filters that produces a soft clean halation around practical and specular light sources, while keeping an apparent sharpness in the overall image. On close ups, the apparent sharpness and fine detail is kept as the effect of the filter lowers contrast while softly rolling into the shadow area. This low contrast effect moderately mutes bright colours. This makes the lower end of the glimmer glass diffusion range produce a non-destructive or invasive look. Even at heavier densities the filter never becomes overly powerful in its spread of halation.
The HDTV / FX filters produce a very inconspicuous effect on the images as it works on reducing both contrast and resolution. The contrast reduction constituent withholds flaring from practical or specular highlights. While the resolution element of the filter does not over glare the image keeping an apparent sharpness in all the important places. A good option for emulating slightly older style lenses when in fact using today’s super sharp optics.
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