ARRI News September 2009 - ARRI Media

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28 Digital Intermediate Systems Singleflash vs. ARRISCAN LED + CMoS technology = highest dynamic range Doubleflash The ARRISCAN utilises a unique high power LED illumination system that allows for very accurate and repeatable exposure of the film. The possibility of upgrading an ARRISCAN 2k with the Doubleflash option provides a good reason for having a closer look at this clever piece of ARRI technology. Singleflash Doubleflash Film Stock: Kodak 5219 Vision 3 500 T Within the ARRISCAN, high power LEDs for red, green, blue and infrared expose the image one color after another for a real RGB image with the full (monochrome) 3k or 6k sensor resolution; meanwhile the copper heat dissipation module with active electrical (Peltier) cooling keeps the LEDs at a controlled temperature of 25°C for proper color reproduction. In combination with the ARRI-designed CMOS sensor, which can be overexposed, all ARRI- SCANs are capable of double flashing the film being scanned (though this is an optional extra for the ARRISCAN 2k). For film scanning, the image sensor needs to capture the whole dynamic range of the source material. The ARRISCAN calibrates its LEDs to avoid overexposing the sensor (clipping) at the least dense part of the film (usually the base: d min = 0). The higher the density of the film material, the less light can travel through the emulsion and reach the sensor. For a normal camera negative the highlights will have a maximum density of about 1.8, so these parts of the image will only let through roughly 1/60 of the light compared to the base. Every imaging device is susceptible to noise. The less light that reaches the sensor, the worse the signal-to-noise ratio becomes, no matter brightness 22750 22500 22250 22000 21750 21500 21250 21000 20750 20500 20250 20000 19750 19500 19250 19000 18750 18500 18250 18000 17750 17500 17250 17000 16750 16500 16250 16000 15750 15500 2.5 5 7.5 10 time (ms) After the first exposure and the sensor readout, the LED illumination produces a second flash with 10x the energy. how good the image sensor is; this is why ARRI introduced the Doubleflash technology. It is similar to HDR (high dynamic range) still photography in that it adds a second exposure, with ten times the light energy, to the first ‘standard’ scan. This second scan will be ten-times overexposed so that all image content that is below d = 1 is lost in clipping, but the maximum density on the film will expose the sensor to ten times more light than in the normal scan. A final blending of the two scans results in a much better signalto-noise ratio in the high densities than any normal scan technologies.
The effects of the Doubleflash technology on a colour wedge exposed with an ARRILASER In the lower and middle densities, the two xprofiles are exactly the same. In the higher densities, the average code values are still the same between Singleflash and Doubleflash (same linearity and color reproduction) but the Singleflash scan will show higher noise levels than the Doubleflash scan. x-profile ARRILASER color wedge, doubleflash scan x-profile ARRILASER color wedge, singleflash scan What does that mean for scanning? • The colour reproduction is exactly the same between Singleflash and Doubleflash. • The Doubleflash scan takes about twice the time of the Singleflash scan. • The noise level differences between Singleflash and Doubleflash only become visible in densities above 1.6 – 1.8. For a normal camera negative, the visible effects of this technology are minimal. Only the very bright / burnt-out highlights are of sufficient density on the film to show any difference between Singleflash and Doubleflash. • Print film has a much higher dynamic range of up to d -d = 4. This is min max a big issue for all film digitizing equipment using only one exposure. The superior quality of Doubleflash becomes more visible when dealing Digital Intermediate Systems First and second exposure are combined into high dynamic range scan of difficult overexposed material. with higher densities. With Doubleflash print film scanning results on the ARRISCAN are a lot cleaner than Singleflash scans or scans made with traditional equipment. • When film is overexposed, most of the image information is located in the high densities of the negative. In the grading process the image brightness has to be pulled down dramatically to bring back this information from the highlights. This results in a visible difference in noise level between Singleflash and Doubleflash. • Maximum densities measured on black & white film stocks can be higher than on color negative film. Therefore this film stock also benefits from Doubleflash scanning. 29
Page 1 and 2: 09/2009 A NEW DIGITAL CAMERA SYSTEM
Page 3 and 4: Dear Friends and Colleagues Dr. Mar
Page 5 and 6: Camera System Product code name: k
Page 7 and 8: The ARRI Digital Camera System > >
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Page 27: ARRICUBE Creator Package about why
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Page 39 and 40: Workshop for distributors at ARRI L
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