Image Performance Enhancements in the C300 Mark II Abstract The original EOS C300 digital cine camcorder employed an innovative new 4K UHD Super 35mm CMOS image sensor developed by Canon [1]. The readout system dissected that 4K sampling into four parallel HD components. The summation of the two green components reduced aliasing that, in turn, supported a higher Luma MTF [2]. The new C300 Mark II preserves these basic strategies but within a totally new 4K CMOS image sensor design.
2.0 HDR Origination – New Super 35mm CMOS Image Sensor It has been almost four years since the original C300 was introduced to the worldwide marketplace. The novel CMOS image sensor specifically developed for that camera has served unusually well over those years – and continues to do so. But, Canon R&D never stops and a totally new generation CMOS Super 35mm image sensor is the heart of the stunning imagery of the C300 Mark II.
.0 Formulation of 2K or HD RGB 444 Video Components The image sensor parallel readout architecture breaks down the Bayer sampled 4K / UHD data into four parallel 2K / HD components as shown in Figure 2. Figure 2 Showing the unique component video signal processing in the C300 Mark II that formulates the 2K / HD RGB 4:4:4 video component set that is sent to the XF-AVC codec for recording A low noise analog column amplifier implements the ISO gain control when the scene Illuminance is very low.
6.0 Formulation of the YUV 422 Video Component Set The C300 Mark II can alternatively be switched to originate a Luma Y and two Chroma Cr and Cb 4:2:2 component set at a 10-bit depth and which can be selected to operate at all international picture capture rates up to 60 fps.
7.0 120 FPS Operation of 2K / HD When the C300 Mark II is originating in 2K or HD it can record picture capture rates from 1 fps up to a maximum of 120 fps progressive. To do this, however, the data rate of the video components emanating from the image sensor system must be constrained so that the processing and recording can retain a high integrity. The expedient to accomplish this curtailment of maximum data rate is to center crop the image sensor readout.
For this reason, the C300 Mark II also incorporates the ability to originate very high performance video in the standardized 4K / UHD formats – at frame rates of 23.98 / 24.00 / 25.0 / 29.97 fps progressive. Figure 5 Showing the video processing system to create the 4K / UHD YCbCr 4:2:2 video that is sent to the XF-AVC codec for recording 9.
Figure 6 New Canon Log2 Opto Electronic Transfer Function (OETF) for the C300 Mark II The Canon Log2 curve was radically redesigned over Canon Log at the lower end (below 5 IRE) to do far greater justice to reproduction of the all-important lower tonal ranges that can now be achieved by the exceptional 15-Stop exposure latitude of the C300 Mark II.
10.0 HDR combined with a Unique Sensitometric Characteristic The proprietary signal extraction strategies within the CMOS image sensor facilitate a remarkable control over the disposition of exposure latitude above and below the 18% reference gray exposure. At low ISO levels the master gain control is implemented by the digital gain control in the external image processing system (shown in Figure 2).
Figure 9 Showing the four color gamut choices in the C300 Mark II The unusually wide Cinema Gamut is intended to support digital movie production where the production team might wish to emulate (in the color grading process) the look of a specific motion picture film stock. This unusually wide color gamut encompasses the color gamut of all known film stocks used in motion picture production today and in the past.
1. High Sensitivity – the exceptionally high sensitivity of the image sensor supports image capture in those infrequent situations where scene illuminace is unusually low (the camera supports sensitivity settings up to ISO 102,400). This level of sensitivity also offers creative flexibilities in setting ND filters, lens aperture, and electronic shuttering – for controlling depth of field – over a range of low light situations.
10. 4:4:4 Coded RGB 2K / HD video components – provides the maximum color space to support sophisticated color grading as well as Bluescreen and Greenscreen compositing for special effects 11. High Bit Depth – up to 12-bit RGB for 2K / HD origination effectively eliminates digital quantization artifacts and noise, while ensuring faithful reproduction of the wide dynamic range and wide color gamut to support extensive color grading in postproduction.
REFERENCES [1] Canon White Paper: New 35mm CMOS Image Sensor for Digital Cine Motion Imaging [2] Canon White Paper: RGB Resolution Considerations in a New CMOS Sensor for Cine Motion Imaging [3] Canon White Paper: Extended Recording Capabilities in the EOS C300 Mark II [4] SMPTE ST 2048-1:2011 2048 x 1080 and 4096 x 2160 Digital Cinematography Production Image Formats! [5] SMPTE ST 2036-1:2009 Ultra High Definition Television – Image Parameter Values for Program Production [6] SMPTE ST 274M – 200