C3 Series CMOS Cameras
C3 cameras employ the latest generation of Sony IMX CMOS sensors, offering exceptional quantum efficiency thanks to back-illuminated design and very low dark current. Despite relatively small pixels, full-well capacity exceeds 50 ke-. Combined with full 16 bit digitization, perfectly linear response to light and exceptionally low read noise, these cameras are suitable for both aesthetic astro-photography as well as astronomical research. Sensor formats from APS to photographic full-frame (24 × 36 mm) ensure wide field of view and optimally utilize capabilities of the optical systems most commonly used by amateur astronomers. C3 cameras are equipped with Sony IMX rolling shutter back-illuminated CMOS detectors with 3.76 × 3.76 μm square pixels. Despite the relatively small pixel size, the full-well capacity over 50 ke- rivals the full-well capacity of competing CMOS sensors with much greater pixels and even exceeds the full-well capacity od CCD sensors with comparable pixel size.
The used Sony sensors are equipped with 16-bit ADCs (Analog to Digital Converters). 16-bit digitization ensures enough resolution to completely cover the sensor exceptional dynamic range.
Consumer grade sensors. The sensor manufacturer (Sony Semiconductor Solutions Corporation) limits their usage to consumer still cameras only with operation time max. 300 hours per year.
Industrial grade sensors, intended for devices operating 24/7.
C3-26000 and C3-61000 with consumer grade sensors, intended for max. 300 hours a year operation.
C3-26000 PRO and C3-61000 PRO with industrial grade sensors.
C3 camera models with consumer-grade sensors include:
Model C3-26000 C3-61000 C3-26000C C3-61000C CMOS sensor IMX571 IMX455 IMX571 IMX455 Sensor grade Consumer Consumer Consumer Consumer Color mask None None Bayer RGBG Bayer RGBG Resolution 6252 × 4176 9576 × 6388 6252 × 4176 9576 × 6388 Pixel size 3.76 × 3.76 μm 3.76 × 3.76 μm 3.76 × 3.76 μm 3.76 × 3.76 μm Sensor size 23.51 × 15.70 mm 36.01 × 24.02 mm 23.51 × 15.70 mm 36.01 × 24.02 mm
C3 camera models with industrial-grade sensors include:
Model C3-26000 PRO C3-61000 PRO C3-26000C PRO C3-61000C PRO CMOS sensor IMX571 IMX455 IMX571 IMX455 Sensor grade Industrial Industrial Industrial Industrial Color mask None None Bayer RGBG Bayer RGBG Resolution 6252 × 4176 9576 × 6388 6252 × 4176 9576 × 6388 Pixel size 3.76 × 3.76 μm 3.76 × 3.76 μm 3.76 × 3.76 μm 3.76 × 3.76 μm Sensor size 23.51 × 15.70 mm 36.01 × 24.02 mm 23.51 × 15.70 mm 36.01 × 24.02 mm
Camera Electronics
CMOS camera electronics primary role, beside the sensor initialization and some auxiliary functions, is to transfer data from the CMOS detector to the host PC for storage and processing. So, as opposite to CCD cameras, CMOS camera design cannot influence number of important camera features, like the dynamic range (bit-depth of the digitized pixels).
Sensor linearity
The sensors used in C3 cameras show very good linearity in response to light. This means the camera can be used for advanced research projects, like the photometry of variable stars and transiting exoplanets etc.
Download speed
C3 cameras are equipped with on-board RAM, capable to hold several full-resolution frames. Downloading of the image to the host computer thus does not influence image digitization process, as the download only transfers already digitized images from camera memory.
Time needed to digitize and download single full frame depends on USB connection type.
Model C3-26000 C3-61000 Full-frame, USB 3.0 (5 Gbps) 0.22 s 0.44 s Full-frame, USB 2.0 (480 Mbps) 1.16 s 2.73 s
If only a sub-frame is read, time needed to digitize and download image is naturally lower. However, the download time is not cut proportionally to number of pixels thanks to some fixed overhead time, independent on the sub-frame dimensions.
Model C3-26000 C3-61000 1024 × 1024 sub-frame, USB 3.0 (5 Gbps) 0.03 s 0.05 s 1024 × 1024 sub-frame, USB 2.0 (480 Mbps) 0.06 s 0.06 s
C3 camera electronics supports in-camera 2 × 2 binning. If this binning mode is used, download speed increases because of less amount of data read from camera.
Model C3-26000 C3-61000 Full-frame 2 × 2 binning, USB 3.0 (5 Gbps) 0.16 s 0.30 s Full-frame 2 × 2 binning, USB 2.0 (480 Mbps) 0.29 s 0.69 s
Download speed when using the Moravian Camera Ethernet Adapter depends if the 100 Mbps or 1 Gbps Ethernet is used, if USB 2 or USB 3 is used to connect camera to Ethernet Adapter device, but also depends on the particular network utilization etc. When the camera is connected to the Ethernet Adapter using USB 3 and 1 Gbps Ethernet is directly connected to the host PC, download time of the C3-61000 full frame is approx. 2.5 s.
Camera gain
Sensors used in C3 cameras offer programmable gain from 0 to 36 dB, which translates to the output signal multiplication from 1× to 63×.
Camera driver accepts gain as a number in the range 0 to 4030, which corresponds directly to sensor register value. This number does not represent gain in dB nor it is an exact gain multiply. However, the driver offers a function, which transforms the gain numerical value to gain expressed in dB as well as multiply. Some selected values are shown in the table:
Gain number Gain in dB Gain multiply 0 0.00 1.00× 1000 2.34 1.32× 2000 5.82 1.95× 3000 11.46 3.74× 4000 32.69 43.11× 4030 35.99 63.00×
Conversion factors and read noise
Generally, many sensor characteristics depend on the used gain. Also, the used sensors employ two conversion paths. One path offers very low read noise, but cannot utilize full sensor dynamic range. Another conversion path offers maximum pixel capacity, but at the price of higher read noise. The cross point is set to gain 3× (approx. 10 dB), where the full well capacity drops from more than 50 ke- to ~17 ke-. The read noise then drops from ~3.2 e- RMS to ~1.5 e- RMS.
Gain number Gain in dB Gain multiply Conversion factor Read noise RMS Full well capacity 0 0.0 dB 1× 0.80 e-/ADU 3.51 e- 52,800 e- 2749 9.7 dB 3× 0.26 e-/ADU 3.15 e- 17,100 e- 2750 9.7 dB 3× 0.26 e-/ADU 1.46 e- 16,900 e- 4030 36.0 dB 63× 0.18 e-/ADU 1.39 e- 11,600 e-
At gain = 0, dynamic range is 52,800 / 3.51 = 15,043×
At gain = 2750, dynamic range is 16,900 / 1.46 = 11,575×
Also, it is worth noting that in reality the noise floor is not always defined by read noise. Unless the camera is used with very narrow narrow-band filter (with FWHM only a few nm) and under very dark sky, the dominant source of noise is the sky glow. When the noise generated by sky glow exceeds approximately 4 e- RMS, extremely low read noise associated with gain set to 2750 or more is not utilized and dynamic range is unnecessarily limited by the lowered full well capacity.
Gain set to 2750 can be utilized if imaging through narrow-band filter with appropriately short exposures, so the background noise does not exceed the read noise. This is typical for aesthetic astro-photography, where the lowered full well capacity does not negatively influence the result quality.
But even without narrow-band filters, the extremely low read noise allows stacking of many short exposures without unacceptable increase of the stacked image background noise, caused by accumulation of high read noise of individual exposures.
Gain set to 0 offers maximum full well capacity and the greatest sensor dynamic range, which is appreciated mainly in research applications. Pass-bands of filters used for photometry are relatively wide and dominant source of noise is the sky glow.
But also for RGB images, used for aesthetic astro-photography, higher dynamic range allows longer exposures while the bright portions of the nebulae and galaxies still remain under saturation and thus can be properly processed.
Binning
The camera driver and user’s applications offer wide variety of binning modes up to 4 × 4 pixels as well as all combinations of asymmetrical binning modes 1 × 2, 1 × 3, 1 × 4, 2 × 4 etc. To allow such flexibility, binning is performed only in the camera driver (software binning) and does not rely on the limited capabilities of the hardware binning.
The negative side of software binning is the same download time like in the case of full-resolution 1 × 1 mode. For typical astronomy usage, the small fraction of second download time is irrelevant, but for applications sensitive to download time, the hardware 2 × 2 binning can be useful.
商品属性 [Pixel Size] 3.76 × 3.76 μm [Spatial Resolution] 9576 × 6388 [Sensor size] 36.01 × 24.02 mm