Photometric Parameters of the Canon EOS 6D Mark II Camera

Abstract

The paper presents metrological parameters of the full-frame camera Canon EOS 6D Mark II’s photosensor. The working range of output signal levels is from 0.1 to 15 870 reference units DN. Depending on ISO parameter value, the sensor solarization takes place when the output signal reaches levels from 11 318 up to 15 870 DN. According to the data of laboratory experiments, it is shown that the range of the photosensor output signal in the area of its linear response to changes in the active light flux is 20.2–20.4 dB (ΔS is 107.3–11 595.6, 142.0–14 819.9, and 132.2–14 309.0 DN in R, G, and B channels of the sensor, respectively.) When using the logarithmic function of photosensor sensitivity, the range of its linear response increases to 38.2 dB (ΔS = 2.24–14 819.9 DN). The sensor’s local response in the R, G, and B channels to changes in active light flux is 558.63, 1164.0, and 691.37 DN/s at ISO 100; 1283.5, 955.29, and 206.9 DN/s at ISO 12 800; and 4263.6, 3119.2, 698.42 DN/s at ISO 40 000, respectively. The dependence of the sensor output signal level on the ISO value at an exposure time of T_exp = 5.2 s remains linear within the entire range of ISO values from ISO 100 to ISO 102 400 in all spectral channels of the sensor when using a logarithmic dependence log Se(log ISO). In the case when the sensor transfer function is presented on natural numbers scale, the sensor linear response ranges in R, G, and B spectral channels differ and are ΔISO_R,G,B = 1600–102 400, 2016–102 400, 3200–102 400 DN, respectively. In the highest informativeness areas of the linear sensor response ranges, the signal-to-noise ratio (SNR) of the output signal takes values from 5.0 dB to 34.5 dB (Rose’s criterion); accordingly, the signal increases from 4.5 to 12 560 DN and is controlled by the ISO level. Similarly, when the signal intensity depends on exposure duration, at ISO 100 within the sensor linear response ranges, the critical SNR values of output signals are 5.0 dB at S_av = 14.0 DN and 47.6 dB at S_av = 14 820 DN. At ISO 40 000, the SNR parameter takes values from 5.0 dB to 33.6 dB at signal levels of 160–230 and 13 522 DN, respectively. Taking into account the results of conducted analysis, the use of digital cameras with a CMOS sensor in photometric studies can be considered acceptable.