Multiple Readout Modes are special for QHY 16-bit Cameras (QHY600/268/461/411). Different readout modes have different driver timing, etc., and result in different performance. These readout modes are currently supported in the QHYCCD ASCOM Camera Driver, SharpCap and N.I.N.A.
Readout Mode #0 (Photographic DSO Mode). This mode is suitable for most DSO imaging situations. In this mode you don’t have to care about unity gain, because gain0 is good enough for a 16-bit sensor; however , there is a drop in the noise between Gain 25 and Gain 26.
Readout Mode #1 (High Gain Mode). This mode is something like double native iso of some new digital cameras, whose danamic range can greatly incerase at the vary high iso value, like iso800, iso3200, etc. The high gain mode provide such improvement for QHYCCD 16bit cameras. We recommend you choose this mode when you have to capture at high gain, for example, a vary dark object. Please note the switch point of HGC/LGC of QHY600/268/461 is 56. That means you must set the gain value equal or a little larger than 56 under this mode to make the best of it.
Readout Mode #2 (Extended Fullwell Mode). With a pixel size of 3.76um, these sensors already have an impressive full well capacity of 51ke. Nevertheless, QHYCCD has implemented a unique approach to achieve a full well capacity higher than 51ke- through innovative user controllable read mode settings. In Extended Fullwell Mode, the QHY600 can achieve an extremely large full-well charge value of nearly 80ke- and the QHY268 can achieve nearly 75ke-. Greater full-well capacity provides greater dynamic range and large variations in magnitude of brightness are less likely to saturate.
Readout Mode #3 (Extended Fullwell Mode-2CMS). While Extended Fullwell Mode has large fullwell, it brings more noise, too. Don’t worry, the 2CMS mode can reduce readout noise by about 1.3 times while keeping the same full well value and system gain as the #2 mode Extended Fullwell mode, by secondary sampling. We recommend this 2CMS mode more than mode #2 when you need larger fullwell. By the way, it’s better to use gain 25 or 26 ranther than gain0 under Mode#3