If you wanted a large CCD chip, you had to go Kodak. They are far inferior to the Sony CCD, but juist bigger. Dark Noise has always been higher with the Kodak. I use Dark Frame Subtraction on Image subs but not Flat Frames. I now use a Starlight Xpress Trius SX46 (Kodak KAF 12600). Kodak CCD chips have alway required Dark Frame Subtraction with the image subs. The older Sony chips such as the HX-916 did require Dark Frame Subtraction, but from the H9 on they did not. I have used Starlight Express CCD cameras since 2005. Bias frame subtraction is used only for all types of sub frames with those chips. Dark frame subtraction can actually add noise to the sub frames with those chips. Typically Sony HAD CCD chips to not need Dark Frame Subtraction at all. In some CMOS cameras including my ZWO 178 the circuitry does not behave consistently at too short exposures so you naturally gravitate towards longer flats (and dark flats). This regardless of sensor tech (CCD or CMOS), although on CCDs read noise is higher so simple bias frames typically work for longer flats than CMOS. If your flats are longer than 3 seconds (not unusual in narrowband or if your flat source is too dim) you will probably start seeing those things and it's time for dark flats. The longer your flats though, the more sense it makes to use dark flats because dark current, hot pixels and amp glows become significant. For such small durations thermal signal is not really a thing and both kinds of subs contain essentially the same readout noise, which by the way is quite high on CCDs. There is a difference with the ZWO 178MM and MC, where I take dark flats.
They produce pretty much the same master sub which by the way is very close to zero almost everywhere and has no noticeable effect on flat field correction and I feel a little silly for using it but it doesn't cost me anything. There is no difference between flat darks and bias with my D7500.
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