If you were hoping that Sony had finally completely removed the spacial filtering that causes its high-resolution a7R cameras to "eat stars," you're going to be disappointed. According to Jim Kasson, the Sony a7R IV eats stars to about the same degree as the a7R III.
Over the last year or so, firmware updates from Sony introduced a much-publicized penchant for Sony Alphas to “eat” stars even in RAW files, apparently due to an internal noise reduction or anti-aliasing routine users could not turn off. Stars were smoothed away along with the noise in exposures longer than 3.2 seconds in some Sony cameras (and longer than 30 seconds in others). I feel that in the a7 III, the Star Eater has now been largely vanquished.
Has Sony actually fixed its "star eater" issue in the new a7R III? Photographer Drew Geraci tested the camera earlier this month and found that the problem "is no more," but now new reports are suggesting that the a7R III does indeed still "eat" stars and cause them to disappear in long exposures.
Sony's latest mirrorless cameras have incredible specs and glowing reviews, but astrophotographers have been complaining about a "star eater" issue in which stars are mistaken for noise and removed from long exposure photos. There's some good news, though: it looks like the new Sony a7R III doesn't have the "star eater" problem.
Sony recently released firmware v.4.0 for its a7S II and a7R II mirrorless cameras. The announcement that this firmware version “Improves image quality when Long Exposure NR setting is off” raised hopes for many photographers that Sony had at last addressed the issues caused by their automatic smoothing of all exposures of 4 seconds or longer, sometimes referred to as the "Star Eater" effect because of the way that it removes stars in astrophotography images.
Sony has just released a wave of new firmware updates for its mirrorless cameras. Found among the various fixes and improvements are solutions to the a9 overheating warning issue and the "star eater" issue reported by astrophotographers.
Sony makes excellent cameras. In the last few years, they launched a completely new full frame camera system that has pushed the bounds of digital photography. I switched entirely to Sony gear after first seeing the tremendous low-light capability of their a7S and have enjoyed many outings shooting astrophotography on many different Sony camera bodies since.