We sent some files to our friend Jim Kasson for analysis, and he confirms that the Sony a7R III is definitely still a Star Eater, despite several claims to the contrary that have been published online over the past week.
Looking at Kasson’s graphs, one can clearly see the noise reduction kick in near Nyquist in Kasson’s energy plots. Indeed, in our own shots of the stars with the a7R III and latest a7R II (firmware v3.00 and above), our final files only show stars that are larger than one pixel with a few neighboring pixels: suggesting that smaller stars are indeed ‘eaten’ or dimmed due to a spatial filtering algorithm.
|At a 3.2-second exposure, the ‘spacial filtering’ (Star Eater) is very mild, and won’t affect your stars.|
|But as soon as you hit 4-seconds, spacial filtering kicks in big time, causing the same Star Eater problems that was seen in the a7R II|
This is a missed opportunity for Sony, and something dedicated astrophotographers will want to consider when deciding between the a7R III and other options that don’t have this same issue (a Nikon D850 for example). Other photographers happy with the number of stars still in their shots simply won’t care.
We’ll drop in one of our sample photos shortly for your pixel-peeping pleasure. But for now, we can say this with confidence: while a lot of stars still survive ‘Star Eater’, the a7R III continues the trend of noise reduction that dims or erases small stars at exposure longer than 3.2s.