How to Fix Sony Star Eater on the a7SII and a7RII (Continuous Shutter Mode Workaround)

Alas, a partial fix to the dreaded “star eater” issue has been found for the a7SII and a7RII! The quick version: enable continuous shutter drive mode. Read more to learn about the “star eater” issue and the limitations of this partial fix.

Sony’s a7SII and a7RII have an issue that affects astrophotography when they’re used for exposures of 4 seconds and longer. Photographs of the night sky made with these cameras (especially the a7SII) are subject to a built-in processing that mistakes stars for noise and “eats” them or reduces their brightness. The issue also affects other Sony Alpha cameras in different scenarios.

The result of the issue is an astrophoto with reduced number of visible stars and an appearance of reduced resolution in the night sky. Stars are often also color shifted to false colors as a result of the problem. Since the issue affects stars at the pixel level, the problem is especially prevalent on the relatively low-resolution sensor of the a7SII. I have documented this issue thoroughly and noted how it affects most Sony Alpha cameras on my post about the so-called “star eater” problem. With a little bit of searching, you can find many other posts about the issue across the astrophotography and photography communities that confirm the problem.

One of the best sets of analyses of the issue came from Jim Kasson’s blog posts. He shows that with a frequency analysis of a color channel on the a7RII and a7SII, exposures of 4s and longer have attenuation at higher spatial frequencies. Basically, small bright pixels are filtered out. For a long time, this has been a problem a7RII and a7SII users have had to live with for months. But now, we have Jim Kasson to thank for making us aware of a partial fix.

The Workaround

Sony a7SII Continuous Drive Mode
Star Eater Workaround: Enable Continuous Drive Shutter Mode

In a December 2017 post, Jim Kasson talked about a potential workaround on the a7RII. The fix is certainly counter-intuitive: enabling continuous drive mode while shooting long exposures. In his analysis, Jim shows that by enabling the continuous drive mode, the a7RII no longer exhibits the same behavior of the star-eating algorithm. Jim’s original analysis was only of the a7RII so I was curious to see if the same workaround would work on the a7SII. I had a friend supply some sample dark-frames from his a7SII and I took a close look at the files. Sure enough, enabling continuous mode seemed to prevent the star eater problem from occurring. I sent the frames to Jim for his final analysis of the a7SII star eater workaround which he has published here.

  • So the good news: a7RII and a7SII users can circumvent the Sony star eater issue by shooting with continuous shutter mode enabled. Either regular “Continuous” or “Continuous Speed Priority” shutter modes will work.
  • The bad news: by enabling continuous shutter mode, the color depth of the raw files is reduced to 12-bit. This means that the file is losing some dynamic range capability and may show some increase in noise. In all practicality, the results should be more desirable for astrophotography than the star-eaten files.
  • Another problem that persists: Bulb exposures are still affected because continuous shutter mode cannot be enabled in Bulb mode and vice-versa. Furthermore, the new a7RIII is still affected, regardless of shutter drive mode. 

Closing Thoughts

Why didn’t we find this earlier?

It’s extremely well hidden. Under no circumstances does usually it make sense to shoot with continuous shutter modes while shooting long exposures. Normally, it’s a shutter mode reserved for sports and wildlife shooting. There isn’t a single reason to enable continuous shutter mode for astrophotography since our shutter times tend to be very very long.

But now that it’s out, this workaround is a welcome find for owners of the a7RII and a7SII who enjoy shooting astrophotography but it’s still only a partial fix. Using the workaround, bit-depth is slightly reduced, limiting the dynamic range of the resulting photographs. It’s also unfortunate that the problem still persists in Bulb mode and there’s no workaround for Bulb shooting known at this time. Ultimately, it’s dreadfully disappointing that this issue even exists in the first place. It’s a shame that Sony still has not issued a firmware fix to allow us to disable the spatial filtering altogether. I and several other astrophotographers are supporters of the open petition to Sony to fix the star eater issue altogether.

For a more complete documentation, see my article and open letter to Sony about the star eater issue.

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47 Replies to “How to Fix Sony Star Eater on the a7SII and a7RII (Continuous Shutter Mode Workaround)”

    1. a7ii is not affected by the star eater issue it seems (except when shooting in BULB mode).

  1. Ian, you said you still use your A7S. Does that mean that there is a star eater workaround for it already? (eg. staying at a lower firmware, setting) Also, have you used the loxia 50 for panorama stitching on your A7S before? If so, how did you like it? Thanks for your time and keeping us updated on the star eater issue.

    1. Wow. I am sorry. I swore I read your “Open Letter” post thoroughly. Please ignore or delete my comment.

  2. Okay. Posted before under the primary star eater topic on this site that I wasn’t seeing any issues with my A7Rii. So, of course I had to try this hack. Compared 30 second exposures using a tracker and 180mm Nikkor manual lens. Single shutter mode vs continuous (low). Aperture and ISO were kept constant.

    Reviewing the full pictures on a 27″ monitor with LR side by side mode…hard to see any difference. Magnify at 1:1 and yes…something is better in the continuous mode picture, but it’s subtle. Magnify at 4:1 and…hello! A lot of tiny…one pixel maybe…stars in continuous mode are not there in single shot mode. A lot…as in all of them. Yeah, the star eater filter really does a fine job of extracting all the tiny stars. Also, the image doesn’t seem as sharp in single shutter mode, maybe the star eater is smoothing also (or maybe the focus moved slightly).

    So…when is someone going to find a hack for bulb mode filtering on the A7Rii??? Hero worship will ensue.

    1. Daniel, your description is a really great characterization of the issue. It’s definitely a pixel peeper issue. And yes, because of the way that the star-eater issue tries to remove noise, brighter stars end up softer as if focus was off… even though it wasn’t. As far as Bulb mode on Sony cameras…. I think we’re s-out of luck.

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