A7IV Star Eater - 4 sec without and with USM, compared to 3.2 sec

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Magnar W
Magnar W Veteran Member • Posts: 6,746
A7IV Star Eater - 4 sec without and with USM, compared to 3.2 sec
8

Doing tracked astrophoto with your A7IV? Here you can see how the smoothing effect of spatial filtering (popular name: Star Eater) can be mostly restored by adding a small amount of Unsharp Mask. Faint stars, except for some very faint and less saturated stars looking like small grey blobs, will pop up again, sice they are not removed, just smoothed out. I have used this simple technique for years for my A7 and A7rIII astro files. When using a tripod and no tracker, the Star Eater is a non-issue.

Other camera brands also use spatial filtering for long exposures. The Sony filtering is noticeable because it kicks in at a given exposure speed, for most modern Sony cameras at 4 sec exposure, but nothing at 1/3 stop faster, 3.2 sec.

Process:
Uncompressed RAW files.
Camera on a tracker.
Lightroom, brightened, but no contrast, sharpness or noise reduction.
Put together in Photoshop, USM added for the middle 4 sec frame.
No additional image editing.

Well, here are 100% crop, taken with different very sharp primes wide open. The results between different focal lengths are far from dramatic.

You are free to repeate the test if yopu want to control the results.

 Magnar W's gear list:Magnar W's gear list
Sony a7 Sony a7R III Sony a7 IV Sony FE 24-70mm F4 OSS Sony FE 90mm F2.8 macro +4 more
Sony a7
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