
The Sony “Star Eater” (2017) - mjamm95
http://www.markshelley.co.uk/Astronomy/SonyA7S/sonystareater.html
======
ben7799
I've been aware of this for a really long time.

There's no super easy way around this but Sony has been really clumsy about it
for a long time.

Canon has long let you turn this off, probably close to 15 years ago they
implemented this as a custom function? Canon's implementation is to actually
take a second picture where it doesn't flip the mirror up, so you get a dark
frame and it tries to map any hot pixels that way and subtract them from the
final image. The annoyance with the Canon way is that it takes 2x as long. If
you're doing a 5 minute bulb exposure it now takes 10 minutes. And if you
screwed it up the sky has now changed, 10 minutes is an eternity.

Way way back about 20 years ago I really decided I hated Sony's way of making
digital cameras, long before DSLRs were accessible.. they learned a lot by
buying out by Minolta but they still have done a lot of clumsy stuff. Their
lead on Dynamic Range has been trumpeted by places like DPreview for years as
the only thing that matters at all with cameras but if they do other stuff
clumsily the Dynamic range doesn't matter to me. A lot of this was ergonomics,
but they had a previous episode where they had cameras that were applying
noise reduction to RAW photos and causing people headaches. (I believe
astrophotographers were also put off by that episode.)

I get the impression that mirrorless cameras are going to be a step back on
all brands for astrophotography due to heat issues.

~~~
spchampion2
Sony cameras have clumsiness all over the place. Can you confidently count on
getting 14 bit RAW files, or will you sometimes only get 12 bits? Are their
RAW files losslessly compressed like every other manufacturer's?

These issues are what drove me to buy a Nikon Z7. I will also be honest in
saying that with this decision I've traded off a camera system with weird
problems for a camera system that's mostly missing the rest of the system.

~~~
sudosysgen
I have absolutely never had issues with bit depth and dynamic range. In fact,
my A7ii generally has more dynamic range than my friends on Canikon.

Sony is pretty open on their websites that their RAW files when compression is
activated may have loss of bit depth in some cases. You can turn off RAW
compression in about 3 button presses, and then you'll always have 14bit
files.

~~~
spchampion2
The camera drops to 12 bit when shooting in some modes such as continuous,
bulb, or long exposure. This is true all the way to the A7rIV and the A9II as
far as I know. Here's an article with analysis:

[https://blog.kasson.com/a7riv/sony-a7riv-edr-in-
continuous-c...](https://blog.kasson.com/a7riv/sony-a7riv-edr-in-continuous-
compressed-mode/)

Here's a Sony site with the breakdown of the different bit depths you get in
different modes for different cameras (note that ILCE-7RM4 is the A7rIV):

[https://www.sony.ca/en/electronics/support/e-mount-body-
ilce...](https://www.sony.ca/en/electronics/support/e-mount-body-
ilce-7-series/ilce-7m2/articles/00229990)

~~~
sudosysgen
As your link is saying, this behaviour is only in compressed RAW mode,
starting from the A7iii. You can disable RAW compression and be assured that
you will get 14 bits all the time. This is all normal behaviour.

~~~
labcomputer
Maybe I’m misunderstanding the link, but it appears to list several
configurations where shooting _un_ compressed raw results in 12 bits.

~~~
sudosysgen
Yes, on cameras older than the A7iii, except in modes with significant noise
reduction where the bits are useless anyways.

------
gnu8
I wonder why not provide a switch to turn off the star eater? Bury it under
some menus so people don’t use it unless they go looking.

~~~
kmlx
considering the huge sony camera menu, i am sure it's somewhere in there:
[https://m.imgur.com/PODOrwY](https://m.imgur.com/PODOrwY)

~~~
arriu
I think the issue here is that even with Long Exposure NR and High ISO NR
turned off, Sony still does it anyways.

~~~
mikeyouse
This is an old article - you're right that's how it used to be handled
(silently and without a menu to disable) but it's been fixed in all the
firmware shipped since 2018.

~~~
terramex
It has not been fixed, only changed to be less destructive on green channel.
The article has a second part describing those changes:
[http://www.markshelley.co.uk/Astronomy/SonyA7S/sonystareater...](http://www.markshelley.co.uk/Astronomy/SonyA7S/sonystareater_v2.html)

Many people do not see that issue or claim that it was 'fixed', because they
do not have optics sharp enough to resolve stars to 1x1 or 2x2 pixels.

~~~
mikeyouse
Ah, interesting. I've only experienced it on the A7iii, which has it fixed
more or less completely (none of the green blobs or any errors showing up in
the article you linked).

[https://petapixel.com/2018/06/08/sonys-star-eater-problem-
ha...](https://petapixel.com/2018/06/08/sonys-star-eater-problem-has-been-
defeated-in-the-a7-iii/)

~~~
terramex
It still exists on A7 III: [https://blog.kasson.com/a7iii/a7iii-long-exposure-
spatial-fi...](https://blog.kasson.com/a7iii/a7iii-long-exposure-spatial-
filtering/)

Those are noise power density graphs that show that signal went through a low-
pass filter. On Sony cameras without 'star-eater' and cameras from other
manufacturers it is flat.

But I admit that this issue is most noticeable on S-series (low
resolution/high sensitivity) cameras, as their lower resolution makes it
easier to resolve stars down to 3x3 pixel size. Normal and R-series cameras
have such high resolution that it is hard to notice and not much of a problem
in amateur astrophotography.

I have not seen any proper tests of latest A7S III as it was only released
last month.

------
pabs3
Is there any open source firmware for these cameras that doesn't have the same
issue?

~~~
numpad0
Digital cameras in general are difficult to unbrick, so not very often
examined in depth

------
neilv
Canon made a DSLR variant specifically photo astrophotography, the 20Da, which
I understand had a cut filter removed, and maybe other differences. I don't
know whether it had changes to the image processor or default settings for
that.
[https://astrobackyard.com/canon-60da/](https://astrobackyard.com/canon-60da/)

~~~
ISL
That line continues with the EOS Ra.

[https://www.usa.canon.com/internet/portal/us/home/products/d...](https://www.usa.canon.com/internet/portal/us/home/products/details/cameras/eos-
dslr-and-mirrorless-cameras/mirrorless/eos-ra)

------
gitpusher
Interesting. I shot the night sky recently with my Sony a6300 and a cheap
Sigma 19mm wide-angle lens. After reading this article, I reviewed some of
those photos.

I don't see any examples of the star "punching" effect, but this might be the
result of bad focusing, etc. as the article mentions.

~~~
terramex
Sony's crop sensor cameras like a6300 only use this filtering in Bulb Mode.

~~~
sudosysgen
In 2020, this issue is only present in Bulb Mode or on the a7Rii and a7Sii for
1x1 stars.

------
iqandjoke
May we kindly know does it apply for Apple iPhone iOS as well?

