The Sony “Star Eater” (2017)
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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.
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.
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.
https://blog.kasson.com/a7riv/sony-a7riv-edr-in-continuous-c...
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...
Just clumsiness with ergonomics and weird design.
My preference on ergonomics and color has long been Canon -> Nikon -> Sony distant last
If the camera is unwieldy to use and I miss the shot I don't care about a little more dynamic range and these other things. Ergonomics is very personal though so some people are going to hate Canon and love Sony or Nikon.
The constant harping about dynamic range & high ISO noise is always hilarious. Every brand has ridiculous high ISO and amazing dynamic range compared to so many films back in the day. 1600 used to be stupid high ISO!
We have it staggeringly easier & cheaper than in the past and yet everyone just constantly complains way more than in the past.
If you knew any of the techniques from film it's super easy to work around any of these things. It's always hilarious to see sites like dpreview write articles where they make a case for one camera being the only way to do something cause it's got a little more dynamic range and they completely ignored all the old techniques that will instantly make the shot work on any of the cameras, and look better than the way they did it with the "superior" camera.
I agree about the ergonomics, for most people. Im the odd one in that I really like Sony ergo.I disagree completely about colour. All three cameras brands have the exact same colour, the only difference in colour rendition is dynamic range and JPEG processing (which you shouldn't rely on).
I went with Sony because Canikon didn't have a mirrorless camera at the time, are much more expensive, (Sony makes by far the cheapest full-frame camera, new and used), and you can't beat Sony for adaptability. You can adapt essentially any lens to Sony, and even add AF.
Also, sometimes these techniques just can't do it.
This kind of thing is a reason I did not get a Z7. Compared to a D850, the Z7 "bakes in" processing even to RAW files.
At first when testing a Z7 I could not understand why the images in Lightroom looked like mobile phone photos. I tested a Z7 and a D850 while physically standing on the same spot and using the same lenses. The Z7 looked like overprocessed garbage, the D850 was flawless, natural, and creamy smooth in its tonality.
It took me ages to realise that the Z7's "unprocessed" look is actually processed, and that you have to undo the processing manually. At which point the pictures look virtually identical to the D850, as expected since the sensors are nearly identical.
I couldn't believe Nikon would do something this amateurish for a flagship product.
I guess the marketing team thought they needed the camera to be "familiar" for people upgrading from mobile phones or something silly like that...
Agreed, especially in terms of UI. I shoot A7RIV and Fuji X-T3 and the Fuji is so much nicer to use. Technically though, it's fairly good these days.
> Can you confidently count on getting 14 bit RAW files, or will you sometimes only get 12 bits?
On the latest generation they've largely fixed this [0]. 12-bit if you use compressed RAW, 14-bit if you don't.
> Are their RAW files losslessly compressed like every other manufacturer's?
No. Turn off compression, problem solved.
[0]: https://phillipreeve.net/blog/an-upgraders-guide-to-the-sony...
Not really. I do a lot of astrophotography with a DSLR, but use the DSLR effectively as a mirrorless camera. I also regularly wedge in filters that prevent use of the SLR mechanism anyway. Considering my total exposure times are regularly in excess of 2 hours, heating isn't really any different from mirrorless, and mirrorless would be a blessing for its versatility and simplicity.
The only real way to combat heat issues for exposures that long is a cooled sensor.
I still want to pick up an a7sII. We mounted that to a telescope and cranked up the ISO. We could identify DSO as the telescope slewed to the next subject. It made framing super simple. Once framed, we'd drop the ISO back to realistic numbers for the actual image to be taken. With my DSLR, I'd have to take a 15 sec exposure just to see what I was looking at, and rinse-repeat for each adjustment.
The fact that the sensor is on for about 95% of the time through that process means that the heat isn't any different than a mirrorless setup.
Dark frame subtraction corrects reasonably well for this anyway. Cooled camera would perform better but that's a lot more trouble than it's worth for me as a hobbyist. I wouldn't recommend cooling with ice packs though. You want your sensor at a constant temperature through most of the data collection so that your dark frames actually work. If the temperature of the sensor fluctuates, your dark frames become not representative of the actual dark currents most of the time.
That is pretty much the only thing that I have found about ML that I don't like. Everything else about it makes my camera a much better system. ETTR is my fave!
It is admittedly hard to get the intervalometer to switch off though, often it keeps restarting itself after several restarts of the camera but eventually gives up.
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.
https://petapixel.com/2018/06/08/sonys-star-eater-problem-ha...
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.
But those features are designed to be beneficial in most cases, and this article is about the edge cases where some faint stars, in some photographs might look a little different if you examine the image at 1:1. Its an interesting article from a technical standpoint, but I'd say the feature does more good than harm in the vast vast majority of situations.
Also, most dedicated astro folks, especially the ones doing deep space imaging (i.e. beyond just capturing the mikly way) are probably using dedicated astro cameras.
https://www.usa.canon.com/internet/portal/us/home/products/d...
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.