Review of the Sony A7S

[sharkmelley]

Hi Craig. 

Previously I used a Canon camera so I already had the Canon telescope adaptors.  When I bought the Sony I simply bought a Sony adapter for Canon lenses then I could attach the Sony camera wherever the Canon camera used to go.  Simple!

Mark

[Craig123]

1 hour ago, sharkmelley said:

Hi Craig. 

Previously I used a Canon camera so I already had the Canon telescope adaptors.  When I bought the Sony I simply bought a Sony adapter for Canon lenses then I could attach the Sony camera wherever the Canon camera used to go.  Simple!

Mark

Thanks Mark..makes sense.I thought my problem was my Skywatcher Ed80 pro was not fast enough to get decent shots. using the A7 .I was doing 2 mins subs at iso 1600 of Andromeda and got alot of them but didnt bring as much detail out as i hoped.I put the reducer on to get it from f7.5 to 6.4 and tried 10 mins with guiding but the adaptor is too long so the detail is better but its too distorted.Carole on here mentioned you do subs of 30 secs but your scope will be better i should expect.I spotted your super shot of Andromeda on Astrobin.Could i ask What kind of iso did use on that,and how many subs?..i often use it at 5000 on landscape type  shots for 20-30 secs.Your pic has given me abit of renewed hope !

[sharkmelley]

Look at my website (in my signature) and you'll find details of all my shots.  Are you using an A7 or an A7S - you've mentioned both.  There's a big difference between them. The A7S is the king of low-light cameras and is well suited to slow scopes because of its very low read noise and well controlled thermal noise.

The reason I use 30sec exposures is because for longer exposures I would need bulb mode and bulb mode invokes the "star eater" spatial filtering.  For me (and many others) that causes unacceptable damage to star shapes and star colours.

Mark

[Craig123]

10 hours ago, sharkmelley said:

Look at my website (in my signature) and you'll find details of all my shots.  Are you using an A7 or an A7S - you've mentioned both.  There's a big difference between them. The A7S is the king of low-light cameras and is well suited to slow scopes because of its very low read noise and well controlled thermal noise.

The reason I use 30sec exposures is because for longer exposures I would need bulb mode and bulb mode invokes the "star eater" spatial filtering.  For me (and many others) that causes unacceptable damage to star shapes and star colours.

Mark

Great stuff Mark..had a look at your website.I have the A7s but so far my one imaging session for a few hours with an Atik 314l mono has yielded better results than a whole night of 2min  A7s subs..i think partly because my scope is f7.Having had the A7s a couple of years Id love to get it to work for me along the lines you have done  but not sure it's possible going to 30 secs.Just after I bought the camera I read your star eater articles and  was a little sad to say the least !

[Craig123]

On 30/11/2017 at 02:26, sharkmelley said:

Look at my website (in my signature) and you'll find details of all my shots.  Are you using an A7 or an A7S - you've mentioned both.  There's a big difference between them. The A7S is the king of low-light cameras and is well suited to slow scopes because of its very low read noise and well controlled thermal noise.

The reason I use 30sec exposures is because for longer exposures I would need bulb mode and bulb mode invokes the "star eater" spatial filtering.  For me (and many others) that causes unacceptable damage to star shapes and star colours.

Mark

Hi Mark..i can't stop thinking about trying to get my sony A7s to work for tracked astrophotography in someway. I got further forward with my Atik ccd over the last few weeks but wondered about putting a canon lens on the sony as you suggested.This morning i saw some more great shots with a modded Sony A7s using a canon 70-200.The thing that confuses me is these were 3 minute subs stacked with no sign ( to me ) of star eater. I  follow Fritz Helmut hemmerich on fb who does great work with a central ds modded Sony A7s.He says his camera has no sign of star eater.How do these astro modded cameras appear to be free of this.Still puzzled and frustrated at my Sony.

thanks

Craig

[sharkmelley]

13 hours ago, Craig123 said:

Hi Mark..i can't stop thinking about trying to get my sony A7s to work for tracked astrophotography in someway. I got further forward with my Atik ccd over the last few weeks but wondered about putting a canon lens on the sony as you suggested.This morning i saw some more great shots with a modded Sony A7s using a canon 70-200.The thing that confuses me is these were 3 minute subs stacked with no sign ( to me ) of star eater. I  follow Fritz Helmut hemmerich on fb who does great work with a central ds modded Sony A7s.He says his camera has no sign of star eater.How do these astro modded cameras appear to be free of this.Still puzzled and frustrated at my Sony.

thanks

Craig

I have seen some of the work that Fritz produces and it's top notch stuff. 

There are many reasons why the star-eating may not be apparent but I can assure you that the "star eater" spatial filtering is definitely taking place on A7S blub-mode exposures, whether or not it is obvious in the final image.  Astro-modding makes no difference to this. Some of the reasons why it may not be immediately obvious are the following:

• Long focal length.  A long focal length (e.g. 1200mm or more on the A7S) will make the stars large enough not to be eaten
• Image scale.  How many people displaying their images at 100% scale?  If you display an image at 50% scale or smaller you won't see the star destruction
• Star trailing.  Very small amounts of star trailing e.g. just one or two pixels of elongation, will be enough to protect stars from being eaten by enlarging their size
• Optics.  How many people use optics that are sharp enough to shrink stars into a 2x2 or 3x3 area?
• Stacking.  If you stack many dithered images together then the interpolations performed in aligning frames will tend to disguise the effects (unless you are using Bayer Drizzle).

Here's an example of an A7S stacked image using sharp Tak Epsilon optics at 500mm focal length.  Bulb mode was used in order to force star eating.  I processed the data using Bayer Drizzle at 200% in order to preserve as much fine detail as possible.   Unfortunately it also perfectly preserves the holes in the stars - take a look at this crop of the image:

I use very sharp optics at a 500mm focal length and I like to display my images at 100% scale (or sometimes 150% or 200% if I'm using drizzle).  That's the reason I find the star-eater spatial filtering to be totally unacceptable.  So it forces me to avoid shooting in bulb mode.  Other folk's mileage may vary, depending very much on the factors I describe above.

Mark

 

[Craig123]

18 hours ago, sharkmelley said:

I have seen some of the work that Fritz produces and it's top notch stuff. 

There are many reasons why the star-eating may not be apparent but I can assure you that the "star eater" spatial filtering is definitely taking place on A7S blub-mode exposures, whether or not it is obvious in the final image.  Astro-modding makes no difference to this. Some of the reasons why it may not be immediately obvious are the following:

• Long focal length.  A long focal length (e.g. 1200mm or more on the A7S) will make the stars large enough not to be eaten
• Image scale.  How many people displaying their images at 100% scale?  If you display an image at 50% scale or smaller you won't see the star destruction
• Star trailing.  Very small amounts of star trailing e.g. just one or two pixels of elongation, will be enough to protect stars from being eaten by enlarging their size
• Optics.  How many people use optics that are sharp enough to shrink stars into a 2x2 or 3x3 area?
• Stacking.  If you stack many dithered images together then the interpolations performed in aligning frames will tend to disguise the effects (unless you are using Bayer Drizzle)

I use very sharp optics at a 500mm focal length and I like to display my images at 100% scale (or sometimes 150% or 200% if I'm using drizzle).  That's the reason I find the star-eater spatial filtering to be totally unacceptable.  So it forces me to avoid shooting in bulb mode.  Other folk's mileage may vary, depending very much on the factors I describe above.

Mark

 

Thanks Mark , really appreciate the explanation.At this stage for me i would be pretty happy if i could get an image like the one you've used as an example of star eater !

The very first image i ever took using a tracker and my new (at the time) A7s had nothing notable on it but stars with holes which looked bad even for a total beginner.I think i could tolerate that if i could use dither but as my scope is not fast and i can't  find an adaptor for a reducer to fit the Sony on to my Skywatcher Ed80 i might have a look at a lens that would fit the camera. Are there any you would recommend that work well  with the A7s that i might get for a reasonable price s/h ? Also ,out of interest ,to you do the mod on a the A7s if i ever went down that route.

Many thanks

Craig

 

[sharkmelley]

6 hours ago, Craig123 said:

Thanks Mark , really appreciate the explanation.At this stage for me i would be pretty happy if i could get an image like the one you've used as an example of star eater !

The very first image i ever took using a tracker and my new (at the time) A7s had nothing notable on it but stars with holes which looked bad even for a total beginner.I think i could tolerate that if i could use dither but as my scope is not fast and i can't  find an adaptor for a reducer to fit the Sony on to my Skywatcher Ed80 i might have a look at a lens that would fit the camera. Are there any you would recommend that work well  with the A7s that i might get for a reasonable price s/h ? Also ,out of interest ,to you do the mod on a the A7s if i ever went down that route.

Many thanks

Craig

 

As far as adaptors go, I use a Canon lens adaptor on my A7S which means I can use standard Canon fittings on my scope.   I don't have any lens suggestions - I rarely use a lens.  I did a DIY mod on my A7S so I'm not sure of the best place to have it done professionally.

Mark

[Craig123]

8 hours ago, sharkmelley said:

As far as adaptors go, I use a Canon lens adaptor on my A7S which means I can use standard Canon fittings on my scope.   I don't have any lens suggestions - I rarely use a lens.  I did a DIY mod on my A7S so I'm not sure of the best place to have it done professionally.

Mark

ok. Thanks Mark

[Max N]

Hi Mark

I have been using a Sony A7s for a few years, but I have never settled on a totally satisfactory workflow. I have seen the amazing results you have achieved, and I don't think I am getting the best out of the camera. In a few months I will be able to in a position to spend a little bit of money on this hobby, but I want to make sure I am spending wisely. I'd be really grateful if you could give me a bit of guidance, and maybe a brief outline of your workflow?

I know you use PI, but do you use it for everything? Do you import the ARW files straight into PI or convert them first? All the Sony software for converting the ARW to TIFF or whatever seems to insist on doing some form of manipulation, even if just color balance.....

The camera is un-modified, but I am going to get it modded (probably the H-alpha mod by Life Pixel)

I usually take 30s subs at 2000-4000 iso

Scope is a Celestron Edge HD. Planning to get a shorter F/L refractor as well, around 450 to 500 F/L

At the moment I'm quite happy going for 'easy' targets like Andromeda, Whirlpool, Bodes. Will try for more extended targets when I have the other scope and modded camera.

My SQM is around 20.8 near zenith.

Any advice would be welcome.

 

[sharkmelley]

3 hours ago, Max N said:

Hi Mark

I have been using a Sony A7s for a few years, but I have never settled on a totally satisfactory workflow. I have seen the amazing results you have achieved, and I don't think I am getting the best out of the camera. In a few months I will be able to in a position to spend a little bit of money on this hobby, but I want to make sure I am spending wisely. I'd be really grateful if you could give me a bit of guidance, and maybe a brief outline of your workflow?

I know you use PI, but do you use it for everything? Do you import the ARW files straight into PI or convert them first? All the Sony software for converting the ARW to TIFF or whatever seems to insist on doing some form of manipulation, even if just color balance.....

The camera is un-modified, but I am going to get it modded (probably the H-alpha mod by Life Pixel)

I usually take 30s subs at 2000-4000 iso

Scope is a Celestron Edge HD. Planning to get a shorter F/L refractor as well, around 450 to 500 F/L

At the moment I'm quite happy going for 'easy' targets like Andromeda, Whirlpool, Bodes. Will try for more extended targets when I have the other scope and modded camera.

My SQM is around 20.8 near zenith.

Any advice would be welcome.

 

I use PI for calibration, stacking (often using Bayer drizzle), skyglow subtraction, white balance and stretching (using ArcsinhStretch).  The ARW raw files are used directly i.e. the lights, darks, flats and bias.  If they are converted using a raw file converter then the image data is in a non-linear colour space and that leads to all the kinds of problems that I documented in my (rather technical) critique of methodologies using Adobe's raw converter here:   http://www.markshelley.co.uk/Astronomy/Processing/ACR_Critique/acr_critique.html

I generally use DynamicBackgroundExtraction to subtract the skyglow.  But for really difficult gradients I export the (linear) stacked data into Photoshop and use various subtraction layers interactively before exporting back to PI for stretching.  Noise reduction is also something I still prefer to do in Photoshop - the noise reduction in the ACR filter is much easier to use than the options available in PI - mainly because it is completely interactive.

When using the Sony A7S on a long focal length scope like the Celestron Edge HD, the stars are well sampled so the Bulb mode "star eater" spatial filtering will cause no problems and you can afford to take long exposures.  At shorter focal lengths such as 500mm, the Bulb mode "star eater" starts to be a problem but it may or may not be an issue to you - different people have different tolerances for this.  The holes punched in stars are the biggest problem to me because Bayer Drizzle carefully preserves the holes!  So I never use Bulb mode for shooting.

Mark

 

[Max N]

Thanks Mark, that's exactly what I needed to know. I had a feeling I was losing information in the conversion, but the name 'raw converter' had me fooled into thinking I still had the raw data, just in a different file format. OK, I will buy a copy of PI soon when funds are available - I have already used up the trial period. I will also read your ACR article for background. BTW, thanks for making the arcsinhstretch available!

I have LR but not Photoshop, I will probably spring for the Photography CC subscription.

Thanks again

Max

[sharkmelley]

25 minutes ago, Max N said:

 I had a feeling I was losing information in the conversion, but the name 'raw converter' had me fooled into thinking I still had the raw data, just in a different file format.

Thanks for that really interesting comment.  It's quite possible that a lot of people understand it in the same way as you do.  In fact the raw converter takes the raw data (i.e. the camera sensor data) and completely transforms it into a standard colour space (e.g. sRGB or Adobe RGB) so that when it is displayed on the screen it appears as close as possible to the original scene.  In doing so it is performing camera specific transformations (since every camera is different) and more general transformations such as gamma.  In short, the values coming out of the raw converter are totally different to the data recorded by the sensor.

Mark

[Max N]

Yes, I think this misunderstanding has been holding me back for a while. A few years ago I started out with a modded Canon 600D and Nebulosity, and although there was quite a learning curve I did get some results I was happy with. But Nebulosity doesn't have native support for the Sony, and I couldn't find any import settings  that gave good results. I was floundering a bit, between using various raw converters and then taking Tiff files into Nebulosity, and trying to get to grips with PI. Anyway, I have a good direction now thanks to you. I will start working through some of the data I've collected with the Sony over the last couple of years.

[timwetherell]

On 07/05/2015 at 00:39, sharkmelley said:

I recently bought a brand new Sony A7S full frame mirrorless camera with the intention of finally replacing my ageing but trustworthy modified Canon 350D. The A7S is the camera famed for seeing the Milky Way in liveview.  Put a 50mm F1.8 lens on it and through the electronic viewfinder in liveview you'll see hundreds of stars invisible to the naked eye. A 1 second exposure makes the spiral arms of galaxies being to appear.

 

Thanks for this review. I'm contemplating getting a dslr for astroviewing/imaging and the Sony A7s is one of my options. This comprehensive and detailed review gives me a wealth of information! Especially coming from an astronomer's perspective (most reviews are for moody low light cinematography)  so thanks again for sharing

[timwetherell]

Looking at your video tour of the milky way (https://drive.google.com/file/d/0B3Ky5pyZvsINUWpobUZEeXVJeWc/view) Am I right in thinking that the A7s will live display integrated exposures? In other words, take a series of short exposures (say 1/2s) and feed them continuously one after another to the display on the back? I'm wondering about using this camera (or another like it) as a poor man's image intensifier eyepiece for pushing the observing envelope of my 7" a bit more into the deep sky side of things, so being able to do this would be very desirable in that role 

[sharkmelley]

The A7S doesn't have an option to display integrated exposures.  You would have to download them to a PC and use something like AstroToaster to do the live integration.  However, I've never tried it.

The way I made that video was to put the camera in Movie mode, turn the ISO up high and turn the video frame rate right down to 4 frames/sec.

 

Mark