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Enthusiast
Posts: 6
Registered: ‎06-14-2015
Message 1 of 46 (6,182 Views)

Star eater in bulb mode

Hi,

 

I am a new owner of A7R and I am an astrophotographr.  When I surf around the

internet and study about this camera, I found something that terrifies me.  Please

see this webpage:

Sony Star Eater - Real Life Test (kind of night horrors!)

 

It looks like the camera's internal image processing is removing some of the stars

in bulb exposure mode.  The above webpage is about A7, but there are A7S owners

who confirm the same problem.  Perhaps A7R is not an exception either.

 

This is not acceptable at all for astrophotography.  About 10 years ago, Nikon's DSLRs

were found to do the same thing to the raw files. This drove away astrophotographers

and contributed to Canon's 10 years of monopoly in astrophotography.

 

Please, Sony, don't make the same mistake that Nikon made 10 years ago.  Please

correct this via new firmware.  This is a fatal error for astrophotography.  A7R, A7S,

and the new A7RII are all very capable cameras.  I don't want to see their huge potential

being blocked by this.

Apprentice
Posts: 13
Registered: ‎06-16-2015
Message 2 of 46 (6,120 Views)

Re: Star eater in bulb mode

I have to agree about the annoyance of the star eater behaviour.  I bought the Sony A7S because of it's incredible low light performance - I thought it would be ideal for astrophotography.

 

Unfortunately astrophotography involves long exposures.  However, as soon as I used Bulb mode to take long exposures I found that the shape of my stars was being destroyed - they looked like rings because the bright centres had been removed - presumably by an internal noise reduction algorithm.  But all Noise Reduction was switched off using the camera menus.

 

Please provide some way of switching off this behaviour that is so destructive to images of starfields.

 

Mark

Apprentice
Posts: 13
Registered: ‎06-16-2015
Message 3 of 46 (6,081 Views)

Re: Star eater in bulb mode

 

Here's a crop from an actual image taken with the Sony A7S in Bulb mode.  Magnified by a factor of 2 so the pixels can be seen more easily

 

StarEaterExample.jpg

 

Note how a large number of stars have had their bright centres completely  punched out.  This was taken at a focal length of 500mm.  At short focal lengths, where the star occupies fewer pixels they end up being completely deleted.

 

Mark

Professional
Posts: 1,669
Registered: ‎01-08-2015
Message 4 of 46 (6,070 Views)

Re: Star eater in bulb mode

It seems to me that at least some of that must be attributable to the Bayer Filter.

 

The only choice I think I'd feel comfortable with for astrophotography, is the Leica M Monochrom. Either that or something with a Foveon sensor.

¹ The Lens is the Thing
² 'Full Frame' is the new 'Medium Format'
³ "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
Enthusiast
Posts: 6
Registered: ‎06-14-2015
Message 5 of 46 (6,066 Views)

Re: Star eater in bulb mode

[ Edited ]

Hi,

 

No.  It has nothing to do with the Bayer array.  It's very simple, the camera's internal processing (which cannot be turned off by users) tried to remove hot pixels from long-exposure images, and this removes part of the stars.  The same thing will happen even if the sensor is a monochromatic one.  Actually, stars will be sharper on monochromatic sensors, which make them look even more like hot pixels, and therefore even more likely to be removed by such algorithms.

 

Cheers,

Wei-Hao

 

Enthusiast
Posts: 9
Registered: ‎04-26-2015
Message 6 of 46 (5,933 Views)

Re: Star eater in bulb mode

This is terrible news for astrophotography and long exposure timelapse and implemented in a camera that doesn't need it either.  This was probably introduced by some bright spark copying Nikon, what an unnecessary feature !  Perhaps it wouldn't have been so bad if it could have been turned off but like so many other manufacturers they seem to know what we 'really' want.  What was long exposure NR for if not for that very thing !

 

Just like not having remote bulb mode in the API for a £2000 camera - what a joke.

 

Robert

Enthusiast
Posts: 6
Registered: ‎06-14-2015
Message 7 of 46 (5,831 Views)

Re: Star eater in bulb mode

This is another example, now from myself:

 

http://www.asiaa.sinica.edu.tw/~whwang/misc/star_eater.jpg

 

These are 200% crops from A7R images taken with Sigma 50/1.4A at F4.  One set is taken with 3min exposures in bulb mode, and the other with 30sec exposures (non-bulb).  You can see that many of the faint stars are completely going in the 3min exposures, and the cores of bright stars are also gone.  These are caused by Sony's hot pixel removal algorithm for long exposures.  Because of this, Sony cameras are completely NOT suitable for astrophotography.  (No one will like to deal with hundreds of 30sec exposures.  It's very inefficient on faint objects.)

 

Cheers,

Wei-Hao

Rookie
Posts: 1
Registered: ‎07-13-2015
Message 8 of 46 (5,820 Views)

Re: Star eater in bulb mode

I agree. Sony should address this issue ASAP.

 

I know for a fact that a very simple change to camera firmware will fix this problem.

 

thanks

 

Duncan

Enthusiast
Posts: 6
Registered: ‎07-10-2015
Message 9 of 46 (5,747 Views)

Re: Star eater in bulb mode

[ Edited ]

Can you try and shoot in Bracket.Cont -0.3EV mode if you have it.

This turns off the image processing in the camera for RAW images. (it was in another post I made a few days ago)

Also try a lower ISO - Most of my Astro images are down at ISO250

 

That seems to work OK for me, though I'm using a 5100L. The image processing in the camera gets right in the way of my Astroimaging - and needs to be removed. Such a shame as it's a great Camera on paper and under "normal" conditions.

 

Just a thought.

 

Ignore that - Your problem is WAY different to what I thought..... Good luck with it though.

Enthusiast
Posts: 6
Registered: ‎06-14-2015
Message 10 of 46 (5,430 Views)

Re: Star eater in bulb mode

Looks like the same exists on A7R2.

 

Sony, please correct this.

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