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Sony A7s - New Low-Light Camera - Wow!

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#51 Relativist

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Posted 18 May 2014 - 06:24 PM

So, depending on how well the A7s works for near live viewing, I would buy/make an optical train that would fully illuminate it if I were to buy the camera. The goal would be similar FOV to what the 1/2" chips give now, but more aperture.

#52 bwallan

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Posted 02 June 2014 - 09:17 PM

So, depending on how well the A7s works for near live viewing, I would buy/make an optical train that would fully illuminate it if I were to buy the camera. The goal would be similar FOV to what the 1/2" chips give now, but more aperture.


Most telescopes will illuminate a full frame sensor, at least all the ones I own do. You might get more vignetting with a full frame sensor as opposed to an APS-C size but a bit of flattening will recover most of the vignetted region.

As for a similar FOV you will require a scope with about 5x the focal length to yield the same FOV with a full frame sensor vs. a 1/2" (Mallincam Extreme) sensor. In this case your resolution would increase to 0.33 arcsec/pixel vs. 1.88 arcsec/pixel w/ the 1/2" sensor. This doesn't necessarily mean you'll see that resolution increase because sky conditions normally limit you to about 1-2 arcsec/pixel.

On the same scope the image resolution would be much the same since the sensor pixel sizes on the two cameras are the same size (A7S: 8.44x8.44 vs. 1/2": 8.4x9.8). The difference in image quality will be the difference between a captured video frame vs. a still image and the noise associated with each...

I am fairly sure the A7S will work for "near" live viewing (in video mode and/or still image mode) in much the same manner the Mallincam works in "near" live viewing. Whether the A7S will be worse, better than or about the same is still very much to be seen... Each camera will have its "fan-boys" and detractors as normal.

I, for one, am willing to bet on the A7S with my wallet and a pre-order. Up to about Nov. 2013 I was pretty much a solid Canon fan. The purchase of a Sony A7R, which took a lot of soul searching, has shown me there are other cameras that work at least as well, if not better! The A7S won't fit everyone's needs but it will (probably) fill a niche in my photographic requirements.

Clear skies!

bwa

#53 RandyC

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Posted 03 June 2014 - 11:55 AM

Hi bwa, thanks for the info. Increasing focal length to 5x current is simply not going to happen. Plus as you point out, seeing conditions won't support full resolution anyway. But it will get the most our of whatever telescope you have. Some simple cropping can eliminate the vignetting. It will be interesting how it's analog NTSC and digital video performance will compare. I wonder if the NTSC video covers the whole 1" sensor or is cropped within.

#54 bwallan

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Posted 03 June 2014 - 01:19 PM

It will be interesting how it's analog NTSC and digital video performance will compare. I wonder if the NTSC video covers the whole 1" sensor or is cropped within.


It will indeed be interesting to see how the A7S performs for astro-imaging (and potentially astro-video)!?

The image size off the A7S is 4240x2832; probably to allow 3:2 ratio images. Consumer Standard 4K video is 3840x2160, so there is a degree of cropping; 90.6%. However, I suspect the sensor size may have been designed to allow capture of Industry Standard 4096x2160 4K video as well? Too many 4K "standards"!

bwa

#55 Relativist

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Posted 03 June 2014 - 02:38 PM

Exciting times, I will be interested to see how it compares to the m43 cameras as well :-)

#56 bwallan

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Posted 03 June 2014 - 04:58 PM

...
Yes resolution can be increase by decreasing the pixel size in order to use more pixels within the sensor but the sensitivity will decrease for sure. There is no getting around this!!

Chris


I am the eternal optimistic... Somewhere down the road new sensor technology will overcome our current feeble efforts to capture every photon with "no" noise. Then we can all have sensors with 1 micron pixels! The best of resolution and sensitivity on one chip. But then we'll all have to be sitting in Earth orbit to get above that last lens in our telescopes, the atmosphere.

I currently have a 2.2 x 2.2 micron sensor in a planetary camera. Great resolution if there is lots of light hitting it (high signal-to-noise). Noisier than the devil in low light and/or long'ish exposures! But serves its specific purpose as a planetary/solar/lunar camera.

bwa

#57 coinboy1

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Posted 13 June 2014 - 12:20 AM

The Sony A7s looks promising, full frame, mirrorless, high sensitivity, small and lightweight. I really think this has some potential for video assisted astronomy. I am extremley curious how this would do with a video record at ISO 409,700 with a telescope!!! I have seen some of the videos on you tube in near total darkness and it is certainly impressive!

http://www.youtube.c...h?v=XgbUgNiHfXM

#58 GJJim

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Posted 13 June 2014 - 01:09 AM

I am the eternal optimistic... Somewhere down the road new sensor technology will overcome our current feeble efforts to capture every photon with "no" noise.


That technology is available now, but few of us can afford it. :grin:
http://www.emccd.com/what_is_emccd/

#59 RandyC

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Posted 13 June 2014 - 07:34 AM

The EMCCDs are noisy. I've only seen astrophotography done through intense stacking. Typically, thousands of short exposure stacks to make up an image. Live video is not done.

#60 GJJim

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Posted 13 June 2014 - 08:30 AM

The EMCCDs are noisy.


Noisy compared to? The astro-vid cams I've seen won't win any dynamic range contests.

I've only seen astrophotography done through intense stacking. Typically, thousands of short exposure stacks to make up an image. Live video is not done.


EMCCD can do 120 frames per second, stack four per and display at 30/sec - that's not a "video" rate?

#61 Relativist

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Posted 13 June 2014 - 09:14 AM

From what I head pre-orders are to arrive in July for the a7s, has anyone heard differently, hopefully sooner?

#62 DonBoy

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Posted 13 June 2014 - 11:18 AM

For those interested in EMCCD here is some info gleaned from Yahoo VideoAstro Group in reference to Stan Moore's post.


Celestron 8" f/10 EdgeHD

Photometrics 1k EMCCD

125ms (8FPS)

http://www.stanmoore...39856x125ms.JPG

http://www.stanmoore...22656x125ms.JPG

Stan Moore's website:

http://www.stanmooreastro.com/

#63 jdbastro

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Posted 13 June 2014 - 11:42 AM

From what I head pre-orders are to arrive in July for the a7s, has anyone heard differently, hopefully sooner?


Expected availability from B&H Photo is July 1st.

#64 RandyC

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Posted 13 June 2014 - 01:00 PM

EMCCD can do 120 frames per second, stack four per and display at 30/sec - that's not a "video" rate?


A four frame stack is not anywhere close to what you need for a reasonable live display using EMCCD. Don't get me wrong, Stan Moore shows it's beautiful long exposure imaging technology. The resolution possible is astounding. But it's simply not for video. In fact, I don't think the exposure times are shortened much over typical CCD imaging.

#65 GJJim

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Posted 13 June 2014 - 01:34 PM

EMCCD: 4 - second exposure

#66 RandyC

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Posted 13 June 2014 - 03:33 PM

Hi, That's a bright planetary nebula and I don't know your scope's aperture. I am not sure what a CCD exposure takes on a pn. Based on Stan Moore's work on galaxies, his exposure times are on par with CCD imaging.

#67 Moromete

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Posted 14 June 2014 - 05:04 AM

Gentlemen, it seems that the new A7S will be a Godzilla of DSLRs in respect of high ISOs according to this post http://www.dpreview..../thread/3685321 .

If you understand Spanish than have a look here too http://www.youtube.c...h?v=nJIZFVop7hA

So, prepare yourself to empty your pockets in July! :band:

#68 dag55

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Posted 14 June 2014 - 09:46 AM

Check amazon there is some A7s coming available July I used like new $1312
Dane

#69 Moromete

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Posted 14 June 2014 - 10:10 AM

I have a question: if one wants to sell his used Sony A7(A7R, A7S) how does the buyer know how many shutter actuations does the A7 have?

With Canon Dslrs you can check the number of shutter actuations with MagicLantern.

#70 JMKarian

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Posted 15 June 2014 - 07:01 PM

Michael Reichmann of Luminous Landscapes presents a nice review of the camera in context of the marketplace

Sony A7s First Impressions

#71 Relativist

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Posted 15 June 2014 - 11:36 PM

Nice read thanks! I'm hopeful that if the astro performance pans out we could get some custom astro software for it. We'll see.

#72 bwallan

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Posted 16 June 2014 - 01:40 PM

... custom astro software...


What are you looking for? A lot already exists... Everything that works for the A7/A7R should work for the A7S.

bwa

#73 Relativist

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Posted 16 June 2014 - 07:26 PM

... custom astro software...


What are you looking for? A lot already exists... Everything that works for the A7/A7R should work for the A7S.

Thanks, I was unaware of this, I'll do a search for what's available for the other A7 cameras.

bwa



#74 Moromete

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Posted 17 June 2014 - 03:30 AM

... custom astro software...


What are you looking for? A lot already exists... Everything that works for the A7/A7R should work for the A7S.

bwa


Can you tell us what astro software works already with the Sony A7/A7R which also allows long exposures in Bulb mode?

#75 Chris A

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Posted 17 June 2014 - 11:32 AM

What I am waiting to see is if this new Sony A7S will need to remove the stock filter and use just a UV/IR filter for detecting Ha emission nebulas or is the ISO good enough on really high amounts to pull this nebula through the stock filter. If it needs to be modified then I cannot see many doing this to a full frame expensive camera.

Chris A
Astrogate






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