Jump to content


Photo

Sony A7s - New Low-Light Camera - Wow!

  • Please log in to reply
623 replies to this topic

#351 Moromete

Moromete

    Viking 1

  • *****
  • Posts: 684
  • Joined: 15 Feb 2012
  • Loc: Romania

Posted 23 August 2014 - 09:32 AM

Allan, thank you for providing so much valuable information about A7S!

 

My calculations based on Sensorgen.info data show that A7S is 4x more light sensitive (per pixel area) than Canon 6D due to bigger pixels (8.3 vs y.5) and an increase of 17% on QE (50% vs 67%). In respect of noise at high ISOs I think the A7S has a similar degree of noise at ISO12800 (similar to Nikon D3S) as Canon 6D at ISO6400. 

I don't know if there any H-alpha senstivity difference between A7S and 6D, both stock/ unmodded.

 

Considering the price and performance differences do you think the A7S is worth the extra money than a Canon 6D?



#352 RandyC

RandyC

    Messenger

  • *****
  • Posts: 440
  • Joined: 01 Apr 2013
  • Loc: RI

Posted 23 August 2014 - 02:21 PM

 

Video exposures are only a max of 0.5sec. You are better off using standard 12Mp resolution and outputting to a computer monitor. That way you can lengthen the exposures to a minute or two. I still am not sure if the camera will work on DSOs with simple short single exposures. 

Not too sure what you mean by "I still am not sure if the camera will work on DSOs with simple short single exposures."  It definitely works or you couldn't take multiple subs for stacking.  As to the quality of individual subs, this is a personal call.  Personally I would not be happy with individual subs (as an end product) but they're far better than those I ever got off a Mallicam Xtreme but I'm talking about 30sec exposures not 5-7 sec.

 

bwa

 

Brian, Sony really hit a homerun with the A7S, seems it's been selling like hotcakes. Are you more satisfied with a single 30sec exposure on the A7S vs. say the A7R?



#353 tim53

tim53

    Cosmos

  • *****
  • Posts: 9486
  • Joined: 17 Dec 2004
  • Loc: Highland Park, CA

Posted 24 August 2014 - 11:20 AM

 

 

Video exposures are only a max of 0.5sec. You are better off using standard 12Mp resolution and outputting to a computer monitor. That way you can lengthen the exposures to a minute or two. I still am not sure if the camera will work on DSOs with simple short single exposures. 

Not too sure what you mean by "I still am not sure if the camera will work on DSOs with simple short single exposures."  It definitely works or you couldn't take multiple subs for stacking.  As to the quality of individual subs, this is a personal call.  Personally I would not be happy with individual subs (as an end product) but they're far better than those I ever got off a Mallicam Xtreme but I'm talking about 30sec exposures not 5-7 sec.

 

bwa

 

Brian, Sony really hit a homerun with the A7S, seems it's been selling like hotcakes. Are you more satisfied with a single 30sec exposure on the A7S vs. say the A7R?

 

If the camera can shoot in "continuous" mode, I see no reason you couldn't take longer exposure "video" frames by assembling these shots into a video that could be aligned and stacked as such. 



#354 Relativist

Relativist

    Skylab

  • *****
  • Posts: 4301
  • Joined: 11 Oct 2003
  • Loc: OC, CA, USA

Posted 24 August 2014 - 07:19 PM

Isn't that what deep sky stacker, and the real time observer add on do? The question has been support for A7 raw files I believe.

#355 bwallan

bwallan

    Mariner 2

  • -----
  • Posts: 222
  • Joined: 08 Jul 2010
  • Loc: Alberta, Canada

Posted 24 August 2014 - 10:09 PM

 

 

Video exposures are only a max of 0.5sec. You are better off using standard 12Mp resolution and outputting to a computer monitor. That way you can lengthen the exposures to a minute or two. I still am not sure if the camera will work on DSOs with simple short single exposures. 

Not too sure what you mean by "I still am not sure if the camera will work on DSOs with simple short single exposures."  It definitely works or you couldn't take multiple subs for stacking.  As to the quality of individual subs, this is a personal call.  Personally I would not be happy with individual subs (as an end product) but they're far better than those I ever got off a Mallicam Xtreme but I'm talking about 30sec exposures not 5-7 sec.

 

bwa

 

Brian, Sony really hit a homerun with the A7S, seems it's been selling like hotcakes. Are you more satisfied with a single 30sec exposure on the A7S vs. say the A7R?

 

Very happy with 30sec exposures at up to ISO12800, even up to ISO25600; probably about the same noise level as A7R 30sec exposures at ISO3200.  And 30sec exposures off the A7S at ISO3200 are pretty much noise free!  So you could probably do 7.5sec exposures at ISO12800 and get about the same thing as A7R 30sec exposures at ISO3200.

 

bwa



#356 bwallan

bwallan

    Mariner 2

  • -----
  • Posts: 222
  • Joined: 08 Jul 2010
  • Loc: Alberta, Canada

Posted 25 August 2014 - 12:00 AM

Allan, thank you for providing so much valuable information about A7S!

 

My calculations based on Sensorgen.info data show that A7S is 4x more light sensitive (per pixel area) than Canon 6D due to bigger pixels (8.3 vs y.5) and an increase of 17% on QE (50% vs 67%). In respect of noise at high ISOs I think the A7S has a similar degree of noise at ISO12800 (similar to Nikon D3S) as Canon 6D at ISO6400. 

I don't know if there any H-alpha senstivity difference between A7S and 6D, both stock/ unmodded.

 

Considering the price and performance differences do you think the A7S is worth the extra money than a Canon 6D?

I purchased the A7S because I was very happy with Sony's A7R for astrophotography, and I am very pleased with the A7S's performance.  Up to that time I had been a Canon fan-boy for years...

 

I know a couple of people with modded Canon 6D's and they are very happy with their 6D's.  The 6D has also had some good astro reviews by some fairly knowledgeable users.  The 6D's is also well supported by astrophotography software.  The Sony A7 series is not supported at all in this area :(.  Since I seldom use camera control software this doesn't really bother me.  I'm quite happy with a wired timer-remote or TriggerTrap.  In fact the Time-Lapse Camera App on both the A7R and A7S is quite adequate for most of the astro-imaging subs I shoot even though it does not support exposures beyond 30sec.

 

Hard call on which is the best regardless of the money difference?  I like the A7S, other people like the 6D...

 

bwa



#357 RandyC

RandyC

    Messenger

  • *****
  • Posts: 440
  • Joined: 01 Apr 2013
  • Loc: RI

Posted 25 August 2014 - 08:31 AM

How do you think Sony A7S compares to my Xtreme exposures, like NGC6946: https://www.flickr.c...th/15019218802/

 

NGC6946 was using Xtreme at 200sec exposure in a C11, with Galaxy Contrast Enhancement filter. I also quite a bit of video processing equipment shown here: https://www.flickr.c...ns/14353883006/

 

Finally, I give it a quick post process touchup using Autocorrect in Fotor software. Do you think A7S would be even better <200sec.



#358 bwallan

bwallan

    Mariner 2

  • -----
  • Posts: 222
  • Joined: 08 Jul 2010
  • Loc: Alberta, Canada

Posted 25 August 2014 - 08:57 PM

How do you think Sony A7S compares to my Xtreme exposures, like NGC6946: https://www.flickr.c...th/15019218802/

 

NGC6946 was using Xtreme at 200sec exposure in a C11, with Galaxy Contrast Enhancement filter. I also quite a bit of video processing equipment shown here: https://www.flickr.c...ns/14353883006/

 

Finally, I give it a quick post process touchup using Autocorrect in Fotor software. Do you think A7S would be even better <200sec.

Randy,

 

I don't mean to be cruel but your Mallincam Xtreme images (very similar to mine) are the primary reason I sold my Mallicam equipment.  I simply could not live with the image quality, in particular the totally destroyed stars!  Stars have color/character...  They definitely are not bright white blown out spots with black donuts!!  And I beat on Rock Mallin for a solution to this problem to no avail.  With the hyper circuitry (high gain) of the Xtreme required to capture faint astro stuff there was simply not enough dynamic range available to do justice to bright objects in the same image.  You got one or the other but not both!  Of course you could shoot Xtreme video at different exposures or gains and combine them using high dynamic gain software but this defeated the real goal of the Xtreme to output targets in a "real time" video format, which it is quite good at.

 

As far as images off the Sony A7S, or for that matter the A7R, there is no comparison.  A single sub off either camera will produce what I consider to be an "astro-image" BUT not that great a quality from one sub.  Signal-to-noise goes up as the SqRt of the number of subs.  One sub at say 30sec & ISO 3200-6400 is going to look pretty decent w/ internal high ISO noise reduction.  A sub at 60sec & ISO1600-3200 is going to look a lot better and a sub at 180sec & ISO800-1200 is going to look even better.  A combination of long exposure and high ISO is probably just going to be blown out by normal sky glow, so something like 200sec @ ISO 6400 is not going to yield much of value unless you're using a really slow scope/lens, i.e.: f/20+/-.  I find 30sec @ ISO 12800 results in a blown out sky but 10sec @ ISO 12800 can result in a usable sub.

 

Summing up.  I personally don't like the image quality off the Mallincam Xtreme or from single subs off the A7S or A7R.  I believe the only way to generate good quality astro-images is to collect as many subs of your target as possible then align, stack and process them into a high quality final image.  However, if you're into astro-video, go for it!  If you're happy with the quality of a single sub off any camera, go for it!

 

Just my thoughts...

 

bwa



#359 mclewis1

mclewis1

    Thread Killer

  • ****-
  • Posts: 11073
  • Joined: 25 Feb 2006
  • Loc: New Brunswick, Canada

Posted 26 August 2014 - 08:03 AM

And therein lies the issue ... the fundamental difference between viewing (EAA) and creating pretty pictures (imaging). There is certainly cross over between the two disciplines, they aren't mutually exclusive but when you concentrate on capabilities to maximize one you generally diminish the capabilities for the other.

 

I still don't see how the A7/A7S as it's being presented here demonstrates any real EAA capabilities. A very capable camera to be sure, but the way it's being presented here it's being used as an imaging camera similar to how most folks use a DSLR. :shrug:



#360 David B in NM

David B in NM

    Messenger

  • *****
  • Posts: 430
  • Joined: 05 Sep 2010

Posted 26 August 2014 - 08:20 AM

Mark,

 

Perhaps you missed this link that was provided in a previous post to this thread.  It illustrates the camera is quite capable for EAA purposes too.

 

https://www.youtube....h?v=UUzLJ-M2Z_I

 

David B in NM



#361 RandyC

RandyC

    Messenger

  • *****
  • Posts: 440
  • Joined: 01 Apr 2013
  • Loc: RI

Posted 26 August 2014 - 09:53 AM

Mark,

 

Perhaps you missed this link that was provided in a previous post to this thread.  It illustrates the camera is quite capable for EAA purposes too.

 

https://www.youtube....h?v=UUzLJ-M2Z_I

 

David B in NM

I don't think the above video does the A7S justice. Those are 0.5second exposures. The word video is used in short exposure astronomy because the pixels in NTSC/PAL video are large, and hence the cameras are fast. In my mind, EAA is anything under about 3 minuutes total. I do not believe in manual stacking because it is too complex for the casual observer.

 

I have always had a pet peeve for technical boondoggles that scare people away from astronomy... ie 20hour exposures on a $30k 10inch scope.

 

If the A7S has an internal 4stack NR feature that is acceptable, as long as its reasonable simple to use. The procedures should allow casual observers to move around the sky and enjoy the tour.

 

If I can get <300sec exposures that are better than what I currently have, I am definitely interested. But I want detail of the object itself, not the overall background and stars.

 

All that said, I'm definitely getting the A7S because from everything I've heard, Sony broke down the barriers with this one. It's just a matter of when.


Edited by RandyC, 26 August 2014 - 09:55 AM.


#362 chasing photons

chasing photons

    Vostok 1

  • -----
  • Posts: 167
  • Joined: 19 Mar 2013
  • Loc: Minnesota

Posted 26 August 2014 - 10:17 AM

The Sony A7S clearly has the capabilities for EAA with nice examples (too few so far) of sub 30 second exposures at higher ISOs with little noise.  Unfortunately, the majority of the early users of the A7S are using it for imaging (one extreme), or live astro video at 4fps (the other, noisy extreme).  I would be perfectly happy with its performance in the sub 30 second single exposure range if not for the following negatives. 

 

The negatives I see so far are the large, full frame sensor that begs for an expensive, fast OTA with a large image circle that is not focal reducer friendly, the $2500 price tag, and the current lack of comprehensive remote control/viewing APPs or software to create a nice clean system where you can sit back and enjoy 15 – 30 second exposures on your tablet or laptop screen.

 

I am not going to lay down $5K ++ for a complete EAA system until it meets my requirements.  The bits and pieces of the puzzle are getting close, and that is why I am here, to learn about the capabilities, and limitations, of each piece.  Maybe in a year or two that system will be available.  Whether it will include a dedicated astro CCD camera, or an off the shelf dslr/mirrorless camera, I really couldn’t say at this point.  But until then, I will gladly sit on the sidelines until the various technologies (OTA, mount, camera and software) mature and work seamlessly together.  Yep, I know, I am a cheap, odd duck that will only be happy with something really good.



#363 RandyC

RandyC

    Messenger

  • *****
  • Posts: 440
  • Joined: 01 Apr 2013
  • Loc: RI

Posted 26 August 2014 - 10:21 AM

The Sony A7S clearly has the capabilities for EAA with nice examples (too few so far) of sub 30 second exposures at higher ISOs with little noise.  Unfortunately, the majority of the early users of the A7S are using it for imaging (one extreme), or live astro video at 4fps (the other, noisy extreme).  I would be perfectly happy with its performance in the sub 30 second single exposure range if not for the following negatives. 

 

The negatives I see so far are the large, full frame sensor that begs for an expensive, fast OTA with a large image circle that is not focal reducer friendly, the $2500 price tag, and the current lack of comprehensive remote control/viewing APPs or software to create a nice clean system where you can sit back and enjoy 15 – 30 second exposures on your tablet or laptop screen.

 

I am not going to lay down $5K ++ for a complete EAA system until it meets my requirements.  The bits and pieces of the puzzle are getting close, and that is why I am here, to learn about the capabilities, and limitations, of each piece.  Maybe in a year or two that system will be available.  Whether it will include a dedicated astro CCD camera, or an off the shelf dslr/mirrorless camera, I really couldn’t say at this point.  But until then, I will gladly sit on the sidelines until the various technologies (OTA, mount, camera and software) mature and work seamlessly together.  Yep, I know, I am a cheap, odd duck that will only be happy with something really good.

I don't know maybe I'll wait until I see a 2-3 minute exposure with with full NR on. 



#364 RandyC

RandyC

    Messenger

  • *****
  • Posts: 440
  • Joined: 01 Apr 2013
  • Loc: RI

Posted 09 September 2014 - 07:14 AM

Some of you may have noticed the dpreview comparing the Sony A7S, A7R and Canon EOS5D. The Canon is quite a bit less expensive. Based on comparing its low light performance using this chart, the A7S is better. There is more detail at ISO 25,600 that would be usable with or without noise reduction. Sony simply wrings more detail out of its pixels.

 

http://www.dpreview....anon-eos-5d-iii

Attached Files

  • Attached File  A7s.jpg   176.79KB   8 downloads


#365 bwallan

bwallan

    Mariner 2

  • -----
  • Posts: 222
  • Joined: 08 Jul 2010
  • Loc: Alberta, Canada

Posted 09 September 2014 - 03:19 PM

Some of you may have noticed the dpreview comparing the Sony A7S, A7R and Canon EOS5D. The Canon is quite a bit less expensive. Based on comparing its low light performance using this chart, the A7S is better. There is more detail at ISO 25,600 that would be usable with or without noise reduction. Sony simply wrings more detail out of its pixels.

 

http://www.dpreview....anon-eos-5d-iii

I'd read this review a while back but it was good to review the results after having used both the A7R and A7S for a time...

 

Daylight photography doesn't have to worry about the number of photons collected per sensor pixel to generate an image, i.e.: there are lots of them.

 

Astrophotography and nightscape photography, on the other hand, has to collect enough photons per pixel to actually generate something above the inherent noise of the system to generate an acceptable end result.  This normally means longer exposures which is the ONLY way to collect more photons from faint targets.  What we are discussing in this comparison is the handling of those few photons.

 

The comparison shows the A7S and A7R producing about the same level of image quality up to the max. ISO of the A7R (when the A7R image is reduced to 12 MPixels); however, I do note the resolution of the A7R image is considerably better than that off the A7S, and I have found this in practice.  As a result I normally use the A7S on lenses/scopes above 500mm focal length and the A7R on wider angled lenses/scopes to retain as much resolution as possible.

 

The difference between the Sony A7 series and Canon images is entirely due to inherent noise and the differences in handling this, either by "cleaner" sensor technology (pixel size, etc.) or by proprietary hardware/software processing algorithms.  At the moment Sony appears to be the winner in this race...  How long? Until the next Canon or Nikon technology hits the market??  Or some other camera manufacturer plays a game of technology leapfrog to gain a short term advantage?

 

Personally I'm not happy with a single high ISO image (sub) off ANY camera!  Sure they show something but is it really an "image" worth saving and getting excited about!?  Not in my opinion.  Now, if you collect a whole bunch more photons to fill in all the blanks/holes in a high ISO image by shooting, aligning and stacking a number of subs (the more the better), thus improving the signal-to-noise ratio, I can see the usefulness of a high ISO, low noise camera.  And I have processed stacked astro-images with 30-50x30sec exposures at anywhere up to ISO102400 and they can be quite nice; however, 30sec subs @ ISO6400 (maybe ISO12800) is about all my sky conditions normally allow using an f/8.0 lens/scope before totally blowing out the subs (and considerably less exposure and/or lower ISO with an f/2.0 lens!).  30sec subs at ISO3200 are normally more than adequate (and cleaner from the get-go).  And 60sec subs @ ISO1600-3200 are wonderful, not really due to the lower ISO but very much due to collecting double the number of photons per sub; essentially improving the signal-to-noise ratio right at the point of origin, i.e.: the initial sub.

 

But as I've said (a few times previously), if you're happy with single astro-images off any camera, go for it!

 

bwa



#366 RandyC

RandyC

    Messenger

  • *****
  • Posts: 440
  • Joined: 01 Apr 2013
  • Loc: RI

Posted 09 September 2014 - 03:44 PM

Sony has done so much work over the years in many areas besides photography. Their analog video equipment in XV-C900 and XV-C700 color correctors, Detail Enhancers and of course TVs and consumer electronics.  But perhaps, where they really get their edge is video games. The PlayStation technology is creating the photons themselves. Video game buffs using video enhancers, especially those designed for vintage games are some of the best.

 

I think traditional camera manufacturers will have some catching up to do.



#367 chasing photons

chasing photons

    Vostok 1

  • -----
  • Posts: 167
  • Joined: 19 Mar 2013
  • Loc: Minnesota

Posted 09 September 2014 - 08:29 PM

 

But as I've said (a few times previously), if you're happy with single astro-images off any camera, go for it!

 

bwa

 

 

 

That is almost the definition of Electrically Assisted Astronomy or near real time observing.  Short, single exposures or several short subs automatically aligned and stacked, either in camera or with additional software, is what interests many people in this particular forum. 

 

I would prefer short exposures in order to eliminate the need for guiding.  I don't know how many times I have watched NSN only to see even the seasoned broadcasters with fairly high end equipment have unexpected trouble with polar alignment and guiding.  Of course, if stacking 3 or 4 short subs to improve the signal to noise ratio, without a high quality tracking mount or guiding, auto aligning the stacked images is of prime importance.

 

Can anyone tell me if the Sony A7S can auto align images (and do a good job of it) when it performs HDR and noise reduction functions using multiple images?



#368 bwallan

bwallan

    Mariner 2

  • -----
  • Posts: 222
  • Joined: 08 Jul 2010
  • Loc: Alberta, Canada

Posted 09 September 2014 - 10:20 PM

 

 

But as I've said (a few times previously), if you're happy with single astro-images off any camera, go for it!

 

bwa

 

 

 

That is almost the definition of Electrically Assisted Astronomy or near real time observing.  Short, single exposures or several short subs automatically aligned and stacked, either in camera or with additional software, is what interests many people in this particular forum. 

 

I would prefer short exposures in order to eliminate the need for guiding.  I don't know how many times I have watched NSN only to see even the seasoned broadcasters with fairly high end equipment have unexpected trouble with polar alignment and guiding.  Of course, if stacking 3 or 4 short subs to improve the signal to noise ratio, without a high quality tracking mount or guiding, auto aligning the stacked images is of prime importance.

 

Can anyone tell me if the Sony A7S can auto align images (and do a good job of it) when it performs HDR and noise reduction functions using multiple images?

 

1st off both Auto HDR and Multi-Frame Noise Reduction (MFNR) are ONLY available in JPG mode, i.e.: if RAW (or RAW+JPG) is selected, neither is selectable!

Same applies to A7S Silent Shooting Mode, neither of the above is selectable and High ISO Noise Reduction is also not selectable.

 

Auto HDR captures three JPG's and MFNR captures four JPG's for internal processing.

 

Both the Auto HDR and MFNR tools align the multiple images captured (or at least really try to align them).  I haven't had a case where either tool has failed to properly align captured images.  MFNR  uses the astronomical technique of averaging several shots together; random noise gets averaged out while the pixels consistent from shot-to-shot get reinforced, i.e.: the signal-to-noise ratio is improved, in the case of MFNR by a factor of 2x (sqrt of 4).  I'm not too sure if Auto HDR actually improves signal-to-noise or not.  HDR shoots hi, lo and set exposures with the intent of improving the dynamic range of the resulting image.  I guess in theory it should improve signal-to-noise as well, at least to some extent.  Where Auto HDR is handy is shooting targets with a wide dynamic range such as the Orion Nebula or a bright sunset:

 

Dawson%2BCity%2C%2BYukon%2BSunset.jpg

 

Clear skies!

 

bwa



#369 bwallan

bwallan

    Mariner 2

  • -----
  • Posts: 222
  • Joined: 08 Jul 2010
  • Loc: Alberta, Canada

Posted 09 September 2014 - 10:26 PM

And another Auto HDR sunset, this time a panorama of Auto HDR images off a Sony A7R:

Eagle%2BPlains%2C%2BYukon%2BSunset%2B2.j

 

bwa


Edited by bwallan, 09 September 2014 - 10:27 PM.


#370 Dom543

Dom543

    Mariner 2

  • *****
  • Posts: 278
  • Joined: 24 Oct 2011

Posted 10 September 2014 - 07:38 AM

Earlier this year a forum member HowieL made an interface for Deep Sky Stacker, that makes it more suitable for near-live observing. If the Sony A7s can take sequential images and download them into a directory, then using HowieL's interface, DSS can pick them up from there and stack them for instant viewing.

Here is the thread http://www.cloudynig...6545226/page...

It would be interesting to hear, if this can, in fact, be beneficially used with the A7s.

--Dom

#371 Relativist

Relativist

    Skylab

  • *****
  • Posts: 4301
  • Joined: 11 Oct 2003
  • Loc: OC, CA, USA

Posted 10 September 2014 - 02:17 PM

Dom, Thank you! I've been talking about this for a while, and at the end of the linked thread I asked Howie about the A7s.

http://www.cloudynig...deepskystacker/

The issue Howie brought up is compatibility with A7 raw files, then he asked for samples, which in several threads, including this one, I've been encouraging owners to contact Howie and provide.

#372 chasing photons

chasing photons

    Vostok 1

  • -----
  • Posts: 167
  • Joined: 19 Mar 2013
  • Loc: Minnesota

Posted 10 September 2014 - 07:08 PM

 

 

1st off both Auto HDR and Multi-Frame Noise Reduction (MFNR) are ONLY available in JPG mode, i.e.: if RAW (or RAW+JPG) is selected, neither is selectable!  Same applies to A7S Silent Shooting Mode, neither of the above is selectable and High ISO Noise Reduction is also not selectable.

 

Auto HDR captures three JPG's and MFNR captures four JPG's for internal processing.

 

Both the Auto HDR and MFNR tools align the multiple images captured (or at least really try to align them).  I haven't had a case where either tool has failed to properly align captured images.  MFNR  uses the astronomical technique of averaging several shots together; random noise gets averaged out while the pixels consistent from shot-to-shot get reinforced, i.e.: the signal-to-noise ratio is improved, in the case of MFNR by a factor of 2x (sqrt of 4).  I'm not too sure if Auto HDR actually improves signal-to-noise or not.  HDR shoots hi, lo and set exposures with the intent of improving the dynamic range of the resulting image.  I guess in theory it should improve signal-to-noise as well, at least to some extent.  Where Auto HDR is handy is shooting targets with a wide dynamic range such as the Orion Nebula or a bright sunset:

 

 

 

 

Thank you for the thorough description of the Auto HDR and MFNR modes in the Sony A7S.  Your examples of images with high dynamic range are very nice.



#373 RandyC

RandyC

    Messenger

  • *****
  • Posts: 440
  • Joined: 01 Apr 2013
  • Loc: RI

Posted 20 September 2014 - 11:47 PM

The icx418 and A7s pixel sizes are both approx the same at 8.4um. I suppose the readout on the a7s is just more complex to support the 10mp. Even with a sensor almost 3 times the size, the A7s is much more than 3x the resolution.

#374 mclewis1

mclewis1

    Thread Killer

  • ****-
  • Posts: 11073
  • Joined: 25 Feb 2006
  • Loc: New Brunswick, Canada

Posted 21 September 2014 - 10:59 AM

The 418/428/828 sensors are 1/2 format and measure about 8mm diagonally. The Sony A7 is a full frame (35mm) sensor. The Sony sensor is diagonally 5.37 times larger, not "almost 3 times". Measured in area it's about 30 mm² vs. 860 mm². ... that's why the mega pixel numbers differ so much.

 

There's really no magic in the sensor layout. With similar ~8.4um sized pixels the ratio in size between the different sensors (if we use the PAL 419/429/829 version with their 8.3-8.6um pixels) is going to be similar (there's not much difference in spacing between the pixels). So the actual resolution (ability to resolve fine lines) will be similar between the two sensors. It's the fov that so dramatically different with the A7 sensor.

 

 

I still don't understand why most of this thread hasn't taken place in the DSLR & digital camera imaging forum ... there doesn't seem to be much EAA viewing being done in the examples.



#375 ccs_hello

ccs_hello

    Fly Me to the Moon

  • *****
  • Posts: 6626
  • Joined: 03 Jul 2004

Posted 21 September 2014 - 12:59 PM

For RandyC

 

Area wise, a F.F. image sensor's area can fit 27.3 times type-1/2" sensors.

See "area normalized" column (1 vs. 0.0361)

http://www.cloudynig...e-sensor-sizes/

 

Re: sensor used in A7s

Other than its large pixel pitch, the sensor technologies of its generation of SONY Exmor

is a significantly improved CMOS Image sensor (low power, per-pixel sense amplifier a.k.a. active pixels, built-in column parallel A/D, and performs both analog CDS and digital domain CDS.)

In the end, the net effect is the overall image-level S/N is so high such that it can sustain extreme signal boost (ISO boost) without being complaint as "too noisy".

 

This is the main reason that even a type-1/2" CCD (ICX418, ICX828, etc.) has the similar per-pixel area as A7s, and even ICX418AK, ICX828AK have complementary-color Bayer filter (CMY +G) than A7s' RGBG (primary-color) which let in more lights, A7s' can still afford offering extreme ISO boost.

 

For Mark (re: why A7s)

 

I think in the forum we are all looking for a product that can "catch" extreme low light for astro viewing purposes.

It seems to me A7s has potentials due to its extremely high ISO capability.

On the other hand, I am also curious that if there is a good summary write up

describing how to use A7s in a way that has the appearance of (almost) continuously taking images (few second exp time) and displaying them without too much delay.

Even if its not directly, immediately off the camera body, can PC-tether do it?

 

Clear Skies!

 

ccs_hello








Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics