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Sony A7s - New Low-Light Camera - Wow!

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#451 chasing photons

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Posted 01 October 2014 - 10:49 AM

As I said before in this very thread...

 

Although the maximum 0.25 second exposure in video mode is truly impressive with the Sony A7S, I anxiously await more demonstrations of its capabilities in still mode with single exposures under 30 seconds and also with the noise reduction or wide dynamic range functions enabled depending on the target DSO. I want to see jpeg stills with any in camera processing that improves the output, not raw images.

Video is not required for near real time observing of DSOs so why cripple the Sony A7S output in this fashion? I think it will truly shine for stills under 30 seconds with OTAs in the f/4 to f/6 range with moderate apertures and moderate ISOs.

Ideally, I would like to use the Sony A7S via Wi-Fi with a tablet for both control of camera settings and display of the current still image. Alternatively, I would like to eventually control it with software like AstroLive, but that will be a LONG time coming, if ever, I am afraid.

Anyway, more technology like the Sony A7S is needed in this endeavor, and I am happy to see products like this develop and become popular. It can only help!

 

I am glad you agree...

 

Good point about why limit the A7s NRT viewing to just video mode? We are using multiple second exposures of 3-90s using existing Mallincam or AVS cameras so why not showcase what this A7s can do with 20,30 or 60s exposures??

Al

 

No one will see me use the "V" - word where it pertains to EAA unless I absolutely have to.  If someone wants to go directly to an analog monitor to display at 30fps what are essentially still images, many seconds in length, fine.
 
But I have no interest in that.  Give me a camera LIKE the Sony A7S and a means to easily (as close to automatic as I can get) transfer that wonderful short exposure still image to a tablet or laptop, complete with all of the internal or external automatic processing I can throw at it, and I will finally be a happy camper.  Things are moving in this direction with cameras and software and I will continue to cheer everyone involved that will eventually lead us to that ideal EAA system… or maybe I should say MY ideal EAA system.



#452 RandyC

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Posted 02 October 2014 - 01:57 PM

Brian, Have you tried the multi frame noise reduction MFNR function on astro images? Does it update the view as it's stacking the 4 frames. Is there a limit to being 30sec exposure? thanks.

 

http://www.dpreview....s/post/53898698



#453 bwallan

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Posted 02 October 2014 - 03:07 PM

Brian, Have you tried the multi frame noise reduction MFNR function on astro images? Does it update the view as it's stacking the 4 frames. Is there a limit to being 30sec exposure? thanks.

 

http://www.dpreview....s/post/53898698

See.  30sec is max.; not functional in Bulb mod.



#454 Moromete

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Posted 03 October 2014 - 06:14 AM

I have encountered a very serious problem with the colors of A7S when I took it to a circus a few days ago, the highlights having strong color fringes. Look at the colored lights here:  http://www.dpreview....m-post-54496056 .

 

Has any A7S owner experienced this problem? Is this problem present on the whole A7 line?

 

Do you know what can be done to obtain images without such artefacts with A7S?



#455 RandyC

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Posted 03 October 2014 - 07:35 AM

Is auto white balance on?



#456 Moromete

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Posted 03 October 2014 - 11:38 AM

Yes.

I went with my familly to the circus and I thought this would be a great opportunity to try the camera in very low light and mixed lighting also.

I used the following settings for all images taken at circus: JPEG Extra Fine, Auto WB, NR Low, Manual Mode, Auto ISO, AF-S, center AF point on Medium size, Sony FE 28-70mm kit lens, Creative Style Standard, Electronic Shutter, Mettering Multi, Picture Profiles Off.

No HDR was used.

I I don't remember if DRO was on Auto or Off unfortunatelly but I suppose it shouldn't make a big difference regarding the hallows around the bright light sources.

I also wonder if this problem could have a negative impact on star color during long exposures.

#457 chasing photons

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Posted 03 October 2014 - 12:32 PM

I have encountered a very serious problem with the colors of A7S when I took it to a circus a few days ago, the highlights having strong color fringes. Look at the colored lights here:  http://www.dpreview....m-post-54496056 .

 

Has any A7S owner experienced this problem? Is this problem present on the whole A7 line?

 

Do you know what can be done to obtain images without such artefacts with A7S?

 

 

This looks like suspended particles (dust, water droplets and smoke) in the air, illuminated by the various color lights.  You can see the colorful columns of scattered photons even in cases where the light source is pointed away from the camera.  In the photos where the lights are aimed towards the camera, the ‘halo’ around the light source appears to be photons deflected by particles between the camera and light source.  I would hardly consider a circus environment with animals and what not running around, and maybe even manufactured ‘smoke’ for ambiance, to be anywhere close to that of a clean room.  Think of how difficult it is to see a laser beam until smoke or other suspended particles are introduced.



#458 bwallan

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Posted 03 October 2014 - 12:55 PM

I have encountered a very serious problem with the colors of A7S when I took it to a circus a few days ago, the highlights having strong color fringes. Look at the colored lights here:  http://www.dpreview....m-post-54496056 .

 

Has any A7S owner experienced this problem? Is this problem present on the whole A7 line?

 

Do you know what can be done to obtain images without such artefacts with A7S?

First, I don't consider this a problem or an artifact.  The air is obviously foggy or smoky and under these conditions, shooting directly into lights, you're going to see halos.  Even the eye will see halos...

 

You can reduce the "problem" by shooting RAW and processing out the halos; a bit of work.  Or you can shoot internal HDR with a wide EV range.  Or you can capture HDR images and process them later; my preferred approach.

 

Another option is to set metering to center and always meter for the target you're shooting.  As you probably realize it is never a great idea to shoot directly into bright lights in a dark environment unless you want this effect.

 

The other option, shoot with a narrower lens and keep the light(s) out of the image.  Might be hard to do with the 28-70mm zoom but cropping works:

Moromete%2BCircus.jpg

 

I don't consider this a problem with the A7 series of cameras any more than what I would see with my Canon or Pentax cameras.  All would perform about the same under your imaging conditions.

 

As for "a negative impact on star color during long exposures", yes it will have an impact but no more so than with any other camera.  Keep your exposures and ISO reasonable, and shoot a range of subs so you can reconstitute stars in the final image.

 

Now, that we've reviewed a few of the options take a moment to realize how amazing this picture is considering it was shot at 1/200 sec at ISO 51200.  I don't know of ANY other camera that would come close!!  Even the A7R tops out at ISO 51200 and only when shooting in multi-frame noise reduction mode...

 

I do love the camel.  The pink fringe of hair around its ears and neck is classic, and focus is dead on.  In keeping with the title of this thread... WOW!

 

bwa 


Edited by bwallan, 03 October 2014 - 08:32 PM.


#459 claudius

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Posted 03 October 2014 - 01:37 PM

Hello Brian,

 

Which adapter are you using for prime focus astrophotography with your A7R/S? (I suppose your telescope has a 2" barrel)

 

Thank you for all the information you've been providing!  :applause:

 

Regards,

 

Claudius 



#460 bwallan

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Posted 03 October 2014 - 02:25 PM

Hello Brian,

 

Which adapter are you using for prime focus astrophotography with your A7R/S? (I suppose your telescope has a 2" barrel)

 

Thank you for all the information you've been providing!  :applause:

 

Regards,

 

Claudius 

See http://cncsupplyinc.com/ for adapters.  I'm sure there are similar chinese products available now but at the time I was looking CNC Supply was the only one I could find.

 

bwa



#461 claudius

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Posted 03 October 2014 - 03:00 PM

The information on the website is that their UltraWide 2" E-mount adapter (to 2" barrels) doesn't fit full frame models such as A7/R/S. So I thought you might have got yours somewhere else.



#462 bwallan

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Posted 03 October 2014 - 08:31 PM

The information on the website is that their UltraWide 2" E-mount adapter (to 2" barrels) doesn't fit full frame models such as A7/R/S. So I thought you might have got yours somewhere else.

There is no difference between an E mount and a FE mount as far as attaching to a NEX or A7 series camera.  The reason they may state this is the adapter does cause some vignetting when used with a full frame camera but I haven't found another adapter that is any better.  It all depends on the scope (and its light cone) being used with an A7+ camera.

 

The adapters are good quality and fit snugly on an A7S and A7R.  I purchased the T-Minus adapter as well as a couple of T-Ring for Sony NEX (E mount to T2 thread) adapters.

 

bwa



#463 RandyC

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Posted 03 October 2014 - 08:59 PM

Good EAA evening resolution seekers. Are you ready for a mouthful?

 

The DSLR to telescope adapter is one of the most complex setups I've ever seen. This will work for a Celestron SCT:

 

Plus: http://www.amazon.co...1?ie=UTF8&psc=1

Plus: http://www.bhphotovi...nt_adapter.html

 

Now here's the hard part, getting a 2" filter inside: http://www.sciencece...parts/index.htm

1. http://www.sciencece...s/html/7528.htm

2. http://www.sciencece...s/html/7522.htm

3. M57007(7mm extension tube) (ask Ted Ishikawa <ishikawa@hutech.com>;)

4. 7522 (w/52mm to 48mm stepping ring) (ask Ted)

 

This will fit a 2" filter inside the Borg assembly.

 

Ted at Hutech also sells a similar 2" filter assembly with SCT M-F threads, Ted Ishikawa <ishikawa@hutech.com>;

 

Celestron rear cells have a 1.5" inner diameter which is exactly the same as a T-ring. So there is no difference between using a SCT and T-ring thread set in aperture clearance.

 

My Mallincam fell out of the eyepiece holder too many times. Threads are better.

 

Whew, I need a drink of water now.

RandyC.

Attached Thumbnails

  • t-ring setup_Fotor.jpg


#464 claudius

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Posted 03 October 2014 - 09:20 PM


The information on the website is that their UltraWide 2" E-mount adapter (to 2" barrels) doesn't fit full frame models such as A7/R/S. So I thought you might have got yours somewhere else.

There is no difference between an E mount and a FE mount as far as attaching to a NEX or A7 series camera. The reason they may state this is the adapter does cause some vignetting when used with a full frame camera but I haven't found another adapter that is any better. It all depends on the scope (and its light cone) being used with an A7+ camera.

The adapters are good quality and fit snugly on an A7S and A7R. I purchased the T-Minus adapter as well as a couple of T-Ring for Sony NEX (E mount to T2 thread) adapters.

bwa

Understood, thanks!

Edited by claudius, 03 October 2014 - 09:24 PM.


#465 bwallan

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Posted 03 October 2014 - 09:44 PM

I normally add a 3rd party focuser to the back of an SCT or EdgeHD.  I find it much easier to get (and keep) a good focus:

C8-RedDot-Guide-WOFocuser-QHY8.jpg

Configuration: Scope, focuser, 2" nosepiece w/ T2 threads (or a reducer with 2" nosepiece and T2 threads), T2->mount adapter, camera of choice.

Standard 48mm filters screw into the end of the 2" nosepiece or you can add a filterwheel or a filter tray.

 

I have since swapped out the manual focuser for a MoonLite motorized focuser, per:

ADMParallelAdapterOnPierMountedEQ6ProWit

 

Many different approaches when using an SCT scope since it has a ridiculously large back focus.

 

Enjoy!

 

bwa


Edited by bwallan, 03 October 2014 - 09:45 PM.


#466 Relativist

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Posted 04 October 2014 - 01:36 PM

I'm curious, how much deeper can the A7s go than the human eye in video mode? How would we estimate/measure this, by magnitude?



#467 ccs_hello

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Posted 04 October 2014 - 02:09 PM

I'm curious, how much deeper can the A7s go than the human eye in video mode? How would we estimate/measure this, by magnitude?

Curtis,

 

See this description on human eye/human visual system

http://www.cambridge...s-human-eye.htm (in dark adapted situation, human eye ISO is about ISO 500 - 1000)

 

Naturally we know human eye has a built-in, non-removable lens, a limited integration time (upper bound is about 1/20 sec), lose color detection capability/SNR/Dynamic Range under very light,  but normally in day-light has a very high dynamic range and very high spatial resolution.

 

A7s movie mode (not called "video" per se) has the longest exposure time of 1/4 sec (not so great) but ISO as high as 409,600 (with not so great S/N and dynamic range.)

 

This should help getting the eye vs camera comparison under the proper context and could assist to figure out how many steps in between these two.

 

Clear Skies!

 

ccs_hello



#468 ccs_hello

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Posted 04 October 2014 - 02:24 PM

Can A7s owners confirm the following..

 

The HDMI connector of the A7s has no choice but to output "HD Video" at high frame rate, e.g., 30 frames/sec in 1080p @ 30FPS.

This is the limitation of the HDMI monitor and the actually video standards limitation.

This would be the case for 1/4sec exposure movie mode.  E.g., lot of frames show up in HDMI are redundant.

 

A7s during movie mode, its HDMI port is output "live" and can be the "clean" HDMI (i.e., no information text)  

 

If movie is recorded in 1/4 sec exposure time, only actual and individual exposed frames are compressed and recorded.  

I.e., no "artificially generated" redundant frames are ever encoded/compressed in the movie file.

 

Clear Skies!

 

ccs_hello



#469 ccs_hello

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Posted 04 October 2014 - 02:29 PM

Saw a very nice astro use of A7s writeup:

http://petapixel.com...ography-review/



#470 Relativist

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Posted 04 October 2014 - 03:14 PM

If I understand correctly, the A7s, outputs Ultra HD. So, combined with an ultra HD monitor, the A7s used in this way has the potential to give the eyepiece view a run for it's money.



#471 bwallan

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Posted 04 October 2014 - 05:39 PM

I'm curious, how much deeper can the A7s go than the human eye in video mode? How would we estimate/measure this, by magnitude?

Depends how high you push the ISO and how much noise you're willing to consider acceptable?

 

It also depends on how sensitive your night adapted eye is and this depends upon genetics, age, time for adaption, etc.

 

My best estimate from shooting a range of videos at 1/4sec exposure and various ISO's (using a 28mm, f/5.6 lens) is my night vision is about equivalent to video shot at ISO 51200.  At ISO's above 51200 the camera wins (if you can control or live with the noise).

 

bwa



#472 bwallan

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Posted 04 October 2014 - 05:52 PM

Can A7s owners confirm the following..

 

The HDMI connector of the A7s has no choice but to output "HD Video" at high frame rate, e.g., 30 frames/sec in 1080p @ 30FPS.

<<depends on the device receiving the signal.  The port will output 4K consumer video if the monitor/recorder will accept it>>

 

This is the limitation of the HDMI monitor and the actually video standards limitation.

<<yes>>

 

This would be the case for 1/4sec exposure movie mode.  E.g., lot of frames show up in HDMI are redundant.
<<yes>>

 

A7s during movie mode, its HDMI port is output "live" and can be the "clean" HDMI (i.e., no information text) 

<<yes, video is clean.  Video information is written to associated non-video files.>>

 

If movie is recorded with 1/4 sec exposure time, only actual and individual exposed frames are compressed and recorded.  

I.e., no "artificially generated" redundant frames are ever encoded/compressed in the movie file.

<<if recording at 30 fps and your exposure is 1/4sec (4 fps), the 1/4 sec frame will be output 7.5 times or 15 times if your recording rate is 60 fps.>>

 

Clear Skies!

 

ccs_hello

<<See inserted comments above>>

 

bwa


Edited by bwallan, 04 October 2014 - 11:09 PM.


#473 bwallan

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Posted 04 October 2014 - 06:08 PM

If I understand correctly, the A7s, outputs Ultra HD. So, combined with an ultra HD monitor, the A7s used in this way has the potential to give the eyepiece view a run for it's money.

The A7S will output everything up to 4K consumer grade video (3840x2160pixels) depending upon the device attached to the camera.

 

LiveView: 921,600 pixels.  Viewfinder: 2,359,296 pixels.  HD video (1920x1080): 2,073,600 pixels; about the same as the viewfinder.  4K video: 8,294,400 pixels; 3.5x the resolution of the viewfinder!!

 

bwa



#474 ccs_hello

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Posted 04 October 2014 - 07:26 PM

bwa,

 

AFAIK, A7s' rear LCD screen has the 640x480 resolution and its OLED viewfinder LCD has the 1024x768 resolution.  (I.e., 1 LCD display pixel = 3 dots = 1R + 1G + 1B dots.)

 

Clear Skies!

 

ccs_hello


Edited by ccs_hello, 04 October 2014 - 07:27 PM.


#475 ccs_hello

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Posted 04 October 2014 - 07:32 PM

RE:

If movie is recorded with 1/4 sec exposure time, only actual and individual exposed frames are compressed and recorded. 
I.e., no "artificially generated" redundant frames are ever encoded/compressed in the movie file.
<<if recording at 30 fps and your exposure is 1/4sec (4 fps), the 1/4 sec frame will be output 7.5 times or 15 times if your recording rate is 60 fps.>>

 

bwa,

 

Thanks for the info.  So I assume (using 60p 1/4 exp as an example), there will be 14 identical frames following one updated frame in AHCHD.  I would hope/assume the repeated 14 frames are all P frames. 

BTW, is there a fast time-lapse movie mode (using 1/4sec exp time) such that there will be no repeated redundant frames?

 

Clear Skies!

 

ccs_hello 




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