CCD or Sony a7s?

[bwana]

Post #58 Ole (Xplode) flipped,  Interesting thread you've started here, thanks - interesting to follow.    

Stunning seeing the exposure time on these shots, Brian's (bwana) Sony A7S numbers are something, half hours work and he's done.

Yes, but did you see the detail in the mono Ha Heart nebula?  Wow!

bwa

[bwana]

I still think Molly (Mono and Olly)  is normal, and a7s is flipped. But I really want to try one out just to see it in action

They look pretty much the same orientation to me.  I do know that PixInsight rotates A7S RAW subs by 180 deg. in processing.  It accepts JPG subs as taken, i.e.: no change in orientation.

bwa

[bwana]

They are indeed good for the exposure times and do make me wonder about the future of chip technology.

Olly

I read an article not that long ago about the future of camera sensors.  Apparently sensor technology has advanced to the point where each photosite could be a miniature spectrograph, determining the wavelength of the light it receives directly and outputting a signal equivalent to color.  No filters required!!  In-camera processing would simply involve specifying the portion of the spectrum you wish to see in the image; Ha, Oiii, Sii, RGB, UV, IR, whatever by simply selecting upper and lower limits.  The spectrum capable of being imaged would only be limited by whether the sensor was sensitive to that portion of the spectrum.

The analogy is radio.  You would essential "tune" the camera to pick up the "stations" wanted.

Although, like most research, I'll believe it when I have the camera in my hands...

bwa

[bwana]

...

All I need is bwana to give me his a7s : O)

I might sell it to you at a discount when the next generation of A7S's hits the market...

bwa 

[Mick J]

Yes, but did you see the detail in the mono Ha Heart nebula?  Wow!

bwa

Think I may have noticed it   

also I have an idea about the work/optics/skys/skills.......... 

[vertigo262]

I might sell it to you at a discount when the next generation of A7S's hits the market...

bwa 

bwa,

You might be right about the radio analogy. But probably not at this point. But could be very soon for all we know. But then, I've never tried a good ccd, or mono, or a a7s, so what do I know.

No, your supposed to give it to me for free, cuz I'm special! lol

[laser_jock99]

Would be interesting to try an A7S on a widefield F2.9 Newtonian in a dark sky site. The full frame chip would be wasted though- my corrected imaging circle is only 20mm diameter, barely enough to cover an APS-C chip.

[doormij]

The Sony A7 s has more noise then the Canon 6 d or 5 dmk3, on  http://www.centralds.net/cam/?p=7911 they write:

"In our tests we found that the noise level is higher than that of 6D, 5D markIII but the low light, high iso performance of A7s is so special"

Here the link for the Canon 6 D: http://www.centralds.net/cam/?p=7828

The darkframe comparison images show this clearly, here a combined darkframe image of the two cameras:

What we all want is a real test under the stars, this means both cameras (a7 and the 6D) on two small telescopes (small lenses) on one mount, take several images:

short and long exposure, high and low iso, brite nebula and a dark area of the sky and make the raw available for anyone to process.

Garrett

[kalasinman]

The A7s responds pretty well to mod. I think it will take a chunk out of the other makers market share, particularly for packable uses.

[bwana]

The Sony A7 s has more noise then the Canon 6 d or 5 dmk3, on  http://www.centralds.net/cam/?p=7911 they write:

"In our tests we found that the noise level is higher than that of 6D, 5D markIII but the low light, high iso performance of A7s is so special"

Here the link for the Canon 6 D: http://www.centralds.net/cam/?p=7828

The darkframe comparison images show this clearly, here a combined darkframe image of the two cameras:

What we all want is a real test under the stars, this means both cameras (a7 and the 6D) on two small telescopes (small lenses) on one mount, take several images:

short and long exposure, high and low iso, brite nebula and a dark area of the sky and make the raw available for anyone to process.

Garrett

Back in Feb 2015 a friend and I shot 30 sec. darks off the Sony A7S, A7R & A7 II and the Canon 7D II, 6D, 60D & XTi.  We analyzed the noise of the darks in three different ways: 1) PixInsight's Noise Evaluation utility, 2) Photoshop, and 3) simply the JPG file size as KB/MPixel.  The results from the three approaches were somewhat the same in the temperature range 20-23C:

Compared to the Canon 6D at ISO 3200:

- the A7S: same noise at ISO ~8000

- the 6D: fits here at ISO 3200

- the A7R: same noise at ISO ~2400

- the A7 II: same noise at ISO ~2200

- the 7D II: same noise at ISO ~1400  (APS-C)

- the 60D: same noise at ISO ~800  (APS-C)

- the XTi: same noise at ISO ~640  (APS-C)

This compares nicely to what I've seen in images off the cameras.  The A7R is about 2-3 stops better than the 60D, and the A7S is about 2-3 stops better than the A7R.

But analyses are one thing, images are what count...

bwa

[dph1nm]

Compared to the Canon 6D at ISO 3200:

Don't you need to know the gain at the various ISO to make this comparison? What matters in the noise in e- not ADU.

NigelM

[bwana]

Don't you need to know the gain at the various ISO to make this comparison? What matters in the noise in e- not ADU.

NigelM

On a DSLR/mirrorless camera ISO is equivalent to the Gain (on a CCD).

The noise as reported out of PixInsight is the same (3.23E-04) for the ISO's shown.  Interestingly, Sigma Noise reported for the A7S and A7R was 0.0 at ISO 100 and 1.68E-04 for the 60D (the only three tested at ISO 100).

bwa

[dph1nm]

On a DSLR/mirrorless camera ISO is equivalent to the Gain (on a CCD).

It should be proportional to ISO for a particular model.  but it may/will differ between cameras. In fact if you look at

http://www.clarkvision.com/articles/digital.sensor.performance.summary/#unity_gain

you will see the unity gain varies quite strongly with pixel size on the sensor.

NigelM

[vertigo262]

This is interestin 

I went out tonight and took some ha on my canon 7D full spectrum. 

removed the red channel and stretched it

Noises is horrible, but here is one. doesn't much look like the pictures I usually see. I think the mono has less noise, and the resolution of course is higher without the bayer 

[bwana]

It should be proportional to ISO for a particular model.  but it may/will differ between cameras. In fact if you look at

http://www.clarkvision.com/articles/digital.sensor.performance.summary/#unity_gain

you will see the unity gain varies quite strongly with pixel size on the sensor.

NigelM

I think we're sorta talking two different things.  I know ISO is (almost) proportional to Gain on any particular camera.  But ISO and Gain are equivalent across DSLR, mirrorless and CCD platforms, i.e.: we talk ISO on DSLR's and Gain on CCD's...

bwa

[bwana]

This is interesting 

I went out tonight and took some ha on my canon 7D full spectrum. 

removed the red channel and stretched it

Noises is horrible, but here is one. doesn't much look like the pictures I usually see. I think the mono has less noise, and the resolution of course is higher without the bayer 

ha test3.jpg

Is this the original 7D or the new 7D II?  Is there much difference between the two versions?

What equipment were you using and exposures/ISO?

bwa

[Psychobilly]

Based on personal experience there is little or no comaprison between the old 7D and the new 7DII ..

I had my original 7D converted to Full Spectrum a few days ago and so far It's proving to be a noisy beggar... I have read elsewhere that the high speed multi channel  readout needed for High FPS shooting is one of the causes and something they tackled in the 7DII

I wanted it for IR pass Terrestrial as well and it is OK for that...

Peter...

[vertigo262]

it's the original

300 seconds, iso 800 

ED 127mm scope

advanced vx mount 

[sharkmelley]

It's impossible to simply compare dark frames from 2 different cameras (e.g. Canon EOS 6D and Sony A7S) and get meaningful results.  The data needs to be scaled to consistent units i.e. electrons and then calibration frames must be applied - since this is what will typically be done during processing.  Using calibrated frames also allows the dark current to calculated.

Here's an example from the A7S - a friend kindly took 30 dark frames in succession at an indoor ambient temperature of around 20C.  On a typical dark frame, the noise you are seeing is the hot and warm pixels.  Subtracting two frames allows this coherent noise to be removed and then the resulting (difference) noise can be analysed to calculate the dark current.

Mark

[bwana]

It's impossible to simply compare dark frames from 2 different cameras (e.g. Canon EOS 6D and Sony A7S) and get meaningful results.  The data needs to be scaled to consistent units i.e. electrons and then calibration frames must be applied - since this is what will typically be done during processing.  Using calibrated frames also allows the dark current to calculated.

Here's an example from the A7S - a friend kindly took 30 dark frames in succession at an indoor ambient temperature of around 20C.  On a typical dark frame, the noise you are seeing is the hot and warm pixels.  Subtracting two frames allows this coherent noise to be removed and then the resulting (difference) noise can be analysed to calculate the dark current.

SonyA7S_DarkFrames.jpg

Mark

I'm not comparing dark frames from different cameras.  I'm comparing PixInsight's noise evaluation results on the various dark frames.  I'm not only interested in dark current.  I'm very much interested in the total noise in an image.  I don't use darks, flats or bias subs in processing so this is very important to me.

I'm not saying dark current isn't important, it is.  It's just that total noise is more important to the way I process astro-images.

bwa