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Canon 700D vs ASI 224MC on 6" SCT - test three

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#1 Tulloch

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Posted 02 September 2019 - 06:42 PM

Hi again, still doing some comparisons between the Canon DSLR and the ASI224MC, but this test is a little different. Following on from a post put up by BQ, I wanted to compare the noise levels from both cameras and determine the minimum number of frames required to get a "good" result. This may interest some people, maybe not, but I'm posting it here for completeness.

 

I used the same data as I used for test one, as this seemed to give reasonable quality data for comparison purposes, and stacked a different number of frames for each camera. The results seem to indicate that the ASI224MC needs more frames to reduce the noise than the Canon 700D, which is fortunate since the Canon can only record 20 fps on my computer, while the 224 was recording at around 250 fps.

 

The results are below, the "sweet spot" for the ASI224MC seems to be about 8192 frames (with my processing), while the Canon 700D seems to be about 2048. Both sets of data were stacked in AS!3, sharpened and colour balanced in R6, levels changed in Photoshop to be 10/0.9/220, with saturation +15%. I didn't spend any time making the rind look better in these images.

 

Enjoy!

 

Andrew

Attached Thumbnails

  • Noise level study - frames stacked 700D ps1.jpg

Edited by Tulloch, 02 September 2019 - 08:01 PM.

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#2 Tulloch

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Posted 02 September 2019 - 06:43 PM

And the ASI224MC.

 

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  • Noise level study - frames stacked ASI224 ps1.jpg

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#3 petert913

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Posted 02 September 2019 - 07:30 PM

Those are some crazy-good results for a 6" scope !


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#4 descott12

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Posted 02 September 2019 - 07:49 PM

Great report but it is confusing.

The 224 is supposed to be the standard for planetary imaging. I thought because it was so low noise AND it could crank out hundreds of frames per second.

But your results indicate that a DSLR can beat it at 1/10 the frame rate and with a quarter of the frames.

So what am I missing? Did this only work because your seeing was crystal clear and you didn't need a fast frame rate? I am not familiar with that Canon Model but is it a really top of the line model?

 

Thanks again for a great post. And some really nice images.


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#5 Tulloch

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Posted 02 September 2019 - 08:08 PM

Those are some crazy-good results for a 6" scope !

Thanks Peter, the 6" SCT is performing well when the planets are nice and high in the sky for me in Oz right now smile.gif .

 

Great report but it is confusing.

The 224 is supposed to be the standard for planetary imaging. I thought because it was so low noise AND it could crank out hundreds of frames per second.

But your results indicate that a DSLR can beat it at 1/10 the frame rate and with a quarter of the frames.

So what am I missing? Did this only work because your seeing was crystal clear and you didn't need a fast frame rate? I am not familiar with that Canon Model but is it a really top of the line model?

 

Thanks again for a great post. And some really nice images.

Hi Dave, thanks for your observation.

 

While I don't think the Canon 700D (also known as Rebel T5i in the US and is only a middle of the road for Canon DSLRs) is producing better images than the ASI224MC, I think these tests are showing it can more than hold its own in reasonably good seeing on a small scope with a bit of practice. I'm yet to pit them against each other when the jetstream picks up (it was under 20m/s for the two times I've be out so far), where I suspect the differences between the two cameras will be more obvious.

 

Andrew


Edited by Tulloch, 03 September 2019 - 01:07 AM.


#6 RedLionNJ

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Posted 02 September 2019 - 09:28 PM

Hi Andrew,

 

Absolutely no surprises here from my perspective (as you may already know).

 

Given above-average seeing, I have never seen significantly better results from a CMOS planetary cam than from a DSLR.

 

I continue to watch your comparison results.....

 

 

Grant


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#7 Tom Glenn

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Posted 02 September 2019 - 10:10 PM

Andrew, I do enjoy the comparisons you are doing, despite the difficulties in performing any type of controlled experiment.  I've said many times in other threads that in many ways, the camera is the least important piece of equipment involved in the capture, provided that it is able to capture RAW data from the sensor.  World class results are obtained with a variety of cameras, including some models that are now 10 years old or even older.  Seeing conditions and technical skill of the imager (collimation and a slew of other factors) will always exceed the camera, provided raw data is captured.  In this respect, the Canon DSLRs are very good.  Many people that get started in planetary imaging with DSLRs don't appreciate the various modes that can be used for video, and with cameras that don't allow raw data to be recorded from a small portion of the sensor, the results will never equal what you are showing here.  


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#8 Tulloch

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Posted 03 September 2019 - 12:21 AM

Andrew, I do enjoy the comparisons you are doing, despite the difficulties in performing any type of controlled experiment.  I've said many times in other threads that in many ways, the camera is the least important piece of equipment involved in the capture, provided that it is able to capture RAW data from the sensor.  World class results are obtained with a variety of cameras, including some models that are now 10 years old or even older.  Seeing conditions and technical skill of the imager (collimation and a slew of other factors) will always exceed the camera, provided raw data is captured.  In this respect, the Canon DSLRs are very good.  Many people that get started in planetary imaging with DSLRs don't appreciate the various modes that can be used for video, and with cameras that don't allow raw data to be recorded from a small portion of the sensor, the results will never equal what you are showing here.  

Hi Tom, thanks for your comments here, I'm glad other people are finding this comparison work interesting as well as just me smile.gif.

 

It is certainly true that the camera is only one part of the whole imaging process, however I would like to point out that the Liveview stream from the Canon DSLR cameras is by no means the raw signal. It almost certainly has had some noise reduction applied along with colour balancing etc, and the output files are in jpg format. Granted, the amount of compression applied to the frames is almost zero (this link puts the jpg quality level at 99% compared to around 60% for the Nikon), however they are by no means a raw signal straight from the sensor. I think this internal noise reduction is why less frames are required for an acceptable final image to be produced at lower stacking numbers that the ASI224MC. Below are what AS!3 assessed as the "best" frames out of the stacks I used, first the Canon 700D, second the ASI224MC. You can certainly see the difference in noise level from the "raw" frames straight out of the different cameras..

 

It appears that Canon DSLRs are the only ones capable of this kind of high quality output stream needed for planetary imaging. The Nikon systems compress their Liveview stream too much, and I have't seen anyone else use other types of DSLR for this purpose. So while the camera might not be the most important part of the setup, choosing the wrong one will certainly limit the quality of the final result.

 

Andrew

Attached Thumbnails

  • Canon 700D best frame.png
  • ASI 224MC Best frame.png

Edited by Tulloch, 03 September 2019 - 12:22 AM.

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#9 BQ Octantis

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Posted 10 September 2019 - 01:02 AM

Wow!

 

So the advantage of the dedicated planetary camera is simply frame rate? I had already figured that you wouldn't defeat the physics of photonics—my capture settings on my T3i are 1/160sec at ISO12800 to get a minimum histogram, so 200 fps already seemed sporty—but I didn't realize the frame ratio between the two options was 4:1!

 

BQ



#10 Tulloch

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Posted 10 September 2019 - 02:06 AM

Wow!

 

So the advantage of the dedicated planetary camera is simply frame rate? I had already figured that you wouldn't defeat the physics of photonics—my capture settings on my T3i are 1/160sec at ISO12800 to get a minimum histogram, so 200 fps already seemed sporty—but I didn't realize the frame ratio between the two options was 4:1!

 

BQ

I think the difference in frame stacking to reduce noise is due to the inbuilt noise reduction in the DSLR that's performed before the live image is sent. Are you capturing the 5x Liveview video from the camera? If so, I'm pretty sure the shutter speed is fixed at 1/30 sec and cannot be changed. Liveview is just simulating the effect of increasing/reducing ISO/shutter speed from some standard values. I don't believe you are actually capturing at 1/160 sec, the camera is simulating the effect by simply adjusting the sensor gain to mimic the effect of a faster shutter speed by reducing the EV. 

 

One of my first posts on CN (which you replied to) concerned some tests I was doing by taking the liveview stream of an electric fan, when I changed the shutter speed (and increased ISO to keep the EV the same) it made absolutely no difference to the final image, the noise level, motion blur and everything else were identical. 

https://www.cloudyni...when-recording/

 

Unless you are actually recording video with a shutter speed of 1/160 sec and ISO 12800, well that's completely different.

 

Andrew


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#11 BQ Octantis

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Posted 10 September 2019 - 02:39 AM

I think the difference in frame stacking to reduce noise is due to the inbuilt noise reduction in the DSLR that's performed before the live image is sent. Are you capturing the 5x Liveview video from the camera? If so, I'm pretty sure the shutter speed is fixed at 1/30 sec and cannot be changed. Liveview is just simulating the effect of increasing/reducing ISO/shutter speed from some standard values. I don't believe you are actually capturing at 1/160 sec, the camera is simulating the effect by simply adjusting the sensor gain to mimic the effect of a faster shutter speed by reducing the EV. 

 

One of my first posts on CN (which you replied to) concerned some tests I was doing by taking the liveview stream of an electric fan, when I changed the shutter speed (and increased ISO to keep the EV the same) it made absolutely no difference to the final image, the noise level, motion blur and everything else were identical. 

https://www.cloudyni...when-recording/

 

Unless you are actually recording video with a shutter speed of 1/160 sec and ISO 12800, well that's completely different.

Yep, I'm capturing at 5x zoom to get the ~1:1 pixel ratio. I realize the 1/160sec is simulated in LiveView (Jerry Lodriguss clued me into this last year, and some noise tests with the lens cap on showed no difference in the noise pattern across ISOs for the same EV), but it's still a valid reference point for the total EV for a given f-number (12800×1/160 = 80). So if the Canon EOS exposure is fixed at 1/30sec, then my camera's using an ISO of 80 ÷ 1/30 = 2400. By comparison, to get 1/200sec the dedicated cam would have to be using an ISO higher than 12800.

 

Where did you find the 1/30 reference? I hunted high and low last year and never came across it, but I searched specifically on the 600D/T3i…

 

BQ

 

P.S. If the exposure difference is 1/30 vs. 1/200, then this would mean that a planetary camera needs 1/30 ÷ 1/200 = 6.7 frames to equate to one EOS frame; so the ratio would be 6.7:1. Does that mean the planetary cam can handle turbulence 6.7 times worse than a DSLR?


Edited by BQ Octantis, 10 September 2019 - 02:59 AM.


#12 Tulloch

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Posted 10 September 2019 - 04:36 AM

Yep, I'm capturing at 5x zoom to get the ~1:1 pixel ratio. I realize the 1/160sec is simulated in LiveView (Jerry Lodriguss clued me into this last year, and some noise tests with the lens cap on showed no difference in the noise pattern across ISOs for the same EV), but it's still a valid reference point for the total EV for a given f-number (12800×1/160 = 80). So if the Canon EOS exposure is fixed at 1/30sec, then my camera's using an ISO of 80 ÷ 1/30 = 2400. By comparison, to get 1/200sec the dedicated cam would have to be using an ISO higher than 12800.

 

Where did you find the 1/30 reference? I hunted high and low last year and never came across it, but I searched specifically on the 600D/T3i…

 

BQ

 

P.S. If the exposure difference is 1/30 vs. 1/200, then this would mean that a planetary camera needs 1/30 ÷ 1/200 = 6.7 frames to equate to one EOS frame; so the ratio would be 6.7:1. Does that mean the planetary cam can handle turbulence 6.7 times worse than a DSLR?

OK, I'm guessing at the 30 fps framerate for Liveview based on the stats that I've been been able to find online for similar cameras (although having said that, the 700D appears to be updating at 60 fps, I never found this before! It must be a mistake, every other camera is 30 fps.).

 

80D - https://www.canon.ie...ml#liveviewmode

800D - https://www.canon.ie...specifications/

600D - https://www.canon.ie...ml#liveviewmode

700D - https://www.canon.ie...ml#liveviewmode

550D - https://www.canon.ie...ml#liveviewmode

60Da - https://www.canon.ie...ml#liveviewmode

 

When I brought up the issue of atmospheric turbulence and "freezing the seeing", Tom Glenn gave some additional insights into the nature of atmospheric distortion. I believe that some of the total distortion comes from high frequency "motion shifts" where the planet just moves as a complete disc and a fast frame rate might help, but other distortion that comes from path length differences through the atmosphere that causes the planet to distort or change shape away from circular that a fast frame rate can't fix. 

https://www.cloudyni...ng-an-epiphany/

 

When Darryl recently took images of Jupiter in high winds and still was able to create his usual extremely high standard of images using a 224, that was a turning point for me. There is no way that my DSLR could take images in that situation, indeed, when I was capturing under a low windspeed moving the scope slightly, I couldn't get any decent images out of that session.

https://www.cloudyni...-grs-close-ups/

 

It is well known that the Quantum Efficiency of the ASI224MC is higher than the DSLR (75-80% vs 40%), and being able to stream over USB3 is certainly an advantage.

https://astronomy-im...roduct/asi224mc

https://www.ideiki.com/astro/EOS.aspx

 

So I ultimately purchased the ASI224MC because I thought the DSLR was hindering my progression in this field, by restricting me to only be able to take good images in very good to perfect conditions. I still believe the Canon DSLR system is able to match the dedicated planetary cameras in good+ conditions and am keen to continue to do some these tests to show the limitations of each, but in the future I think the 224MC will give me better outcomes.

 

Andrew


Edited by Tulloch, 10 September 2019 - 05:57 AM.


#13 BQ Octantis

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Posted 12 September 2019 - 05:04 AM

OK, I'm guessing at the 30 fps framerate for Liveview based on the stats that I've been been able to find online for similar cameras (although having said that, the 700D appears to be updating at 60 fps, I never found this before! It must be a mistake, every other camera is 30 fps.).

 

80D - https://www.canon.ie...ml#liveviewmode

800D - https://www.canon.ie...specifications/

600D - https://www.canon.ie...ml#liveviewmode

700D - https://www.canon.ie...ml#liveviewmode

550D - https://www.canon.ie...ml#liveviewmode

60Da - https://www.canon.ie...ml#liveviewmode

 

When I brought up the issue of atmospheric turbulence and "freezing the seeing", Tom Glenn gave some additional insights into the nature of atmospheric distortion. I believe that some of the total distortion comes from high frequency "motion shifts" where the planet just moves as a complete disc and a fast frame rate might help, but other distortion that comes from path length differences through the atmosphere that causes the planet to distort or change shape away from circular that a fast frame rate can't fix. 

https://www.cloudyni...ng-an-epiphany/

 

When Darryl recently took images of Jupiter in high winds and still was able to create his usual extremely high standard of images using a 224, that was a turning point for me. There is no way that my DSLR could take images in that situation, indeed, when I was capturing under a low windspeed moving the scope slightly, I couldn't get any decent images out of that session.

https://www.cloudyni...-grs-close-ups/

 

It is well known that the Quantum Efficiency of the ASI224MC is higher than the DSLR (75-80% vs 40%), and being able to stream over USB3 is certainly an advantage.

https://astronomy-im...roduct/asi224mc

https://www.ideiki.com/astro/EOS.aspx

 

So I ultimately purchased the ASI224MC because I thought the DSLR was hindering my progression in this field, by restricting me to only be able to take good images in very good to perfect conditions. I still believe the Canon DSLR system is able to match the dedicated planetary cameras in good+ conditions and am keen to continue to do some these tests to show the limitations of each, but in the future I think the 224MC will give me better outcomes.

 

Andrew

I checked to see which ISO got me closest to my capture EV (1/160@ISO12800) at 1/30sec, and it was ISO3200. Here's a comparison of a video frame (on the left) and a JPEG still (on the right):

 

comparison.jpg

 

Upon close inspection, there's a bit more compression noise (particularly in the color) on the freeze frame, but they compare well…so the 1/30sec hypothesis seems plausible.

 

As to atmospheric seeing, there are indeed two resultant components to the wavefront correction model: low-order tilt and high-order distortion. In adaptive optics systems, professional astronomers use a fast steering mirror to remove tilt and a deformable primary mirror to remove the high-order distortions. For the amateur, a fast imaging cam only replaces the fast steering mirror; lucky imaging replaces the deformable. I've been holding out for an amateur deformable for over a decade, but there doesn't seem to be an appetite for one…yet…

 

BQ


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#14 BQ Octantis

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Posted 12 September 2019 - 07:18 AM

One other note. I was out shooting Saturn tonight and I decided to do a blowout capture to see if I could get the moons to stand out a little more in the stacker. As if to remove all doubt, the shutter speed at ISO12800 above which there was no further gain change was 1/30sec.


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#15 Tulloch

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Posted 12 September 2019 - 08:24 AM

One other note. I was out shooting Saturn tonight and I decided to do a blowout capture to see if I could get the moons to stand out a little more in the stacker. As if to remove all doubt, the shutter speed at ISO12800 above which there was no further gain change was 1/30sec.

Nice - I never actually did the test, I wasn't sure if it would tell me anything, but your test seems to have confirmed the theory (or at least hasn't disproved it - yet smile.gif).

 

After I made the assumption that shutter speed was fixed at 1/30 sec and aperture was fixed at f10 (or f26 with the 2x Barlow), then I assumed that changing either ISO or "shutter speed" in Exposure compensation mode in Live view simply changed the gain that was applied to the sensor. Therefore I didn't worry about what the actual numbers were, I just found some values that gave good histograms and usually tried to keep them. For Jupiter it usually worked out at ISO400 and 1/20 - 1/40 sec, Saturn was ISO800 and 1/10 - 1/20 sec.

 

Andrew


Edited by Tulloch, 12 September 2019 - 08:44 AM.


#16 BQ Octantis

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Posted 12 September 2019 - 04:17 PM

Nice - I never actually did the test, I wasn't sure if it would tell me anything, but your test seems to have confirmed the theory (or at least hasn't disproved it - yet smile.gif).

 

After I made the assumption that shutter speed was fixed at 1/30 sec and aperture was fixed at f10 (or f26 with the 2x Barlow), then I assumed that changing either ISO or "shutter speed" in Exposure compensation mode in Live view simply changed the gain that was applied to the sensor. Therefore I didn't worry about what the actual numbers were, I just found some values that gave good histograms and usually tried to keep them. For Jupiter it usually worked out at ISO400 and 1/20 - 1/40 sec, Saturn was ISO800 and 1/10 - 1/20 sec.

 

Andrew

Makes sense to me. I got beat up by Jerry when I referred to ISO as "gain", but that's essentially what the camera is doing—indeed, Bracken's Deep Sky Imaging Primer explains the two (gain and ISO) as a multiplier of the photon count. Moreover, the T3i will pick fractional ISOs between the ones I can select. So while the 1/30sec seems likely, but if I try to use a fixed 1/30sec exposure, I'm limited to 8 values, whereas I can access the in-between values by using ISO12800 and changing simulated shutter speed. As per my post before, I'm finding ISO2400 to be my go-to, but I access it with the setting 1/160sec@ISO12800.

 

BQ


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