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Samsung SCB-4000/2000 vs Canon T2i sensitivity

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#1 Moromete

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Posted 30 December 2012 - 03:51 PM

Will Samsung SCB-4000 or 2000 show more details on less bright DSOs (i.e. galaxies) than a Dslr like Canon T2i at ISO 1600 after a 4s or 10 seconds exposure?

Currently I'm using a Canon T2i with MagicLantern and C11 at F6 for video astronomy which enables 4s exposures in Liveview, similar to a Mallincam. It's ok for bright DSOs but not enough for live viewing of galaxies.
I should tell you that the T2i is getting quite hot during video astronomy.
I don't afford a Mallincam but I would like to know if the SCB-4000/2000 is considerably better/sensitive than a T2i for video astronomy.

Has anyone compared those CCTVs with a DSLR?


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#2 StarmanDan

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Posted 30 December 2012 - 06:11 PM

The CCTV will be more sensitive. I've seen the companion galaxies to the Deer Lick with my Sammy 2K & 8" SCT at f/6.3 and 512x exposure.

#3 ccs_hello

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Posted 30 December 2012 - 11:07 PM

I am unaware of that T2i can do "video", 4 second exposure, and "liveview" at the same time.

Can you elaborate?

BTW, DLSRs are designed mainly focused on high S/N while many of the devices mentioned in this specific subforum trading off that for "faster image acquisition time".

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#4 Moromete

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Posted 31 December 2012 - 03:26 AM

@ccs_hello: Yes, I do video astronomy with my Canon T2i + MagicLantern with frame integration time up to 4 seconds. For this in MagicLantern you need to set up the function FPSOverride to 0.15 and you'll obtain a Mallincam like image in 4s in LiveView. You'll see the image "growing" on the LiveView display.

As a side note, after a test on M42 I obtained the same image quality after a 4s photo with T2i or 4s in FPSOverride in LiveView on T2i. The difference was I could film M42, not picture it, with FPSOverride.

Problem is I don't know which device is more light sensitive after 4s, the T2i (with a bigger sensor) or Mallincam!

Keeping the idea, will the Mallincam show more on a galaxy after 50s integration time than 50s picture done with T2i, considering both devices accumulate photons during the same period of time?

Is the final result the same but only the method different?

Have you made such a comparison?

#5 Moromete

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Posted 31 December 2012 - 03:34 AM

@StarmanDan: How much more sensitive is the Samsung vs dslr in your experience? Can you exemplify to help me better understand the difference?

What dslr have you used for comparison?

Considering the Sammy 2k is limited to 10s integration time, will a DSLR show much more after, let's say, a 60s exposure?

#6 mclewis1

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Posted 31 December 2012 - 10:08 AM

The CMOS sensor in the DSLRs is not quite as senstive as the larger pixel/cell Sony CCD sensor used in the video cameras. But if you are comparing a camera's overall sensitivity you also need to look at the gain and noise reduction capabilities.

A commercial security video camera has similar gain characteristics to most DSLRs (which have come a long way in the past few years). A Mallincam is built to go beyond this by adding high quality amplifiers and internal cooling to further reduce noise and allow longer exposures.

Controlling internal heat is a big deal for continuously read sensors (during "live" viewing).

Security cameras tend to give you the best bang for your buck and lowest entry price points. Cameras with larger CMOS sensors (DSLRs/mirrorless) offer more resolution and larger fovs (and general photography capabilities) at the expense of some sensitivity (at both short and longer exposures). Purpose built video cameras (Stellacam/Mallincam) offer increased sensitivity over either of these other cameras.

It's very difficult to compare overall sensitivity of various cameras from just the manufacturers specifications (they all seem to use different testing methodologies and rarely at the extremely low light/contrast levels required for astronomy use). Because of this and huge number of variables (scope size and condition, f ratios, sky conditions, etc.) the only really effective method of comparison is side by side viewing and given the cost of the higher end cameras this isn't very popular.

#7 mattflastro

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Posted 31 December 2012 - 10:34 PM

How much more sensitive is the Samsung vs dslr ...? Can you exemplify to help me better understand the difference?

Considering the Sammy 2k is limited to 10s integration time, will a DSLR show much more after, let's say, a 60s exposure?


I don't think anybody actually measured the Samsung and various DSLR's sensitivity using a common test method, because a standard sensitivity test does not exist . Comparing measurements based on different tests carried on under different conditions would be misleading .

There are some examples of Mallincam (I know you asked about Samsung) images here:
http://mallincamproject.astrocpo.com/
However, the images are taken by different people with different gear so it's hard to make any direct comparison .

There are several aspects that will dictate the outcome of a DSLR vs. video cam comparison , and "sensitivity" is not the first of them .
The 2 most important issues are pixel size and CCD chip (diagonal) size .
Pixel size , winner is the video cam. A 1/2" or 1/3" CCD has a pixel area ranging from 32 um2 to 72 um2 (square microns ). A T2i has 18 um2 pixels . Assuming the same number of photons per unit of sensor area, the video cam receives 2 to 4 times more photons per pixel due just to this pixel size difference.
QE , Bayer filters , readout noise differences are very minimal .
Chip size matters and the winner here is NOT the larger size.
A 1/2" CCD has an 8mm diagonal, a 1/3" CCD has a 6mm diagonal. Canon T2i has a 26.6mm diagonal.
Let's assume you want to use the same scope and obtain the same field of view in order to frame the same subjects the same way in the video cam and the DSLR . The 1/2" CCD allows a focal ratio reduction 3.3 times more than the DSLR.
The 1/3" video cam allows a reduction of 4.4 times more than the DSLR.
Therefore , for the same scope and the same subject framing , the video cam receives 10 to 18 times more light per square micron of sensor area (goes up with the square of F reduction) .
Combine this 10 to 18 fold gain with the 2 to 4 times gain due to the larger pixel in the video cam and the result is the video cam pixels receive 20 to 32 times more light than the DSLR , for the same scope , same target and same image framing . Assuming similar QE , the video cam will capture an image on its sensor 20 to 32 times quicker than the DSLR . 17 sec max x 20 to 32 means 340 sec to 570 sec . What you see with the video cam in 17 seconds you will capture with the DSLR in 5 to 10 min .
This brings up another issue, which is the mount , with its tracking and polar alignment . You can get by with an alt/az setup and a quick and dirty polar alignment for 17 sec max exposure time but you need a good equatorial mount, good polar alignment (more time consuming) for 5 to 10 min . Then you also need to process the DSLR images , which adds even more time before you get to see the DSLR image .

Happy New Year

#8 mclewis1

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Posted 01 January 2013 - 03:54 PM

Oh I forgot to mention ... the Sony sensor in the Mallincam uses a CYMK vs RGB mask. The CYMK setup is also more sensitive.

#9 nytecam

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Posted 02 January 2013 - 04:52 AM

I've the original Canon 300d DSLR and recently the entry level 1100d which much superior to the 300d in image quality and sensitivity but its still no match for the Sony HAD Exview CYMK sensor used in many CCTV/ astro-cams like Mallincam and SX Lodestar-C etc. All sensors are highly sensitive to near-IR radiation [galaxies radiate in IR too!] but in DSLRs this is blocked to preserve good colour.
But what is good colour in inordinately faint DSOs that doesn't register on the eye? :o

Oh I forgot to mention ... the Sony sensor in the Mallincam uses a CYMK vs RGB mask. The CYMK setup is also more sensitive.

I've carried out comparative astro tests on my mono Lodestar and Lodestar-C one-shot-colour [OSC] cam that use Exview sensors and I rate the Lodestar-C @ ~60% the sensitivity of the Lodestar mono black&white cam so 60s mono needs a modest increase to 100s for similar image density but seen in glorious, if imperfect, colour :grin:

I've used both Lodestars on my astro-spectrograph and greater than one third of the radiation recorded is in near-IR which, with pale CYMK on-chip filters, greatly boosts the cam's sensitivity ;) DSLR - no chance :p

Three recent DSO pics taken under a bright moonlight in Cigar Gxy, Bodes Gxy and Iris Neb :lol:



#10 ccs_hello

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Posted 02 January 2013 - 11:08 PM

Videocams are still using complementary-color (CMY) then add G Bayer matrix while webcams and DSLRs, etc. now mostly use RGB (primary-color) Bayer array filter to get better color fidelity (which is mostly meaningless in astrophotography.)

The former has clear advantage over broadband spectrum emission objects. I.e., higher energy intake equals higher Signal output.

S/N stuff has a long story and many attributes to deal with. It's part of image science...

P.S. CMYK (K = black) is used in printing world for obstruct light reflection (absorb light). It's the opposite of let the light to shine in/pass through as in image sensors. :) :)

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#11 Moromete

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Posted 03 January 2013 - 07:33 AM

If I understood well, after a similar 4 seconds exposure a cctv like Samsung SCB2000/4000 will capture much more light than a DSLR like Canon T2i.

Under these circumstances the next logical question is: in 8 seconds (or 512x) will the Samsung still capture much more light than the T2i exposed for 1-1.5 minutes?

If the final result is quite similar, than for me a Samsung CCTV investment is not worth it.

I use the dslr just to see more than in the eyepiece but NOT to take processed pictures. I don't have time or mood for stacking frames on PC or taking dark frames.

My CG5-GT unguided mount gives me quite round stars at maximum exposures of 1-1.5 minutes with a very good polar alignment.

Last night I discovered after 1 year that I can take my C11 down to F3.5 from F6 with the AlanGee telecompressor. :D

#12 mpgxsvcd

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Posted 03 January 2013 - 04:16 PM

If I understood well, after a similar 4 seconds exposure a cctv like Samsung SCB2000/4000 will capture much more light than a DSLR like Canon T2i.

Under these circumstances the next logical question is: in 8 seconds (or 512x) will the Samsung still capture much more light than the T2i exposed for 1-1.5 minutes?

If the final result is quite similar, than for me a Samsung CCTV investment is not worth it.

I use the dslr just to see more than in the eyepiece but NOT to take processed pictures. I don't have time or mood for stacking frames on PC or taking dark frames.

My CG5-GT unguided mount gives me quite round stars at maximum exposures of 1-1.5 minutes with a very good polar alignment.

Last night I discovered after 1 year that I can take my C11 down to F3.5 from F6 with the AlanGee telecompressor. :D


Both sensors see the exact same light if the telescopes and focal reducers are the same. The real question is how much gain does each camera apply.

For the Samsung it might express the gain as 512x or a specific LUX number. The interchangeable Lens Camera will express it as a shutter speed and ISO exposure value.

If you can figure out how those numbers are equated then you can figure out which one needs more exposure time to make an equivalent picture.

In the cases I have seen it takes about ISO 12,800 for an interchangeable lens to equate to the good "video cameras". The T2i will not look good at ISO 12,800. The newest cameras will though.

You also have to look at the filter that is or is not used on the cameras and how much dynamic range each camera has.

The dynamic range on a large sensor camera is going to be vastly superior to that of the smaller sensor cameras. In the neighborhood of 2-8 stops.

However, the stock filter on most DSLR cameras will all but eliminate the Ha, UV, and IR light. That may or may not be taken out with the video camera.

If you are trying to image in UV, Ha, or IR spectrum then the video camera could possibly have 4-10 stops advantage. That would be huge. However, most of the interchangeable lens cameras can have their stock filter removed/replaced for a few hundred dollars.

#13 Moromete

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Posted 04 January 2013 - 02:38 AM

I see your point.

I was thinking of a max exposure of 512x (8s) for Samsung and one 1-1.5 minutes (no more because I don't autoguide, just use Celestron ASPA) exposure for Canon T2i at max ISO1600.

In my humble experience theres is no point to use a higher ISO with T2i because image is degrading at long exposures. I feel ISO800 is optimum for T2i for imaging DSOs.

#14 mclewis1

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Posted 04 January 2013 - 01:15 PM

Both sensors see the exact same light if the telescopes and focal reducers are the same. The real question is how much gain does each camera apply.

While it's true that the same amount of light is falling on the surface of the sensor it is not the case that each sensor offers the same sensitivity so it's much more than just the gain the camera provides. Starting with a more sensitive sensor gets the camera's electronics more data or signal to work with. From that point the better gain and lower noise takes over to provide a better image of low light low contrast details. When someone is evaluating a camera for deep sky observing/imaging it's the sum of all the components (sensor, read amps, interface, cooling, packaging, power consumption, etc. etc.) that determines the more appropriate product.

The dynamic range on a large sensor camera is going to be vastly superior to that of the smaller sensor cameras. In the neighborhood of 2-8 stops.

Travis, What cameras are you referencing? In general dynamic range doesn't have anything to do with the size of the sensor. It is simply the ratio between the signal and the noise. If you are starting out with more signal in each cell or pixel and are using similar low noise high gain electronics then you will have more dynamic range.

However, the stock filter on most DSLR cameras will all but eliminate the Ha, UV, and IR light. That may or may not be taken out with the video camera. If you are trying to image in UV, Ha, or IR spectrum then the video camera could possibly have 4-10 stops advantage. That would be huge. However, most of the interchangeable lens cameras can have their stock filter removed/replaced for a few hundred dollars.

I agree, the filter situation does indeed make a big difference (Ha in particular is very important when viewing most extended nebula and galaxies). Security cameras usually come with a generally poor quality filter in place. Removing that filter can dramatically increase the amount of signal in those specific parts of the spectrum. Some security cameras offer an automated capability to slide the filter out of the way of the sensor, on others you have to physically remove the sensor completely. On the purpose built astronomy oriented cameras there usually is no filter at all. You then add back high quality, higher transmission and sometimes narrow band filters designed specifically for astronomy imaging.

#15 nytecam

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Posted 04 January 2013 - 02:39 PM

P.S. CMYK (K = black) is used in printing world for obstruct light reflection (absorb light). It's the opposite of let the light to shine in/pass through as in image sensors. :) :)Clear Skies!ccs_hello

Yep - I fell for that quote without checking - should read CYMG pixel matrix :grin:

#16 mpgxsvcd

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Posted 07 January 2013 - 01:24 PM

The dynamic range on a large sensor camera is going to be vastly superior to that of the smaller sensor cameras. In the neighborhood of 2-8 stops.

Travis, What cameras are you referencing? In general dynamic range doesn't have anything to do with the size of the sensor. It is simply the ratio between the signal and the noise. If you are starting out with more signal in each cell or pixel and are using similar low noise high gain electronics then you will have more dynamic range.


Yes there is not a direct correlation to size of sensor and dynamic range. However, full frame sensor's almost always have more dynamic range than smaller sensors. There are a lot of factors in that though.

There are also many different definitions for dynamic range. I was using this definition from wiki.

"Dynamic range is the ratio between the largest and smallest possible values of a changeable quantity, such as in signals like sound and light. It is measured as a ratio, or as a base-10 (decibel) or base-2 (doublings, bits or stops) logarithmic value."

The common definition is that dynamic range is the ratio or number of stops from clipped white to clipped black.

14 bit RAW vs. 8 bit jpg(or equivalent), sensor technology...etc. Those all affect dynamic range. The Nikon D800 measured 14.4 EV with DXO mark. I know that their results are suspect but there are plenty of other tests that show cameras of that level achieve 13-14 stops.

The output format also affects dynamic range greatly. For instance there is a huge difference between 8 bit JPG and 14 bit RAW. So it really depends on how you are viewing the image. That is why I listed a broad range.

There is also the fact that some interchangeable lens cameras can do HDR images in camera and some can also do single exposure high dynamic range images. Those can simulate 1 to 2 extra stops.

Really there are so many different definitions and ways to test dynamic range that you can't accurately compare them. However, take equivalent images of Orion's nebula and let's see which camera blows out the core first. That should give you the results I stated.

#17 mpgxsvcd

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Posted 07 January 2013 - 01:35 PM

Both sensors see the exact same light if the telescopes and focal reducers are the same. The real question is how much gain does each camera apply.

While it's true that the same amount of light is falling on the surface of the sensor it is not the case that each sensor offers the same sensitivity so it's much more than just the gain the camera provides. Starting with a more sensitive sensor gets the camera's electronics more data or signal to work with. From that point the better gain and lower noise takes over to provide a better image of low light low contrast details. When someone is evaluating a camera for deep sky observing/imaging it's the sum of all the components (sensor, read amps, interface, cooling, packaging, power consumption, etc. etc.) that determines the more appropriate product.


The problem with this theory is that it just assumes that one camera is more sensitive than the other. You just state that one camera is more sensitive than the other.

Given the same exposure settings(Aperture, Shutter Speed, and sensitivity gain) the images will only differ in resolution, noise, and dynamic range. Their exposures will be the same.

The issue is that we don't know what sensitivity gain(ie: 512x) on the specialized cameras equates to the same sensitivity gain(ISO) on the interchangeable lens cameras. We can only guess without a 1:1 comparison.

I propose that we do that test. I for one would love to see a specialized camera and a newer interchangeable lens camera compared with the exact same setup. I don't want to do it to say this camera is better than another. They all have their strengths and weaknesses.

I just want to figure out what the strengths and weaknesses are of each camera so we know better how to utilize them. For instance something with greater dynamic range will probably give you a better image of M42 while something with high Ha sensitivity will give you a better image of the Horse Head.

I just would like to see some concrete samples they show the differences instead of vague generalizations that one camera is "More Sensitive" than another so it must be better for everything.

I am willing to run the test I just need some other cameras to test it with. I would even drive a distance with my equipment to meet someone if you live in the North Carolina Region.

#18 mclewis1

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Posted 07 January 2013 - 02:48 PM

Travis,

I'm with ya 100% on both posts.

The "more sensitive" comment is about the sensor, not the camera. The "more sensitivity sensor" is the Sony ICX 428AKL (ExView HAD) chip. With a sensitivity of 1600mv (from those big 8.4 x 9.8 um cells and CYMK filters) any camera that starts off with that chip is going to have a leg up on just about anything else out there ... and then of course there's the pre amp/amp gain, A/D conversion (and bit depth), noise reduction, etc. etc.

#19 Moromete

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Posted 08 January 2013 - 11:23 AM

The image of M31 below is taken by me with a C11 at F3.5 with AlanGee telecompressor on a CG5-GT and Canon 550D. This is not processed or stacked at all and unguided too, at ISO 3200 and a single 120s exposure. The 550D was set with High Iso Reduction on AUTO.

Can a LNTECH-300 show me much more on M31 after an exposure of 17/20s (1024x) with the same telescope?

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#20 mattflastro

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Posted 08 January 2013 - 11:38 AM

you can't get M31 to fit on a Samsung or Lntech sensor with the same telescope and same reducer. You need to reduce the focal length another 4 times to match the same field of view as in your 550D image.

#21 mpgxsvcd

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Posted 08 January 2013 - 11:56 AM

you can't get M31 to fit on a Samsung or Lntech sensor with the same telescope and same reducer. You need to reduce the focal length another 4 times to match the same field of view as in your 550D image.


An 11" F.875 telescope would be really cool. :shocked:

#22 Moromete

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Posted 08 January 2013 - 12:18 PM

Ok,but I wasn't referring to the field of view. I was referring to the amount of detail (like arms, color, etc) captured on M31. My mistake I wasn't clear enough.

I realize that FOV with a CCTV will be smaller even if I didn't know how much smaller.

#23 mpgxsvcd

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Posted 08 January 2013 - 12:24 PM

Ok,but I wasn't referring to the field of view. I was referring to the amount of detail (like arms, color, etc) captured on M31. My mistake I wasn't clear enough.

I realize that FOV with a CCTV will be smaller even if I didn't know how much smaller.


The field of view between the CCTV camera and APS-C is so different that the objects would not be similar at all. The difference really is quite significant when dealing with large objects like M31.

The larger sensor will fit the object in the field of view. The smaller sensor simply won't.

#24 Moromete

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Posted 08 January 2013 - 12:51 PM

Dame, I haven't made myself clear again. :bawling:

In this case, to be more clear, let's replace M31 with a faint and small DSO and keep the same question.

#25 ccs_hello

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Posted 08 January 2013 - 07:18 PM

All image devices have multiple attributes to compare with. To make a fair comparison, some test conditions must be normalized first and there is no clear winner on all fronts.

At the end of day, it's all tradeoffs. Many situations seen in this subforum have been S/N vs. fast(er) image acquisition time debate.

Price, better S/N, or fast image acquisition time, can only pick two. <-- Did you notice I didn't even bother to use a quite "polluted" term: sensitivity?

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