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Author Topic: CCD and CMOS  (Read 18066 times)
ondebanks
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« Reply #40 on: September 29, 2011, 05:42:26 PM »
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1. You clearly quoted that I was confusing LONG EXPOSURE with HIGH ISO performance, while you are talking to a 30 years "quite well" known photographer that is at least respected for his work at more than one countries as if his knowledge was the knowledge of an ignorant kid! Clearly to take a part of the whole statement to "analyze" like if the the answer wasn't in front of you on the rest of the statement, is because: a) you intented to do so ....or b) there was not much oxygen in the room and you missed it from "eye blaring"   Embarrassed

Here is the entire, unedited first post you made in this thread. I encourage others to read it:

Quote from: larkis on September 25, 2011, 08:46:11 AM
Could someone give me a technical explanation why CMOS can shoot at such high ISO's (nikon D700, etc) compared to CCD's despite CCD's being more sensitive to light and being a more expansive technology ? A friend of mine is a scientist and tells me that in astronomy and industrial applications the reverse of what is going on in the camera business is true, CCD's are more light sensitive and have less noise compared to CMOS. I noticed with most cameras that use CCD's (like the phase backs) anything over 800iso is not really considered to be great. The sensors that go to space are also CCD's.


All MFDBs are CCD (up to now), the P1 P25+ and P45+ are the world leaders in low light because of their ability to keep the sensor cool for long exposures, this is due to the great cooling system not the type of sensor used, the MFDBs are worst in their ISO performance because they lack any kind of noise reduction filter or circuit, this is a choice of the manufacturers due to the demand of the MF market for purity so that low ISO performance is maximum! The IQ of DBs is well beyond any modern DSLR even if they are 5 or 6 years old! The reason for CMOS sensors is mainly the low cost of production, but they do cost a lot more than CCDs to develop. I guess that the production volume of DSLRs compensates for the high development cost of CMOS. CCDs are considered sharper and with greater color than CMOS, I'm not aware which technology is better for high Iso, to compare that we should have a comparison of cameras with both technologies but the same NR system. Regards, Theodoros. www.fotometria.gr

So - in answer to the OP's question, which asked only about high ISO and never once mentioned long exposures, your first explanation connects "low light" with "long exposures". What else were we to think, but that you were confused between them? We can only read it the way you write it.

2. Your second INSULT, has been answered already  Shocked  Huh

I still have no idea what my insult was? If an apology is warranted, how can I apologise if I don't know what I'm apologising for?!


3. It has been answered already to another quoter and you PARTIALLY accepted it up there, ......I've no intention (although I can) to be drugged in such a conversation, There is NO DSLR that turns its NR OFF when its instructed by the user to do so and .....thats it!! If you have a proof for the opposite (PROOF NOT THEORY like ...if it was so... then.... so it should.... that article says....), then ....I can interfere for you to have a really good job in the industry, ......I will even help you in your photography if you want!  Roll Eyes Regards, Theodoros. www.fotometria.gr

Thanks, but I already have a really good job, as a university lecturer in physics and astronomy. I teach a course on signal processing, another on astronomical data analysis, and another on observational astronomy, with a particular emphasis on detector issues. I've been doing digital image processing since 1992; my PhD thesis concerned calibrating astronomical imaging photon-counting detectors called MAMAs, and their use in high-resolution imaging, photometry and deconvolution of the centres of star clusters.

But I guess a British MechEng BEng degree trumps that.

Now I AM annoyed, because you're the first person ever on LuLa to force me to play the "my credentials are better than yours" card, and I really hate doing that. The letters after one's name should have nothing to do with anything in a discussion like this. Only the ability to present proper evidence matters. We're still waiting for yours...
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PierreVandevenne
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« Reply #41 on: September 29, 2011, 06:29:11 PM »
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CCDs are considered sharper and with greater color than CMOS

CCD or CMOS's don't have "greater color". They don't have any color. They count photons. You can filter photons before they reach the CCD, by means of an individual filters or a filter matrix (for example Bayer).
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fotometria gr
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« Reply #42 on: September 29, 2011, 07:03:10 PM »
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Here is the entire, unedited first post you made in this thread. I encourage others to read it:

Quote from: larkis on September 25, 2011, 08:46:11 AM
Could someone give me a technical explanation why CMOS can shoot at such high ISO's (nikon D700, etc) compared to CCD's despite CCD's being more sensitive to light and being a more expansive technology ? A friend of mine is a scientist and tells me that in astronomy and industrial applications the reverse of what is going on in the camera business is true, CCD's are more light sensitive and have less noise compared to CMOS. I noticed with most cameras that use CCD's (like the phase backs) anything over 800iso is not really considered to be great. The sensors that go to space are also CCD's.


All MFDBs are CCD (up to now), the P1 P25+ and P45+ are the world leaders in low light because of their ability to keep the sensor cool for long exposures, this is due to the great cooling system not the type of sensor used, the MFDBs are worst in their ISO performance because they lack any kind of noise reduction filter or circuit, this is a choice of the manufacturers due to the demand of the MF market for purity so that low ISO performance is maximum! The IQ of DBs is well beyond any modern DSLR even if they are 5 or 6 years old! The reason for CMOS sensors is mainly the low cost of production, but they do cost a lot more than CCDs to develop. I guess that the production volume of DSLRs compensates for the high development cost of CMOS. CCDs are considered sharper and with greater color than CMOS, I'm not aware which technology is better for high Iso, to compare that we should have a comparison of cameras with both technologies but the same NR system. Regards, Theodoros. www.fotometria.gr

So - in answer to the OP's question, which asked only about high ISO and never once mentioned long exposures, your first explanation connects "low light" with "long exposures". What else were we to think, but that you were confused between them? We can only read it the way you write it.

I still have no idea what my insult was? If an apology is warranted, how can I apologise if I don't know what I'm apologising for?!


Thanks, but I already have a really good job, as a university lecturer in physics and astronomy. I teach a course on signal processing, another on astronomical data analysis, and another on observational astronomy, with a particular emphasis on detector issues. I've been doing digital image processing since 1992; my PhD thesis concerned calibrating astronomical imaging photon-counting detectors called MAMAs, and their use in high-resolution imaging, photometry and deconvolution of the centres of star clusters.

But I guess a British MechEng BEng degree trumps that.

Now I AM annoyed, because you're the first person ever on LuLa to force me to play the "my credentials are better than yours" card, and I really hate doing that. The letters after one's name should have nothing to do with anything in a discussion like this. Only the ability to present proper evidence matters. We're still waiting for yours...

OK! READ IT THE WAY I RIGHT IT!!!!  Shocked I suggest you need some therapy  Grin Excessive CO2 has caused you some very serious brain damage.  Wink  Smiley  Cheesy  Grin Its really a pity for a PHD professor to humiliate himself by his own statements!  Shocked  Roll Eyes There is no person in the world "buddy" that would come in the assumptions that you came by reading what you have up there in bold WHICH IS MY STATEMENT AND THERE IS NOTHING WRONG WITH IT!!  Kiss And please don't try to give me any advice of morality, SINCE ITS YOU THAT "JUMPED" ME WITHOUT ANY REASON WHATSOEVER!!  Huh  Tongue I suggest you stop humiliating yourself and do some photography or read some Aristoteles (The greatest of philosophers and inventor of logic as a science)  Wink  Smiley AH! and open up the window..., fresh air will do you some good....  Cool By the way... there is no DSLR (certainly no Canon) that turns completely its NR off when its instructed to do so from menu  Kiss .....and there is nothing to change that no matter what you think or not.  Cheesy ....and please don't bother me, answer to me, talk to me, refer to me, or think about me anymore!  Grin  Kiss I don't even want your apology for stating that what you have up there in bold is a result of a confused mind! You don't exist for me!  Smiley  Cool www.fotometria.gr
« Last Edit: September 30, 2011, 02:20:41 AM by fotometria gr » Logged
fotometria gr
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« Reply #43 on: September 29, 2011, 07:20:38 PM »
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CCD or CMOS's don't have "greater color". They don't have any color. They count photons. You can filter photons before they reach the CCD, by means of an individual filters or a filter matrix (for example Bayer).

True enough, sensors are really B&W, I guess "considered" is the key word.... Smiley  I'm surprised how you confused "considered" (which refers to the result) with "have",  Shocked ....its really easy to goof between the two words i guess,  Roll Eyes  ....they are so near in grammar and vocabulary that can happen to anybody  Lips sealed  Cool Regards, Theodoros. www.fotometria.gr

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billthecat
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« Reply #44 on: September 29, 2011, 07:22:33 PM »
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I'd think that CCDs have better color since the value of each pixel is more matched to other pixels due to the different readout of CCD vs CMOS.

Bill

CCD or CMOS's don't have "greater color". They don't have any color. They count photons. You can filter photons before they reach the CCD, by means of an individual filters or a filter matrix (for example Bayer).

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madmanchan
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« Reply #45 on: September 29, 2011, 07:53:19 PM »
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I'd think that CCDs have better color since the value of each pixel is more matched to other pixels due to the different readout of CCD vs CMOS.

I don't follow you at all.  Can you please clarify what you mean by this?
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ErikKaffehr
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« Reply #46 on: September 29, 2011, 08:01:25 PM »
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No, that makes no sense at all. But it is quite possible that Phase, Leaf or Hasselblad would have a color grid array with transmission characteristic better matched to studio photography at low ISO compared to say Canon who may have a CGA more optimized at available light photography at high ISO. The same situation may apply to DSLR vendors, too. It is probable that Canon, Nikon and Sony have different CGA charactristics.

Best regards
Erik


I'd think that CCDs have better color since the value of each pixel is more matched to other pixels due to the different readout of CCD vs CMOS.

Bill

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jeremypayne
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« Reply #47 on: September 29, 2011, 08:51:53 PM »
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OK!

I really think you ought to find somewhere else to hang out on the internet.
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Schewe
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« Reply #48 on: September 29, 2011, 09:23:45 PM »
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OK! READ IT THE WAY I WRIGHT IT!!!!  Shocked

So, English isn't your first language? Did you mean "right it"?

Quote
P.S. Does anybody remember the story of the tower of Babel from the bible? I wonder why communication is falling lower and even lower by the day....

Uh...before you get all bent out of shape, maybe you should try multiple translations to see if YOU'VE made an error in translation?

I've read the thread and simply don't see why you are bent out of shape...try less caffeine or maybe change your meds?

We're having a discussion here, no need to get your panties in a bunch, right?
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bjanes
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« Reply #49 on: September 29, 2011, 09:33:43 PM »
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Yup, Nikon are bad boys, but only for long exposures. If you search my posting history, I've often chastised Nikon for this. And also, for the way they subtract a bias level from the RAW, which makes it harder (but not impossible) to measure the readnoise, and impossible to fully subtract bias pattern noise from images like flatfields, which is of course nasty when one then comes to divide by a flatfield...as someone has noted here before, it's mostly the astrophotographers who moan about that!

It's nicely explained by Jerry Lodrigus here; scroll down to points 5, 6 and 7 under the "Nikon" heading.

Canon, emphatically, do not alter their RAW files in long exposures - or short ones, for that matter. Nor do they subtract the bias level. RAW means RAW with them.


Emil and Jerry may be very knowledgeable and careful workers, but a FFT analysis of a 30 second Darkframe from the D3 is shown below and I see no evidence of filtering. Processing was as before: split_cfa in Iris and cropping of the green 1 channel to 300 x 300 px in Iris and analysis by Image J. All NR and dark frame subtraction was turned off. I can supply the raw file and the .fit files to anyone who wants to do their own critique.



Here is the FFT of the same file with the median filter applied with a radius of 4 showing clear cut evidence of filtering:



And here is a PNG of the cropped green 1 channel



Regards,

Bill

« Last Edit: September 29, 2011, 10:10:46 PM by bjanes » Logged
BartvanderWolf
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« Reply #50 on: September 30, 2011, 03:37:56 AM »
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Emil and Jerry may be very knowledgeable and careful workers, but a FFT analysis of a 30 second Darkframe from the D3 is shown below and I see no evidence of filtering.

Hi Bill,

I don't see any evidence of filtering in you sample either. Since I don't have a Nikon I cannot test it, but could it be that higher ISO settings behave different from lower ISOs?

Cheers,
Bart
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ondebanks
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« Reply #51 on: September 30, 2011, 04:09:44 AM »
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Emil and Jerry may be very knowledgeable and careful workers, but a FFT analysis of a 30 second Darkframe from the D3 is shown below and I see no evidence of filtering. Processing was as before: split_cfa in Iris and cropping of the green 1 channel to 300 x 300 px in Iris and analysis by Image J. All NR and dark frame subtraction was turned off. I can supply the raw file and the .fit files to anyone who wants to do their own critique.

Here is the FFT of the same file with the median filter applied with a radius of 4 showing clear cut evidence of filtering:

And here is a PNG of the cropped green 1 channel

Regards,

Bill


Nice work, Bill. Maybe Bart's right and Nikon set it up so that it depends on ISO, or else I guess Nikon must have changed their D3 firmware for the better since Christian Buil did his tests in 2007 which showed the D3 filtering and similarly Bill Claff's tests shown by Emil Martinec for the D3, D300, and D200. If that's the case, then I applaud Nikon! If anyone else has a D3 or indeed any modern Nikon DSLR, I'd love to see if that can be confirmed. And Bill, if you have a chance could you take the exposure time out to say 5 or 10 minutes, and see if it is still ok? And also try at different ISO settings? Thanks.

Ray
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Fine_Art
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« Reply #52 on: September 30, 2011, 04:20:47 AM »
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I'd think that CCDs have better color since the value of each pixel is more matched to other pixels due to the different readout of CCD vs CMOS.

Bill


I think the argument is based on the camera testing at the end of manufacture. It is going to be tested against known images of blue , green, red, for output accuracy. The firmware is set to correct any deviation in the signal. In CMOS the correction is against each pixel. In CCD the conversion of photon to current is against whole rows so the converter is calibrated against 1000s of pixels output. Of course each pixel still has to output the same value so the correction of the color is the same. The accuracy of the signal converter should be much greater in CCD.

« Last Edit: January 11, 2013, 05:21:32 PM by Fine_Art » Logged
PierreVandevenne
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« Reply #53 on: September 30, 2011, 06:36:17 AM »
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True enough, sensors are really B&W, I guess "considered" is the key word.... Smiley  I'm surprised how you confused "considered" (which refers to the result) with "have"

I didn't. But I simply find the foundations upon which you base your many claims to be a bit shaky, if only from a rethorical point of view. "is widely considered" is a sociological assessment rather than sound formal logic starting point. And in fact, to some extent, I agree with some of your statements about NR because a lot of current sensors do at the individual CMOS sensel level something that resembles what used to be a full CCD calibration (I base this opinion on the relatively detailed - but nowhere near what Kodak provides for its scientific sensors - information Sony provides on its sensors - links previously given on this board).

But, assuming your statements contain a tiny bit of truth, it would be nice if you could develop your argument without resorting to considerations about atmospheric composition. In this very thread, ondebanks and I slightly disagreed - have you noticed that neither of us ended up attempting to ridicule the other and that both of us presented verifiable arguments? Is that something you would consider? Disagreement, and particularly disagreement about the spoken or written word, is typical of us humans. Learn to live with it and accept, when the object of the discussion is amenable to experimental investigations, that demonstrations/experimentation are better than aggressive discourse.

Last but not least, try to be modest in your claims. About 15 years ago, I build a CCD camera and programmed its firmware from scratch (and litterature, of course, I did not invent the thing). At that time, I certainly felt that I knew a lot about how sensors worked. Today is a very different era in sensing techonology and, except for people who devote their whole life to a specific sub-area of this immense topic, no one can claim to know everything that goes on under the bonnet.

AFAIC, even if I don't always agree 100% with a competent person (such as Emil, Ondebanks, Bart and many others), I am grateful for what they share and I see the eventual friction points between what they say or write and what I think as opportunities to improve my understanding.
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madmanchan
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« Reply #54 on: September 30, 2011, 06:54:10 AM »
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I think the argument is based on the camera testing at the end of manufacture. It is going to be tested against known images of blue , green, red, for output accuracy. The firmware is set to correct any deviation in the signal. In CMOS the correction is against each pixel. In CCD the conversion of photon to current is against whole rows so the converter is calibrated against 1000s of pixels output. Of course each pixel still has to output the same value so the correction of the color is the same. The accuracy of the signal converter should be much greater in CCD.

I think these are minor differences in the big picture. 

By far the biggest factor in the output color response is the spectral transmission of the Bayer color filters.  As far as color reproduction goes (*), I've measured some CCDs with great spectral transmission curves and other CCDs with not-so-great ones.  The same with CMOS sensors. 

Eric

(*) i.e., getting a good match on the so-called Luther-Ives condition
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Daniel Browning
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« Reply #55 on: September 30, 2011, 10:26:47 AM »
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Emil and Jerry may be very knowledgeable and careful workers, but a FFT analysis of a 30 second Darkframe from the D3 is shown below and I see no evidence of filtering.

The only purpose that Nikon intended for the so-called noise reduction is to suppress unmapped hot/dead pixels, so the effect is definitely going to be a lot more subtle than a global median filter. That's why I prefer the astrophotographer's term for it, the "Nikon star killer algorithm." Smiley

A highly talented engineer named Marianne Oelund completed a rather detailed characterization of the algorithm as it was implemented in older Nikon cameras, the D3, and most recently, the D7000:

http://forums.dpreview.com/forums/read.asp?forum=1021&message=34309201

Here is a link to an image demonstrating the star killer effect:

http://actionphotosbymarianne.com/spectra/HPSeffectEx1.jpg
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--Daniel
bjanes
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« Reply #56 on: September 30, 2011, 11:40:57 AM »
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The only purpose that Nikon intended for the so-called noise reduction is to suppress unmapped hot/dead pixels, so the effect is definitely going to be a lot more subtle than a global median filter. That's why I prefer the astrophotographer's term for it, the "Nikon star killer algorithm." Smiley

A highly talented engineer named Marianne Oelund completed a rather detailed characterization of the algorithm as it was implemented in older Nikon cameras, the D3, and most recently, the D7000:

http://forums.dpreview.com/forums/read.asp?forum=1021&message=34309201

Here is a link to an image demonstrating the star killer effect:

http://actionphotosbymarianne.com/spectra/HPSeffectEx1.jpg

Daniel,

Thanks for the links. I did look at them and found them quite interesting. Marianne is truly amazing--it is unfortunate that she does not post on LuLa. Emil did contribute to that thread, and he noted that the effect did not show up on Fourier analysis, so my tests likely were not sufficiently sensitive to detect hot pixel filtering.

Regards,

Bill
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Fine_Art
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« Reply #57 on: September 30, 2011, 03:51:45 PM »
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I think these are minor differences in the big picture. 

By far the biggest factor in the output color response is the spectral transmission of the Bayer color filters.  As far as color reproduction goes (*), I've measured some CCDs with great spectral transmission curves and other CCDs with not-so-great ones.  The same with CMOS sensors. 

Eric

(*) i.e., getting a good match on the so-called Luther-Ives condition

They are small in the sense that all consumer cameras now have very good color reproduction, CCD or CMOS. Its still a consumer product not something made for NASA or a defense department. The tolerance in the parts is a real issue when there is a very competitive market. For example Pentax in the K5 managed to squeeze much more out of the same sensor than Sony, the manufacturer, or Nikon did with their version of the camera. They chose some higher quality part. With CCD row conversion a higher quality signal converter has much more return per part due to it's effect on entire rows.

Maybe you are right that the tolerances of the color filters have much more effect. Anyone know how they degrade over time?
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ErikKaffehr
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« Reply #58 on: September 30, 2011, 04:08:05 PM »
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Hi,

I would leave out NASA, they do a lot of false color work and also a lot of invisible part of electromagnetic spectrum stuff. Also NASA stuff is probably radiation hardened.

The main reason that Sony is lagging Pentax and Nikon may be that their ASIC (Bionz) is 12 bits, while Pentax and Nikon use 14 bits.

If you compare the figures you see that all cameras are essentially on the same line regarding SNR. Pentax has slightly better SNR at high ISO due to raw noise reduction.

DR is worse on the sony, that could be read noise or 12-bitness.

Best regards
Erik




They are small in the sense that all consumer cameras now have very good color reproduction, CCD or CMOS. Its still a consumer product not something made for NASA or a defense department. The tolerance in the parts is a real issue when there is a very competitive market. For example Pentax in the K5 managed to squeeze much more out of the same sensor than Sony, the manufacturer, or Nikon did with their version of the camera. They chose some higher quality part. With CCD row conversion a higher quality signal converter has much more return per part due to it's effect on entire rows.

Maybe you are right that the tolerances of the color filters have much more effect. Anyone know how they degrade over time?
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ondebanks
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« Reply #59 on: September 30, 2011, 07:00:20 PM »
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I would leave out NASA, they do a lot of false color work and also a lot of invisible part of electromagnetic spectrum stuff. Also NASA stuff is probably radiation hardened.

Absolutely. I would be surprised if NASA ever used a stills imager with a CFA, other than "reportage" cameras to document launches and stuff happening on manned missions. Imagers for their astronomy & space science programmes would not want to have a fixed, predetermined colour filtration, which cuts out valuable UV and deep red/IR wavelengths, and where maybe only 1/4 of the pixels are sensitive to what's being measured. I can't speak for every mission, but I've worked a lot with Hubble data and I can guarantee that none of the UV (FOC, STIS), Visible (WF/PC, WFPC2, ACS) or IR (NICMOS) cameras had a CFA.

Ray
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