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Bayer sensor and MX
The way the Bayer sensor works, it "makes up" color information depending on
the surrounding pixels. But if you do multiple exposures with exactly the same scene, the picture gets more sharp according to the amount of exposures. Much is due to the fact that noise is distributed randomly and hence, the same place where a "piece" of noise was before, it's over written with data the next exposure. What I was wondering: do the pixel interpolation always work the same way? Or is this also slightly random (shifting)? So do you, in fact, get more information or only less noise? It just seems hard to believe, that every take of a picture would give exactly (I mean pixel deep peeping) the same result. And also: do all Bayer sensor work exactly the same, or is there a difference in Nikon, Canon, older, newer models? -- Sosumi |
#2
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Bayer sensor and MX
On Feb 8, 5:16 pm, "Sosumi" wrote:
The way the Bayer sensor works, it "makes up" color information depending on the surrounding pixels. But if you do multiple exposures with exactly the same scene, the picture gets more sharp according to the amount of exposures. Much is due to the fact that noise is distributed randomly and hence, the same place where a "piece" of noise was before, it's over written with data the next exposure. What I was wondering: do the pixel interpolation always work the same way? Or is this also slightly random (shifting)? I haven't heard of algorithms using such an approach. Here's a survey of the field: http://citeseer.ist.psu.edu/cache/pa...mosaicking.pdf or if you prefer http://preview.tinyurl.com/2qo63e (you can just skip to the photographs if you want, there's a good range of the various errors that can be introduced by demosaicing algorithms). So do you, in fact, get more information or only less noise? It just seems hard to believe, that every take of a picture would give exactly (I mean pixel deep peeping) the same result. Aside from various kinds of noise, why is it surprising? |
#3
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Bayer sensor and MX
Sosumi wrote:
What I was wondering: do the pixel interpolation always work the same way? Ask Mr.G about Drizzle Algorithm, such as http://www.astrosurf.com/buil/iris/t...2/doc12_us.htm Don't forget that Drizzle is adapted only to undersampled images -- Frédéric |
#4
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Bayer sensor and MX
"Sosumi" schreef in bericht ... The way the Bayer sensor works, it "makes up" color information depending on the surrounding pixels. But if you do multiple exposures with exactly the same scene, the picture gets more sharp according to the amount of exposures. No the picture does not get more sharp. If there is a lot of noise in one normal picture, the definition of the picture get's a littlebit better, but for most normal pictures (in normal light) taking more pictures of the same scene does not make it sharper. In theory small movements of the camera and adjusting for these movements when adding the pictures, will give a better picture and less risc of moire. In theory this method can even make pictures sharper, but then you need a very large amount of the 'same' pictures to get the pictures noticeble sharper. Much is due to the fact that noise is distributed randomly and hence, the same place where a "piece" of noise was before, it's over written with data the next exposure. Multiple pictures will reduce the noice, but with correctly exposed pictures there is not a lot of noise. (Long exposure pictures will benefit from multiple exposure, but not normally exposed pictures). What I was wondering: do the pixel interpolation always work the same way? Or is this also slightly random (shifting)? So do you, in fact, get more information or only less noise? It just seems hard to believe, that every take of a picture would give exactly (I mean pixel deep peeping) the same result. And also: do all Bayer sensor work exactly the same, or is there a difference in Nikon, Canon, older, newer models? There are some variations. Most sensors have 2 greens, 1 red and 1 blue for every four cells in a square. There are sensors where the second green is replace by another color. There are sensors which are not RGB, but YMC, but I haven's seen them them lately in camera's. Normal Bayer sensors GRGRGRGR BGBGBGBG GRGRGRGR BGBGBGBG Interpolation which is most simple is that, on each pixel Green pixel (position). Green = G (from the pixel) Red= (Rl+Rr)/2 from the left and the right Bleu = (Bu+Bd)/2 from the up and down bleu. Red pixel (position). Green = (Gl+Gr+Gu+Gd)/4 Red = R (from the pixel) Bleu = (B+B+B+B)/4 from the 4 corners of R Bleu pixel (position). Green = (Gl+Gr+Gu+Gd)/4 Red = (R+R+R+R) /4 from the 4 corners of B Bleu = B (from the pixel) This is without sharpening or any other fancy stuf. (In general sharpening subtracts a little bit of pixels laying further away). When using multiple exposure with shifted pixels, something similar is done, with far smaller pixels, where the 'large' pixels are shifted over the small pixels. Using sharpening this will result in a slightly sharper picture. As you can see the Red and Bleu pixels (positions) get the information of the Bleu and Red colors from quite some distance. The resolution for red only or bleu only is significant less than for black and white. ben -- Sosumi |
#5
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Bayer sensor and MX
On Feb 8, 9:10 pm, Fred wrote:
Sosumi wrote: What I was wondering: do the pixel interpolation always work the same way? Ask Mr.G about Drizzle Algorithm, such ashttp://www.astrosurf.com/buil/iris/tutorial2/doc12_us.htm Don't forget that Drizzle is adapted only to undersampled images But that is quite different: it exploits shifts in the input images to increase the spatial sampling rate, as opposed to using an interpolation that has a stochastic element. No? |
#6
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Bayer sensor and MX
In article , Sosumi
wrote: The way the Bayer sensor works, it "makes up" color information depending on the surrounding pixels. it doesn't 'make up' colour information, it uses multiple pixels to calculate it. And also: do all Bayer sensor work exactly the same, or is there a difference in Nikon, Canon, older, newer models? the specific demosaic algorithm used will be different, just as there are differences among different raw converters. also, newer cameras may have a better algorithms than older ones. |
#7
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Bayer sensor and MX
"ben brugman" wrote in message bel.net... "Sosumi" schreef in bericht ... The way the Bayer sensor works, it "makes up" color information depending on the surrounding pixels. But if you do multiple exposures with exactly the same scene, the picture gets more sharp according to the amount of exposures. No the picture does not get more sharp. If there is a lot of noise in one normal picture, the definition of the picture get's a littlebit better, but for most normal pictures (in normal light) taking more pictures of the same scene does not make it sharper. You're wrong. I took several pictures and the more MX times, the sharper the picture. Less noise is sharper. If you blow the pictures up to 100% you clearly see normal noise, grain or pixels, while with the MX pixtures, pixels are hardly visible: it's much smoother. In theory small movements of the camera and adjusting for these movements when adding the pictures, will give a better picture and less risc of moire. In theory this method can even make pictures sharper, but then you need a very large amount of the 'same' pictures to get the pictures noticeble sharper. With 5 -10 exposures on one picture the differense is already very noticeable. Much is due to the fact that noise is distributed randomly and hence, the same place where a "piece" of noise was before, it's over written with data the next exposure. Multiple pictures will reduce the noice, but with correctly exposed pictures there is not a lot of noise. (Long exposure pictures will benefit from multiple exposure, but not normally exposed pictures). No, you're wrong. See above. What I was wondering: do the pixel interpolation always work the same way? Or is this also slightly random (shifting)? So do you, in fact, get more information or only less noise? It just seems hard to believe, that every take of a picture would give exactly (I mean pixel deep peeping) the same result. And also: do all Bayer sensor work exactly the same, or is there a difference in Nikon, Canon, older, newer models? There are some variations. Most sensors have 2 greens, 1 red and 1 blue for every four cells in a square. There are sensors where the second green is replace by another color. There are sensors which are not RGB, but YMC, but I haven's seen them them lately in camera's. Normal Bayer sensors GRGRGRGR BGBGBGBG GRGRGRGR BGBGBGBG Interpolation which is most simple is that, on each pixel Green pixel (position). Green = G (from the pixel) Red= (Rl+Rr)/2 from the left and the right Bleu = (Bu+Bd)/2 from the up and down bleu. Red pixel (position). Green = (Gl+Gr+Gu+Gd)/4 Red = R (from the pixel) Bleu = (B+B+B+B)/4 from the 4 corners of R Bleu pixel (position). Green = (Gl+Gr+Gu+Gd)/4 Red = (R+R+R+R) /4 from the 4 corners of B Bleu = B (from the pixel) This is without sharpening or any other fancy stuf. (In general sharpening subtracts a little bit of pixels laying further away). When using multiple exposure with shifted pixels, something similar is done, with far smaller pixels, where the 'large' pixels are shifted over the small pixels. Using sharpening this will result in a slightly sharper picture. As you can see the Red and Bleu pixels (positions) get the information of the Bleu and Red colors from quite some distance. The resolution for red only or bleu only is significant less than for black and white. ben -- Sosumi |
#8
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Bayer sensor and MX
Sosumi wrote:
You're wrong. I took several pictures and the more MX times, the sharper the picture. Less noise is sharper. If you blow the pictures up to 100% you clearly see normal noise, grain or pixels, while with the MX pixtures, pixels are hardly visible: it's much smoother. No... you're wrong. It doesn't get sharper, it simply reduces the noise. Less noise isn't "sharper", it's "less noise". You are increasing the signal to noise ratio. With 5 -10 exposures on one picture the differense is already very noticeable. Multiple exposure blending reduces noise by a known and mathematically demonstrable amount. Three exposures doubles the signal-to-noise ratio. Nine exposures triples it. -- Jeremy Nixon | address in header is valid (formerly ) http://www.flickr.com/photos/100mph/ |
#9
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Bayer sensor and MX
On Feb 9, 3:07 am, Jeremy Nixon ~$!~( )@( )u.defocus.net wrote:
Sosumi wrote: You're wrong. I took several pictures and the more MX times, the sharper the picture. Less noise is sharper. If you blow the pictures up to 100% you clearly see normal noise, grain or pixels, while with the MX pixtures, pixels are hardly visible: it's much smoother. No... you're wrong. It doesn't get sharper, it simply reduces the noise. Less noise isn't "sharper", it's "less noise". You are increasing the signal to noise ratio. With 5 -10 exposures on one picture the differense is already very noticeable. Multiple exposure blending reduces noise by a known and mathematically demonstrable amount. Three exposures doubles the signal-to-noise ratio. Nine exposures triples it. I'd say that four exposures double S/N, etc. No? Anyway I think we're all wasting our time (unless someone reading this thread later finds some of the replies interesting). It looks like the OP is just stupidly attacking (and not for the first time). |
#10
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Bayer sensor and MX
Thanks Ben for a nice clear explanation. This can be really effective
for astronomy but that is pushing the limits so far beyond normal photography. For astro work they make amazing cameras for astounding prices, extra high performance, but I have *never* heard of anyone using those cameras for conventional photography because it just doesn't matter. If it mattered, you would see someone using those $13,000 cooled high performance scientific cameras for advertising diamonds or sports or Hollywood movies or something but nobody does. ben brugman wrote: "Sosumi" schreef in bericht ... The way the Bayer sensor works, it "makes up" color information depending on the surrounding pixels. But if you do multiple exposures with exactly the same scene, the picture gets more sharp according to the amount of exposures. No the picture does not get more sharp. If there is a lot of noise in one normal picture, the definition of the picture get's a littlebit better, but for most normal pictures (in normal light) taking more pictures of the same scene does not make it sharper. In theory small movements of the camera and adjusting for these movements when adding the pictures, will give a better picture and less risc of moire. In theory this method can even make pictures sharper, but then you need a very large amount of the 'same' pictures to get the pictures noticeble sharper. Much is due to the fact that noise is distributed randomly and hence, the same place where a "piece" of noise was before, it's over written with data the next exposure. Multiple pictures will reduce the noice, but with correctly exposed pictures there is not a lot of noise. (Long exposure pictures will benefit from multiple exposure, but not normally exposed pictures). What I was wondering: do the pixel interpolation always work the same way? Or is this also slightly random (shifting)? So do you, in fact, get more information or only less noise? It just seems hard to believe, that every take of a picture would give exactly (I mean pixel deep peeping) the same result. And also: do all Bayer sensor work exactly the same, or is there a difference in Nikon, Canon, older, newer models? There are some variations. Most sensors have 2 greens, 1 red and 1 blue for every four cells in a square. There are sensors where the second green is replace by another color. There are sensors which are not RGB, but YMC, but I haven's seen them them lately in camera's. Normal Bayer sensors GRGRGRGR BGBGBGBG GRGRGRGR BGBGBGBG Interpolation which is most simple is that, on each pixel Green pixel (position). Green = G (from the pixel) Red= (Rl+Rr)/2 from the left and the right Bleu = (Bu+Bd)/2 from the up and down bleu. Red pixel (position). Green = (Gl+Gr+Gu+Gd)/4 Red = R (from the pixel) Bleu = (B+B+B+B)/4 from the 4 corners of R Bleu pixel (position). Green = (Gl+Gr+Gu+Gd)/4 Red = (R+R+R+R) /4 from the 4 corners of B Bleu = B (from the pixel) This is without sharpening or any other fancy stuf. (In general sharpening subtracts a little bit of pixels laying further away). When using multiple exposure with shifted pixels, something similar is done, with far smaller pixels, where the 'large' pixels are shifted over the small pixels. Using sharpening this will result in a slightly sharper picture. As you can see the Red and Bleu pixels (positions) get the information of the Bleu and Red colors from quite some distance. The resolution for red only or bleu only is significant less than for black and white. |
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