Luminous Landscape Forum
Equipment & Techniques => Digital Cameras & Shooting Techniques => Topic started by: Bernard ODonovan on September 21, 2010, 07:22:07 am
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Foveon sensor making new progress again, very interesting given the info each pixel provides !
http://www.dpreview.com/news/1009/10092129sigmasd1.asp
(http://a.img-dpreview.com/news/1009/sigma/SD1-001.jpg)
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http://www.luminous-landscape.com/essays/mark_dubovoys_photokina_blog.shtml
;)
DaveL
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Some views of it in hand
http://www.youtube.com/watch?v=ZeCDdm7X9T4
http://www.youtube.com/watch?v=pIFrQUCJitI
So not finalised yet. No mention of RAW depth, they appear to be 12 bit on previous Sigma's. Could get Video.
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In a full frame format, this Foveon sensor design would put out over 100M derived pixels with current technology. I'd like to see that! Sigma should make and show off a prototype.
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In a full frame format, this Foveon sensor design would put out over 100M derived pixels with current technology. I'd like to see that! Sigma should make and show off a prototype.
Any signs that it has accurate colors?
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Any signs that it has accurate colors?
It looks like the same technology is being used (color channel separation by silicon penetration depth), so reconstructing the colors remains problematic. Software has to work with whatever the hardware delivers, and we know that the saturation of the channels needs a significant bump. It should be able to deliver good monochromatic results though, if the Rawconverter can bypass some of the color boosting steps.
Compared to the SD15, the sensel pitch has been reduced from 7.84 micron down to 5 micron, 41% of the potential area in square microns. That won't help the photon statistics, high ISO will probably remain an issue. The smaller sensel pitch will reduce the aliasing tendency a bit, but dynamic range may be stressed by the reduced well capacity.
So we'll still have to wait for some real images and see.
Cheers,
Bart
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It looks like the same technology is being used (color channel separation by silicon penetration depth), so reconstructing the colors remains problematic.
I couldn't agree more ; in particular, some weird (apparently random from my very limited tests with DP1 raws) color shifts in the shadows were problematic with the previous versions.
That said, it wouldn't be fair to dismiss any potential progress with the technology! Who would have thought back in 2000 that diminishing the pixel pitch of (Bayer ;) ) CMOS sensors would yield such an IQ?
So we'll still have to wait for some real images and see.
And particularly, real raw files.
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Actually color is a known weakness of the foveon sensor. Joseph Wisniewski has some nice posts on the subject in the DPReview forum.
Resolution is the foveon's strength. Particularly this camera.
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Actually color is a known weakness of the foveon sensor. Joseph Wisniewski has some nice posts on the subject in the DPReview forum.
What do you mean color is a weakness? If you mean accuracy, Velvia nor Kodachrome are accurate yet they defined generations of photography.
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What do you mean color is a weakness? If you mean accuracy, Velvia nor Kodachrome are accurate yet they defined generations of photography.
Okay.
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Yes and no IMO. Color in the "confort zone" is not a problem, pretty much exceptional I would say, except in some shadows generally indoor, but that can be recuperate easily in PP.
Resolution is and has never been the strengh of the Foveon. Michael Reichmann's articles about came to a similar conclusion: it is not 3 times but more 2 times the Sigma claims. You can extract the full potential, true, but to a post-prod manipulation AND with the proper equipment, wich meand time and skills are required.
This fact has been discusted and demostrate many times in the Sigma users forums and there is a clear consensus about that since the SD14 and DP1. My personal experience with both cameras tells me the same.
I'm surprised to hear that about the Foveon resolution. If I have time I'll read the Wisniewski's articles to see what he means.
It seems like 2x the resolution of bayer at the same number of pixels would be a strength. Not being able to get as many pixels on there (until now) would be a weakness.
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Okay.
Now I get your sig...
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Now I get your sig...
It took you that long? You ask me a question, predicted the response and responded to that. What response were you expecting from me?
BTW, just ran across this comment from Eric Fossum on foveon...
"Indeed, the spectral response of the silicon 3-layer structure is fundamentally different from the human eye's response. It is only thru massive computing that the color comes out as well as it does. To me the color quality of the Foveon-type sensor is right there with a 747 leaving the ground in terms of technical amazement. " (http://forums.dpreview.com/forums/read.asp?forum=1000&message=36411196)
Edit: Fossum quote added because I find it funny. Not as a comment on the quality of the foveon colors. It does suggest Fred is right that one wants to stay within the foveon's comfort zone.
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Resolution is and has never been the strengh of the Foveon.
It's more a question of acutance imho, so proper sharpening could level a bit that ground.
That said, there is some luminance Moiré doing a really nice trick to disguise itself into very fine random detail, too.
IMHO, it may be a real strength, until you enlarge too much and end enlarging those artifacts.
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http://dpreview.com/news/1010/10100504Sigmainterview.asp (http://dpreview.com/news/1010/10100504Sigmainterview.asp)
Interesting exchange.
Confirmation no video for the SD1
This could be a good one...
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I will buy an SD1 if its imager performance is in the same bracket as my DP1, or better. I always found the pixel level appearance of shots with the DP1 to be superior to virtually anything else, it just lacked for ultimate resolution, and around 30mp bayer equivalence would make it a compelling choice. It won't replace my H4D-50, of course, but it may give my Sony A900 a run for its money.
Quentin
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I will buy an SD1 if its imager performance is in the same bracket as my DP1, or better. I always found the pixel level appearance of shots with the DP1 to be superior to virtually anything else, it just lacked for ultimate resolution, and around 30mp bayer equivalence would make it a compelling choice. It won't replace my H4D-50, of course, but it may give my Sony A900 a run for its money.
Have you tried downsampling your A900 6048 x 4032 pixel images down to 4800 × 3200 with the Nearest Neighbor resampling method in Photoshop? That should give a reasonable impression of what can be expected.
Nearest Neighbor downsampling + sharpening will produce a similar 'crispness' compared to a sensor array without AA-filter. You can verify that by downsampling to 2640 x 1760 pixels and comparing to your DP1 images. It will also reduce the need to invest in new lenses.
Images with a given number of RGB pixels will not magically have a higher resolution of similar to an image with a larger number of pixels. The number of RGB pixels determines the resolution. What can be different is the MTF response at the limiting resolution, but with it comes the tendency for aliasing artifacts.
Cheers,
Bart
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Have you tried downsampling your A900 6048 x 4032 pixel images down to 4800 × 3200 with the Nearest Neighbor resampling method in Photoshop? That should give a reasonable impression of what can be expected.
Nearest Neighbor downsampling + sharpening will produce a similar 'crispness' compared to a sensor array without AA-filter. You can verify that by downsampling to 2640 x 1760 pixels and comparing to your DP1 images. It will also reduce the need to invest in new lenses.
Images with a given number of RGB pixels will not magically have a higher resolution of similar to an image with a larger number of pixels. The number of RGB pixels determines the resolution. What can be different is the MTF response at the limiting resolution, but with it comes the tendency for aliasing artifacts.
Cheers,
Bart
I just downsized my a850 as per your suggestion. I'm sorry, I fail to see any benefit at all. I think, as my friends Click and Clack would say, "BOGGUUSS."
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I just downsized my a850 as per your suggestion. I'm sorry, I fail to see any benefit at all.
Hi Bob,
I didn't say it would be a benefit, but it should create a similar crispness. Care to show us a side by side example of a downsampled/sharpened shot versus a DP1, an interesting crop with detail would do?
Cheers,
Bart
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Hi Bob,
I didn't say it would be a benefit, but it should create a similar crispness. Care to show us a side by side example of a downsampled/sharpened shot versus a DP1, an interesting crop with detail would do?
Cheers,
Bart
you can do that yourself
.X3F raw files for DP1 are available @ http://www.imaging-resource.com/PRODS/DP1/DP1THMB.HTM
similar () scenes (raw files) from 24mp FF cameras are available on the same website.
not bad for 4.6mp sensor
http://img715.imageshack.us/img715/6069/dp1hsli100.jpg
now imagine that you will be dealing with 15.4mp one.
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you can do that yourself
I know, that's why I wondered if Bob had, and how he came to his conclusion ...
When I downsample an A900 image, even with just regular bicubic resampling (which is not optimal either), I get a much better image quality than the DP1 produces at its native resolution (which should be very obvious due to the amount of oversampling, less so with the larger pixel count of the SD1). Maybe my Photoshop does something different than Bob's, or he has a different example which reacts differently to downsampling?
Cheers,
Bart
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I know, that's why I wondered if Bob had, and how he came to his conclusion ...
When I downsample an A900 image, even with just regular bicubic resampling (which is not optimal either), I get a much better image quality than the DP1 produces at its native resolution (which should be very obvious due to the amount of oversampling, less so with the larger pixel count of the SD1). Maybe my Photoshop does something different than Bob's, or he has a different example which reacts differently to downsampling?
Cheers,
Bart
don't you think that you need to take
4.6mp * (24mp / 15.4mp) = 7.2mp camera to compare something with DP1 ? do you think that if you will downsample your 7.2mp camera it will beat 4.6mp of DP1 ? in the absence of 7.2mp cameras we can try 8mp Canons like Canon 30D ( http://www.imaging-resource.com/PRODS/E30D/E30DhSLI0100.CR2.HTM ) ;)
here is the Canon 8mp downsampled ("Nearest Neighbor", CS5) to DP1 ( 2640 x 1760 )
http://img217.imageshack.us/img217/3576/e30dhsli0100.jpg
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don't you think that you need to take
4.6mp * (24mp / 15.4mp) = 7.2mp camera to compare something with DP1 ? do you think that if you will downsample your 7.2mp camera it will beat 4.6mp of DP1 ? in the absence of 7.2mp cameras we can try 8mp Canons like Canon 30D ( http://www.imaging-resource.com/PRODS/E30D/E30DhSLI0100.CR2.HTM ) ;)
here is the Canon 8mp downsampled ("Nearest Neighbor", CS5) to DP1 ( 2640 x 1760 )
http://img217.imageshack.us/img217/3576/e30dhsli0100.jpg
I'm not sure why you chose Nearest Neighbor as the downsampling method, as it produces unfairly poor results. Using the recommended Bicubic Sharper method the results are much better. Even then the DP1 is still significantly sharper - very impressive. Can't wait until the new Sigma is released to see if it retains the same per-pixel IQ.
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I'm not sure why you chose Nearest Neighbor as the downsampling method
That was suggested by BartvanderWolf, not by me as the way to get the similar visual qualify (@ 100% on screen) from existing 24.4mp (6048 x 4032) bayer w/ AA as in planned 15.4mp (4800 x 3200) foveon in SD1... I was just trying to show that this way (Nearest Neighbor) does not work even for 8.2mp (3504 x 2336) bayer vs 4.6mp (2640 x 1760) foveon and 8.2 / 4.6 is > than 24.4 / 15.4... certainly if we will start to cheat by printing (and not pixel peep) it might be another story.
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certainly if we will start to cheat by printing (and not pixel peep) it might be another story.
That's funny! The idea that it is cheating to examine images the way that they are actually going to be viewed anywhere outside forum debates, and instead the honest approach is to take a tiny fraction of the image (say 2MP out of 15MP or more), blow that fragment up to about the size of a 19"x13" print (23" monitor) at a pathetically low resolution of about 100ppi, without even using upressing as one would if making a serious effort to print so big from so few pixels.
My gut feeling is that, given that such IQ comparisons are likely to be made by looking from as close as the viewer can comfortably focus, no display resolution under about 200PPI is of much relevance as a predictor of how the final displayed images will look to the "end user". Lower res. like 150PPI can work well in practice for large prints, say 19"x13" and up, but only to the extent that such prints are viewed from a comfortable distance, 15" or more, not at "print sniffing" range.
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That's funny! The idea that it is cheating to examine images the way that they are actually going to be viewed anywhere outside forum debates
most of the world population do not view their images printed nowadays... you might not like it, but at best they view them resized, etc... and it is very easy for them to zoom exactly 100% at particular interesting part of the image, unlike with the printed image... and even those who print do not print everything that they still keep and look at occasionally.
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If it's true that prints no longer matter (or soon won't), it seems pointless to build sensors with more than 3-4 mpix, given that most monitors don't display more than about 2 megapixels or so. Actually then, two mpix would be enough but I am allowing for the occasional need to crop, even though that's frowned on by some. But maybe I'm missing the point. Maybe it's not about looking at pictures anymore.
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most of the world population do not view their images printed nowadays
Agreed on that; but those who view mostly or entirely on-screen also mostly view at about 2MP, needing at most about a 4MP sensor with a Bayer CFA. I doubt that most screen viewers (outside of us forum geeks) care much about scrutinizing crops to 20% or less of the total image area.
P. S. I just read Robert Roaldi's reply: I could have left it at that!
P.P.S There is none thing that screen viewing can reveal but prints miss: dynamic range, which is rather pathetic in prints. That is why about 200PPI or "50%" on screen makes sense to me for assessing IQ, which allows significant zooming in to only part of the image.
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If it's true that prints no longer matter (or soon won't), it seems pointless to build sensors with more than 3-4 mpix, given that most monitors don't display more than about 2 megapixels or so. Actually then, two mpix would be enough but I am allowing for the occasional need to crop, even though that's frowned on by some. But maybe I'm missing the point. Maybe it's not about looking at pictures anymore.
certainly you are missing the point - people do zoom and look at certain parts of the image @100%... and they can do that w/ one click...
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Have you tried downsampling your A900 6048 x 4032 pixel images down to 4800 × 3200 with the Nearest Neighbor resampling method in Photoshop? That should give a reasonable impression of what can be expected.
Nearest neighbor downsampling should give you:
1. A very "sharp" aliased image
2. No noise suppression
I dont see the relevance of using that kind of resampling for comparing a high-resolution to a low-resolution camera. I'd rather use something that:
1. Does some spatial averaging (reduces noise and aliasing)
2. Coefficients could either be equal (rectangular filter) to simulate larger pixel sites, or somewhat smoothened to simulate lower cutoff OLPF
3. Allow negative coefficients or only positive? That depends. A camera sensor + optics will only have positive coefficients, so for simulating that you should have no negatives. But one benefit of having a high-rez sensor is that you can do processing in software instead of hardware...
I think that is more fair to the high-resolution camera. Now, I guess it all depends on what one wants to compare, and this comparision may tend to be an apples and oranges one.
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Nearest neighbor downsampling should give you:
1. A very "sharp" aliased image
2. No noise suppression
I dont see the relevance of using that kind of resampling for comparing a high-resolution to a low-resolution camera.
While downsampling with the nearest neighbor method is certainly suboptimal (as I've demonstrated here (http://www.xs4all.nl/~bvdwolf/main/foto/down_sample/down_sample.htm)), it is a quick and dirty method to visualize aliasing artifacts of a camera without optical low-pass filter (OLPF) without the risk of false color demosaicing. It is not going to give exactly the same result as the Foveon sensor will produce, but it does create a sharpness/crispness that's somewhat similar, and which seems to be in a large part the appeal of Foveon images to many observers.
I've attempted to keep the suggested approximation method simple, so others with modest means can individually reproduce the effects. One can certainly create a more elaborate/accurate approximation by using a different downsampling method/filter but that seems a bit of overkill, and may give the larger image an 'unfair' benefit. Afterall, significant oversampling and optimized downsampling is in most cases going to give better results than sampling at a lower frequency (plus upsampling) without OLPF.
Cheers,
Bart
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While downsampling with the nearest neighbor method is certainly suboptimal (as I've demonstrated here (http://www.xs4all.nl/~bvdwolf/main/foto/down_sample/down_sample.htm)), it is a quick and dirty method to visualize aliasing artifacts of a camera without optical low-pass filter (OLPF) without the risk of false color demosaicing. It is not going to give exactly the same result as the Foveon sensor will produce, but it does create a sharpness/crispness that's somewhat similar, and which seems to be in a large part the appeal of Foveon images to many observers.
I see that you are trying to help people do this for themselves.
But in the interest of doing it "right" (even if that makes it less accessible), I would suggest the following:
A OLPF-less Foveon sensor should (ideally) integrate an unweighted area of dimensions NxM and sample the photon count. We would like to see what that leads to in terms of IQ,
1. Find a good high-resolution image with pleny of details up to the Nyquist limit, but few debayering artifacts or moire.
2. Optionally, do image blurring (using e.g. Gaussian blur)
3. Do a integer decimation of either 2x2, 3x3 etc by averaging a neighborhood
By doing/not doing step 2, one could get an idea of what the benefit/drawback of OLPF would be for a Foveon sensor.
Of course, this depends on a range of idealised models. I assume that the accumulated blurring from motion-blur, optics and OLPF might as well be modelled by a Gaussian, but real-life may not be that simple.
I think that adhering to/breaking the Shannon-Nyquist sampling theory can be explained (somewhat exaggerated) by the following analogy:
When using a topography map to navigate the terrain. Would you rather that each elevation reading represented:
A) An infinitely small point in the centre of each square
B) A flat average covering exactly the representation square
C) A weighted average that is most depending on the center value, less to the edges of the square, but also of values outside the square
A) Means no prefiltering, maximum acuteness and maximum aliasing/moire. It also cannot be implemented in real sensors. C) can mean optimal sampling in the Nyquist sense, but that cannot be implemented fully in a sensor either. B) Is what ideal OLPF-less Foveon sensors would do, and contains characteristics of both A) and C). OLPF-equipped Foveons would be somewhere between B) and C).
-h
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I will buy an SD1 if its imager performance is in the same bracket as my DP1, or better. I always found the pixel level appearance of shots with the DP1 to be superior to virtually anything else, it just lacked for ultimate resolution, and around 30mp bayer equivalence would make it a compelling choice. It won't replace my H4D-50, of course, but it may give my Sony A900 a run for its money.
Quentin
The funny part is that the new sensor will provide above 30 actual megapixels in a 36 x 24 sensor. Maybe is too late for sigma, or maybe the features are not there. I am inclined to believe that the foveon sensor will give diminishing returns as sensor density increases. But let's way and see.
I eager to see the pictures this sensor can do.