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Author Topic: What chance has Sigma's SD1?  (Read 51632 times)

uaiomex

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Re: What chance has Sigma's SD1?
« Reply #100 on: May 29, 2011, 01:41:08 pm »

I like your name 24X36, honoring the only true full frame sensor up to this date. All others are some sort of FF just because they were shrunk to accommodate the then new incipient technology.
If Nikon had bought the Foveon technology and developed according to his capabilities, I just imagine the tete a tete with Canon and now with Sony!
Sigma hasn't been of much help for this technology. Too many drawbacks. Sigma should seek big-time investors and sell sensors like Sony do.
Eduardo


http://www.luminous-landscape.com/tutorials/resolution.shtml



I was actually also kind of bummed when Sigma bought the Foveon technology, since it locks up the product in a minority lens mount from a small-time manufacturer that simply isn't going to make the best use of it. I agree that we would probably see much more enticing offerings with this sensor technology (and that some of the issues with it would have a much better chance of being resolved - pardon the pun) in the hands of the "Big Two." Sigma's price selection for this camera has turned the whole thing into something of a freak show, and their reasoning for the justification of the price is a joke.
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hjulenissen

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Re: What chance has Sigma's SD1?
« Reply #101 on: May 29, 2011, 03:34:55 pm »

Theoretically, Foveon sensors have the potential for 3 times the resolution of a Bayer pattern sensor when both sensors are of equal size. ...
According to what theory, and what kind of resolution? Foveon for certain does not generally have the potential for 3x the number of lp/ph for monochrome input. For most applications (such as human viewers), the luminance resolution is by far the most important one.

-h
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24x36

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Re: What chance has Sigma's SD1?
« Reply #102 on: May 30, 2011, 12:21:19 am »

I like your name 24X36, honoring the only true full frame sensor up to this date. All others are some sort of FF just because they were shrunk to accommodate the then new incipient technology.

Eduardo



Thanks. :)

I've always disliked the "digital shrinkage" of formats to deal with issues of cost, and the attempt to pass the shrinkage off as an "advantage," though I have to admit the marketing people did do a heck of a job with that (the legions that parrot the marketing campaigns as gospel speaks volumes of their success in that regard). I'd like to see more effort focused (pardon the pun) on making larger imaging chips with lower cost and higher yield (which go hand-in-hand, of course), so that all of the formats can be restored to their actual film equivalents.
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feppe

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Re: What chance has Sigma's SD1?
« Reply #103 on: May 30, 2011, 04:34:32 am »

I'd like to see more effort focused (pardon the pun) on making larger imaging chips with lower cost and higher yield (which go hand-in-hand, of course), so that all of the formats can be restored to their actual film equivalents.

Given laws of economics and physics, those efforts will also benefit smaller sensors. And given the mathematics involved, they benefit smaller sensors more than larger ones - ie. improving yields of larger sensors by 10% will improve yields of smaller sensors by >10%.

hjulenissen

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Re: What chance has Sigma's SD1?
« Reply #104 on: May 30, 2011, 06:34:48 am »

Thanks. :)

I've always disliked the "digital shrinkage" of formats to deal with issues of cost, and the attempt to pass the shrinkage off as an "advantage," though I have to admit the marketing people did do a heck of a job with that (the legions that parrot the marketing campaigns as gospel speaks volumes of their success in that regard). I'd like to see more effort focused (pardon the pun) on making larger imaging chips with lower cost and higher yield (which go hand-in-hand, of course), so that all of the formats can be restored to their actual film equivalents.
Do you believe that the 24x36 format is some sort of technology-independent ideal size, or that it simply is what made for economic, portable, high-quality end-results in the film era? If bigger is better, why stop at 24x36? It seems to me that at least part of the reason why 24x36 was so popular was due to limitations in the film medium that cannot be directly transferred to digital.

Or are you argueing more pragmatically based on availablility of lenses (and their "sweetspot"), the ability of people to learn how many mm are needed for "wide angle" etc?

-h
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EsbenHR

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Re: What chance has Sigma's SD1?
« Reply #105 on: May 30, 2011, 08:18:11 am »

Given laws of economics and physics, those efforts will also benefit smaller sensors. And given the mathematics involved, they benefit smaller sensors more than larger ones - ie. improving yields of larger sensors by 10% will improve yields of smaller sensors by >10%.

This is not true.

Let us compute the yield assuming different levels of defects. Let p be the probability of a defect per mm2 of the sensor. The yield is then given by (1-p)A/1mm2, where A is the area of the sensor. (This is simplified but not too far from reality).

Here is a table for different sensor sizes:

Format  AreaYield (p=0.05%)Yield (p=0.01%)Yield (p=0.001%)
IQ180   2169 mm233.8%80.5%97.9%
35mm    864 mm264.9%91.7%99.1%
Nikon DX372 mm283.0%96.3%99.6%
1/1.8   38 mm298.1%99.6%99.9%

Clearly, larger formats gets more competitive with smaller formats if the yield can be improved. Going from a yield of 98% to 100% is not nearly as big as an improvement as going from 34% to 98% is...
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feppe

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Re: What chance has Sigma's SD1?
« Reply #106 on: May 30, 2011, 09:55:57 am »

Clearly, larger formats gets more competitive with smaller formats if the yield can be improved. Going from a yield of 98% to 100% is not nearly as big as an improvement as going from 34% to 98% is...

Thanks for bothering to check my head math, which clearly is inferior to your actual number crunching :)

uaiomex

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Re: What chance has Sigma's SD1?
« Reply #107 on: May 30, 2011, 10:30:24 am »

The beauty of digital sensors is that they can be any size but enormously restrained to legacy glass as well as current lens lines in manufacturing (same thing).
Eduardo

Do you believe that the 24x36 format is some sort of technology-independent ideal size, or that it simply is what made for economic, portable, high-quality end-results in the film era? If bigger is better, why stop at 24x36? It seems to me that at least part of the reason why 24x36 was so popular was due to limitations in the film medium that cannot be directly transferred to digital.

Or are you argueing more pragmatically based on availablility of lenses (and their "sweetspot"), the ability of people to learn how many mm are needed for "wide angle" etc?

-h
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NikoJorj

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Re: What chance has Sigma's SD1?
« Reply #108 on: May 30, 2011, 11:49:24 am »

The resolution limit for APS-C sensors (as respects middle spectrum color) for diffraction-limited lenses at f8-f11 (the range that is a reasonable expectation for mass-produced lenses) is thirteen megapixels for f8, and seven megapixels for f11, based on physics.
And though, one can see a rather small loss of sharpness in photos taken with 18MP APSC sensor @f/11?
Could it be than the presence of an AA filter, and the associated capture sharpening, are able to somewhat offset (or dilute) the loss of sharpness?
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Nicolas from Grenoble
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hjulenissen

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Re: What chance has Sigma's SD1?
« Reply #109 on: May 30, 2011, 01:52:51 pm »

And though, one can see a rather small loss of sharpness in photos taken with 18MP APSC sensor @f/11?
Could it be than the presence of an AA filter, and the associated capture sharpening, are able to somewhat offset (or dilute) the loss of sharpness?
I dont think that the AA filter will ever increase sharpness. Rather, it will decrease sharpness (together with lense/diffraction, pixel count etc).

Capture sharpening can seemingly give arbitrary levels of sharpness if the signal to noise level is sufficient. I dont think that it can ever give arbitrary levels of real details, though.

-h
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ejmartin

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Re: What chance has Sigma's SD1?
« Reply #110 on: May 30, 2011, 02:39:03 pm »

http://www.luminous-landscape.com/tutorials/resolution.shtml

The resolution limit for APS-C sensors (as respects middle spectrum color) for diffraction-limited lenses at f8-f11 (the range that is a reasonable expectation for mass-produced lenses) is thirteen megapixels for f8, and seven megapixels for f11, based on physics. These limits won't be exceeded due to sensor technology, and irrespective of Foveon vs. Bayer "relativity," those maximum resolution limits are here to stay.

Interesting how people throw around numbers without actually looking at test data.  If lenses were really diffraction limited at such apertures, then resolution would not improve with increasing pixel density.  Instead, if on looks at Photozone tests done with 8MP and with 15MP (Canon, Bayer pattern) sensors, one sees a substantial increase in resolution even at f22:

8MP:


15MP:



There is a difference between the point beyond which "diffraction blurs the image more as the aperture shrinks" and the point beyond which "diffraction prevents any further increase in resolution by increasing the pixel density".  The Photozone data shows this quite concretely.  Yes, diffraction decreases the resolution beyond about f8, and yes, increasing pixel density increases resolution even in the regime well beyond f8.

The physics here is that MTF decreases linearly with aperture, but it is not zero at Nyquist for either sensor, and therefore there is a benefit to finer pixel pitch.
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emil

uaiomex

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Re: What chance has Sigma's SD1?
« Reply #111 on: May 30, 2011, 03:44:16 pm »

This is sooo interesting! Thank you Emil for pointing this out. Gimmee more pixels!!!!   ;D
Eduardo

Interesting how people throw around numbers without actually looking at test data.  If lenses were really diffraction limited at such apertures, then resolution would not improve with increasing pixel density.  Instead, if on looks at Photozone tests done with 8MP and with 15MP (Canon, Bayer pattern) sensors, one sees a substantial increase in resolution even at f22:


There is a difference between the point beyond which "diffraction blurs the image more as the aperture shrinks" and the point beyond which "diffraction prevents any further increase in resolution by increasing the pixel density".  The Photozone data shows this quite concretely.  Yes, diffraction decreases the resolution beyond about f8, and yes, increasing pixel density increases resolution even in the regime well beyond f8.

The physics here is that MTF decreases linearly with aperture, but it is not zero at Nyquist for either sensor, and therefore there is a benefit to finer pixel pitch.
« Last Edit: May 30, 2011, 03:46:04 pm by uaiomex »
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NikoJorj

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Re: What chance has Sigma's SD1?
« Reply #112 on: May 30, 2011, 03:50:03 pm »

I dont think that the AA filter will ever increase sharpness.
No, but I'd think it can mask a small loss of sharpness.
Anyway, Emil answerded much better than I did. ;D
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Nicolas from Grenoble
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hjulenissen

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Re: What chance has Sigma's SD1?
« Reply #113 on: May 30, 2011, 04:37:46 pm »

Thank you ej.

I took the liberty of plotting the data that interested me (center resolution) in one common plot. Interesting things happen at the single f/22 measurement point for the 50D. Is this just a measurement error/noise/outlier? The datapoints (sadly) dont overlap, so it could be that my "linearizing" lines are fooling me, and that somewhere between f/16 and f/32, the "diffraction limited" effect kicks in for real. Naiively, one could interpret this as the 50D being more limited by diffraction (on an absolute scale) than the 350D. I do not believe that it is so, nevertheless, some might interpret your data this way.

If you connect two low-order RLC lowpass-filters in series, you should get a total filter response that has lower cutoff frequency than either. If the cutoff frequencies are very different, the lowest one will dominate the output. If the cutoff frequencies are of similar frequency, you will typically see significant changes in the total cutoff by varying the cutoff of either filter. I believe that is what happens here. We are trying to estimate the total system MTF based on simplified cutoff frequencies as if those were "ideal" brickwall lowpass filter. Neither nature nor humans seems to like designing perfect brickwall filters...

Edit:
Added a graph of center sharpness for various macro lenses for FF, 1.6x crop and 2.0x crop. All from photozone. Assuming that one only cares about the maximum center resolution that can be crammed into one single image, and willing/able to adjust distance/focal length freely, bigger sensor AND higher pixel-count seems to be the thing. It seems that increasing the MP count as well as buying a better lense will both typically increase the real center resolution (or the MTF50, at least) up until at least f/16 for 1.6x crop.

In the figure, I have tried to suggest the point of "being diffraction limited" according to http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm . I think it is clear that diffraction starts to limit resolution before this point is reached, and that it continues to pull resolution downwards after this point. So the "diffraction limit" should perhaps serve as a vague guide about where you should venture only with caution, and not an absolute physical brickwall, as it is sometimes described on the interwebs?

-h
« Last Edit: May 30, 2011, 05:56:51 pm by hjulenissen »
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ejmartin

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Re: What chance has Sigma's SD1?
« Reply #114 on: May 30, 2011, 10:25:52 pm »

I suspect the f/32 on the one test is a typo and should be f/22 (or perhaps the other way around).  The data is more consistent if so; the graphs should not cross -- the higher density sensor will never have less resolution due to diffraction.  Perhaps best to compare some other lenses using Photozone tests to make sure.

Edit: Diffraction is a brick wall at some point -- when MTF drops to zero due to diffraction, there is no detail to be found beyond that.  What the graphs show is that current sensors are rather far from this point.  I think what many photographers consider to be "the diffraction limit" is a personal choice on how much diffraction blur they are willing to tolerate on a given system (and as the data shows, the resolution at that point is system dependent).  It's similar to the debates about DR -- there is a quantitative definition of DR, 11-14 stops in current models; and there is the portion of that range that is useful to a given photographer, based on a personal standard of image quality.
« Last Edit: May 31, 2011, 10:02:06 am by ejmartin »
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emil

uaiomex

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Re: What chance has Sigma's SD1?
« Reply #115 on: May 30, 2011, 11:55:30 pm »

Sigma executive apologizes on his twitter page for SD1 price. This is another quake & tsunami for Sigma. This is not funny anymore. I feel sorry for them
Eduardo
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Plekto

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Re: What chance has Sigma's SD1?
« Reply #116 on: May 31, 2011, 04:01:35 am »

Quote
Interesting how people throw around numbers without actually looking at test data.  If lenses were really diffraction limited at such apertures, then resolution would not improve with increasing pixel density.  Instead, if on looks at Photozone tests done with 8MP and with 15MP (Canon, Bayer pattern)...

But the new sensor from Sigma is roughly 15MP - and full-color ones at that. It should do quite well, especially as you open up the lens to F 4.0 and larger.  It will probably easily outclass the typical DSLRs - that is, if you mounted the same glass on the Canon.  But Sigma's glass is *not* a good Zeiss or similar, and that will kill any real advantage.

Better sensor + crappy glass = Good sensor and fantastic glass, in this case.
end result - just get the normal DSLR for a fraction of the price.  Oh, and have 10x the glass to use on it that's any good, that is.

At $2000, Sigma would do some damage.  At what they are charging, it's a toy for yuppies.
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Aku Ankka

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Re: What chance has Sigma's SD1?
« Reply #117 on: May 31, 2011, 05:35:39 am »

But the new sensor from Sigma is roughly 15MP - and full-color ones at that. It should do quite well, especially as you open up the lens to F 4.0 and larger.  It will probably easily outclass the typical DSLRs - that is, if you mounted the same glass on the Canon.  But Sigma's glass is *not* a good Zeiss or similar, and that will kill any real advantage.

If the DSLRs didn't have an AA-filter, the difference in resolving ability between Foveon and Bayer would be quite miniscule with modern demosaicing algorihms. The AA-filter does give some advantage to the Foveon, though how much remains to be seen, as the natural tendency for AA-filters is to weaken with smaller pixel pitches.

(On just about every other metric the traditional sensors easily outdo the SD1 sensor due to the inherit limitations of the technology used in the Foveon.)

Quote
At $2000, Sigma would do some damage.  At what they are charging, it's a toy for yuppies.

At 2k it would sell in similar numbers to what it's predecessors, that is maybe 10-20 thousand units per year. Maybe a bit more due to many upgrades. However it would be very uninteresting to the general public due to it not having all the features of the competition and it not having similar shelf presence, advertisement, peer-pressure network, lens collection and so on while also not having any compelling advantages and having clear disadvantages in image quality as well (color accuracy and noise in color imagery - both unfixable in a sensor of Foveon-like design).

The price they launched sounds like Sigma is about to end their adventure in camera sales and concentrate on their real bussiness, lenses.
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24x36

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Re: What chance has Sigma's SD1?
« Reply #118 on: May 31, 2011, 09:50:56 pm »

Do you believe that the 24x36 format is some sort of technology-independent ideal size, or that it simply is what made for economic, portable, high-quality end-results in the film era? If bigger is better, why stop at 24x36? It seems to me that at least part of the reason why 24x36 was so popular was due to limitations in the film medium that cannot be directly transferred to digital.

Or are you arguing more pragmatically based on availability of lenses (and their "sweetspot"), the ability of people to learn how many mm are needed for "wide angle" etc?

-h

I think the already existing format sizes shouldn't be decreased simply to deal with a fabrication cost issue which is a temporary aspect of a relatively new technology. If someone were to suggest to you that it were a great idea to carry around medium format equipment to shoot on a 24x36 sensor, would you agree with that notion, or dismiss it? That is the same thing, to me, as the idea of carrying equipment sized for a 24x36 format to shoot in a less-than-half-frame format, i.e., APS-C.

I do think 24x36 happens to be the "sweet spot" in terms of size/weight/cost of equipment, and that replacing film with digital sensors does nothing to change that fact. The array of available optics for the 24x36 format is second to nothing, and if digital makes for enhancement of image quality to boot, the more the merrier! If I was a medium format shooter, I'd be just as annoyed about the unwanted/unrequested cropping of my image format as I am using 35mm.

In short, bigger IS better, but there are practical limitations. Ever see a 300-800 zoom for large format? For medium format? Nope! You never will, because nobody could afford one, and you would need a gun motor carriage to transport and use it. I never moved to a larger format because the available tools were too few, never mind the cost of doing so and the logistics of transporting it in the field. Speed is another factor; how many medium or larger format systems can shoot at high frame rates for moving subjects? They are more specialized tools that pose certain limitations as to what the photographer can do. The 35mm format is the format offering the greatest array of tools for the photographer, and the greatest range of capabilities/versatility, while maximizing image quality within the practical constraints of size/weight/cost of equipment. APS-C format is nothing more than a 35mm camera with an undersized sensor, which may reduce cost (mainly of the camera body, as most of the lenses are 35mm anyway) but makes no appreciable dent in size/weight of equipment, and suffers a loss of image quality as well. Furthermore, it suffers (due to the format size reduction) from an unacceptable user interface, i.e., the viewfinders are too small. I found myself unable to focus on anything that wasn't pretty much "infinity" focus with lenses shorter than about 70mm or so with an APS-C viewfinder, which made it intolerable for me (having all manual focus lenses in particular; and since one can't relay on the ability of autofocus to work in all situations, I would find it intolerable even if I had autofocus lenses).

Just my $ 0.02  ;D
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24x36

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Re: What chance has Sigma's SD1?
« Reply #119 on: May 31, 2011, 10:37:47 pm »

Interesting how people throw around numbers without actually looking at test data.  If lenses were really diffraction limited at such apertures, then resolution would not improve with increasing pixel density.  Instead, if on looks at Photozone tests done with 8MP and with 15MP (Canon, Bayer pattern) sensors, one sees a substantial increase in resolution even at f22:

8MP:


15MP:



There is a difference between the point beyond which "diffraction blurs the image more as the aperture shrinks" and the point beyond which "diffraction prevents any further increase in resolution by increasing the pixel density".  The Photozone data shows this quite concretely.  Yes, diffraction decreases the resolution beyond about f8, and yes, increasing pixel density increases resolution even in the regime well beyond f8.

The physics here is that MTF decreases linearly with aperture, but it is not zero at Nyquist for either sensor, and therefore there is a benefit to finer pixel pitch.

The trouble is, this "comparison" requires making quite the assumption - that is, that the only difference between the two sensors is pixel count. In fact, we're talking about sensors two generations apart. Differences in sensor technology, demosaicing algorithms, and so forth may have more to do with any increase in resolution than pixel count does, for all we know. Unless we can compare two sensors from the same generation in the same format using the same technology from the same manufacturer with different pixel counts, we're comparing apples and oranges. We also don't have the "lines" related in any way to what the maximum resolution as limited by diffraction might be (both cameras may be below it, for example, which means you could see no limitation in these "tests," even though it would apply if the cameras performed well enough for the limitations to be seen). Quite frankly in the digital age I'm not so confident that "lines" are actually being resolved, as opposed to being interpolated, so I'm not especially convinced by such "data." I'm skeptical of something so easy for square pixels to artificially replicate through algorithm guesswork (i.e., straight lines) as being a meaningful subject of comparison - a more challenging, non-linear subject is more likely to be a realistic test of real-world resolving power.
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