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Sigma/Foveon Questions
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Sigma/Foveon Questions
Ray Fischer wrote:
Bubba wrote: I don't understand how a sensor can claim 14 pixels, and the photo itself be 4. That's easy - Sigma lies. They pretend that you can take a single pixel and split it up into three colors and have that be three pixels. They don't lie. It's a different kind of sensor with sufficiently different kinds of pixels and properties that the sensor megapixel numbers aren't comparable with hose of Bayer sensors. It's like trying to compare the engine capacities of ordinary car engines with cylindrical pistons and rotary Wankel engines. The numbers have to be normalised before you can make comparisons. Of course it may well be the case that Foveon exaggerate a bit in normalising their numbers. But then the megapixel numbers of Bayer sensors are exaggerated themselves. An ordinary 14MP Bayer sensor desn't give you the image resolution you'd expect from 14MP. Some gets lost in the necessary AA filter. And that's not a constant, because it's a trade off between detail resolution and aliasing artefacts. Some makers give you more detail, in effect more megapixels of detail, at the cost of more aliasing artefacts in the situations where aliasing obtrudes. So there's no simple way of normalising Foven megapixel numbers to make them comparable to Bayer megapixel numbers. You simply have to look at the results and make a subjective appraisal of comparability. Just as you have to do when comparing Bayer megapixels from cameras with different attitudes towards aliasing, such as Leica, Nikon, and Hasselblad. -- Chris Malcolm |
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Sigma/Foveon Questions
In article , Chris Malcolm
wrote: I don't understand how a sensor can claim 14 pixels, and the photo itself be 4. That's easy - Sigma lies. They pretend that you can take a single pixel and split it up into three colors and have that be three pixels. They don't lie. yes they do. calling it anything other than 4.6 or 4.7 megapixels is a lie (it's actually 4.65, so either one is fine). It's a different kind of sensor with sufficiently different kinds of pixels and properties that the sensor megapixel numbers aren't comparable with hose of Bayer sensors. the difference is that bayer has one layer and foveon has three layers per pixel. you don't get to count each layer as a separate pixel. if you had a single pixel sensor with 1 million layers, would that be a megapixel sensor? no. It's like trying to compare the engine capacities of ordinary car engines with cylindrical pistons and rotary Wankel engines. you can measure horsepower, torque and engine displacement for both. The numbers have to be normalised before you can make comparisons. pixel is normalized. Of course it may well be the case that Foveon exaggerate a bit in normalising their numbers. exaggerate a bit? they multiply it by 3. that's a lot. But then the megapixel numbers of Bayer sensors are exaggerated themselves. no they're not. An ordinary 14MP Bayer sensor desn't give you the image resolution you'd expect from 14MP. it does for me. Some gets lost in the necessary AA filter. And that's not a constant, because it's a trade off between detail resolution and aliasing artefacts. Some makers give you more detail, in effect more megapixels of detail, at the cost of more aliasing artefacts in the situations where aliasing obtrudes. it doesn't matter how much detail there is in a photo, the number of pixels on the sensor does not change. So there's no simple way of normalising Foven megapixel numbers to make them comparable to Bayer megapixel numbers. yes there is. You simply have to look at the results and make a subjective appraisal of comparability. Just as you have to do when comparing Bayer megapixels from cameras with different attitudes towards aliasing, such as Leica, Nikon, and Hasselblad. sure, but the subjective quality doesn't change the number of pixels on the sensor. |
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Sigma/Foveon Questions
In article
, Bubba wrote: At the risk of getting a rain of more invective on a day that's rainy enough in my parts, does this mean that you can't...focus?! focus and zoom are separate things. assuming you are talking about the dp1/dp2 series, they can focus (slowly), but there is no zoom. there is auto-focus, but as i said, it's slow. If you can focus, there has to be *some* zoom (or is it just digital)? there is no optical zoom. it's a fixed single focal length lens. the dp1 has a 28mm equivalent lens and the dp2 has a 41mm equivalent. if you want a focal length other than either of those, you're need a different camera. sigma's strategy is to have you buy multiple cameras for every focal length you want. however, there is digital zoom and the sigma fanbois even claim that the sensor is *so* good that digital zoom is just as good as optical zoom (they really do say that). These Sigma owners, and the gentleman on another thread who recommended a camera with a Foveon sensor to me, seem to use it for what I want it for: nature photography in low light, foveon is one of the worst choices for low light. it's noisy to begin with but it gets really bad beyond iso 200. without the artifacts that I suppose you all here are calling "aliasing." (I've called it red flare, because that's what I was told it was by the British folk on my Serif editing software sight--a nicer bunch of people, I have not met on any forum--including those on which I've tangled with nospam.) red flare is not aliasing, however, the dp1/dp2 series have a red dot problem, although the latest versions have minimized it. |
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Sigma/Foveon Questions
Chris Malcolm wrote:
Ray Fischer wrote: Bubba wrote: I don't understand how a sensor can claim 14 pixels, and the photo itself be 4. That's easy - Sigma lies. They pretend that you can take a single pixel and split it up into three colors and have that be three pixels. They don't lie. It's a different kind of sensor with sufficiently different kinds of pixels and properties that the sensor megapixel They lie. When you measure the size of the image it produces you see that it is 4.6 mega pixels. That is the cold, hard fact. No amount of sophisty, lies, or self-serving bull**** will alter that fact. -- Ray Fischer |
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Sigma/Foveon Questions
In article
, Bubba wrote: red flare is not aliasing, however, the dp1/dp2 series have a red dot problem, although the latest versions have minimized it. If you're not yanking my chain and are serious when you use the term "red flare"--which no one on the threads I've started has even acknowledged exists-- this is the problem to which i refer: http://www.testiweb.com/images/jpg/d...20dp1/Jpg%2095 0x%20or%20lower/foveon_flares_2_SDIM0025_950x.jpg http://www.testiweb.com/images/jpg/d...20dp1/Jpg%2095 0x%20or%20lower/foveon_flares_3_SDIM0043_950x.jpg http://raist3d.typepad.com/files/sigmanotoksunclouds.jpg In a $500-$600 range, is a camera available that will lessen or do away with red flare without the purchase of additional lenses or filters? plenty of them. So if these wacky Sigma cameras have no zoom except digital, but if their partisans swear by the cameras' sensors' ability to get rid of/ diminish this flare, that makes me ask Why would these people not want another P&S camera that *has* optical zoom (or at least the ability to attach a lens) AND a CMOS sensor. they're delusional. |
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Sigma/Foveon Questions
In article
, Bubba wrote: Only the last link works, but I see what you mean. It looks like there are red polka dots in the sun's rays. try copy/pasting it if it wrapped, or just use these: http://tinyurl.com/y5zam25 http://tinyurl.com/y46nhpj In a $500-$600 range, is a camera available that will lessen or do away with red flare without the purchase of additional lenses or filters? plenty of them. I am familiar only with Canon products and do not understand this Third-Fourths or Fourth-Third thing (if the term refers to CMOS sensors). Canon offered me a "steady-date" discount on new equipment, and I want to get a SX S1. 4/3rds is a smaller sensor than what's in nikon and canon slr cameras, with a 2x crop factor versus 1.5 and 1.6. the slrs based around the 4/3rds sensor weren't that much smaller than the smallest nikon or canon slrs and never sold that well, but olympus and panasonic have done away with the mirror box and now have what they call micro-4/3rds, which is basically a large sensor compact camera. So if these wacky Sigma cameras have no zoom except digital, but if their partisans swear by the cameras' sensors' ability to get rid of/ diminish this flare, that makes me ask Why would these people not want another P&S camera that *has* optical zoom (or at least the ability to attach a lens) AND a CMOS sensor. they're delusional. Is that it? what else could it be, when someone buys a sub-5 megapixel camera that has noise and other problems and claims it is as good or better than an 18-24 megapixel camera? it's one thing to like a certain look but it's another to claim things that are simply not possible. |
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Sigma/Foveon Questions
Ray Fischer wrote:
Chris Malcolm wrote: Ray Fischer wrote: Bubba wrote: I don't understand how a sensor can claim 14 pixels, and the photo itself be 4. That's easy - Sigma lies. They pretend that you can take a single pixel and split it up into three colors and have that be three pixels. They don't lie. It's a different kind of sensor with sufficiently different kinds of pixels and properties that the sensor megapixel They lie. When you measure the size of the image it produces you see that it is 4.6 mega pixels. That is the cold, hard fact. No amount of sophisty, lies, or self-serving bull**** will alter that fact. Of course it doesn't. But I was talking about the image implications of that fact. People are using image MP as a measure of image quality. Different kinds of image sensor technology buy you different amounts of image quality for the same number of pixels. If you look at the two different methods that have to be used in order to translate from sensor pixels to image pixels from the two kinds of sensor technology you'll see there is an inherent difference in luminance resolution, and a larger difference in chrominance resolution. -- Chris Malcolm |
#9
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Sigma/Foveon Questions
In article , Chris Malcolm
wrote: That's easy - Sigma lies. They pretend that you can take a single pixel and split it up into three colors and have that be three pixels. They don't lie. It's a different kind of sensor with sufficiently different kinds of pixels and properties that the sensor megapixel They lie. When you measure the size of the image it produces you see that it is 4.6 mega pixels. That is the cold, hard fact. No amount of sophisty, lies, or self-serving bull**** will alter that fact. Of course it doesn't. so you agree they lie. But I was talking about the image implications of that fact. People are using image MP as a measure of image quality. it's a major factor but it's not the only one. Different kinds of image sensor technology buy you different amounts of image quality for the same number of pixels. If you look at the two different methods that have to be used in order to translate from sensor pixels to image pixels from the two kinds of sensor technology you'll see there is an inherent difference in luminance resolution, and a larger difference in chrominance resolution. the luminance resolution is about the same as another 4.6 megapixel sensor (alias artifacts is not resolution, it's false detail) and the eye can't see the extra chroma resolution. however, the point is that the number of pixels is still 4.6 million, no matter what kind of image the sensor produces. |
#10
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Sigma/Foveon Questions
Chris Malcolm wrote:
Ray Fischer wrote: Chris Malcolm wrote: Ray Fischer wrote: Bubba wrote: I don't understand how a sensor can claim 14 pixels, and the photo itself be 4. That's easy - Sigma lies. They pretend that you can take a single pixel and split it up into three colors and have that be three pixels. They don't lie. It's a different kind of sensor with sufficiently different kinds of pixels and properties that the sensor megapixel They lie. When you measure the size of the image it produces you see that it is 4.6 mega pixels. That is the cold, hard fact. No amount of sophisty, lies, or self-serving bull**** will alter that fact. Of course it doesn't. But I was talking about the image implications of that fact. There aren't any. Sigma lies. People are using image MP as a measure of image quality. People do all manner of stupid things. That doesn't justify lying. -- Ray Fischer |
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