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Sigma lost it completely.
#21
[quote name='Brightcolours' timestamp='1305944913' post='8711']

That could only happen if the CFA actually would just let through one wavelength, which is doesn't. Each "colour" lets through a wider band of the spectrum, making your example more or less purely theoretical...

[/quote]

Brightcolours, you've got some good information, and I for example appreciate you reminding us of the aspects of moire suppression problems that are not solved by a full-color-at-each-photosite sensor such as the Foveon.



But now you appear to be reaching for negatives about obvious good arguments for the Foveon sensor. As if you want to protect a preconceived idea that the Foveon sensor can't have any resolution advantage over a Bayer color filter array sensor. You seem here to have trouble acknowledging individually good aspects of an overall counter-argument...a basic tenet of effective rhetoric, to support the impression that your first priority is the facts. Of course we can all agree further that the highest and best use of a public forum is a search for truth with our peers, not to win arguments.



I happen to be both a professional photographer (albeit not a great one) and software developer. And have written a freeware raw file processor (i.e. a piece of software, albeit not a brilliant one). With a journeyman, but not ultra simplistic, demosaicer algorithm of course. But one need not be a computer scientist to realize that, when half the Bayer pixels are covered by a green filter, a quarter of pixels by a red filter, and a quarter covered by a blue filter, that in real green areas of an image (think foliage) a 14 megapixel sensor performs pretty much like a 7 megapixel sensor, resolution-wise. And in this example, in real red (think indoor lighting tending to this) or blue areas (think open shade's tendency) the sensor resolution begins degrading on the way down to 3.5 megapixels, resolution-wise. Similarly, in real yellow or cyan ("minus blue" or "minus red") areas you're heading down to 10.5 megapixels, and as the areas get more magenta ("minus green") you're heading South down to 7 megapixels. And man the perceived noise of every type goes up in real red, blue, or magenta areas when you don't have access to much data from the sweetest (most important to human eyes for luminance), green pixels.



Yeah none of the Bayer filters are perfect, and most colors and light sources in the world are not monochromatic, but I assume that a demanding user like yourself would be interested in even a 25% change in performance. And it's sure easy to imagine a scene or subject with say 75% of the green light gone that you'd see in a picture of a white thing in daylight.



Now at a higher and non-scientific level, it's true that modern cameras have such high resolutions that a typical 4x6 or 8x10 inch enlargement probably has little need of more than half or even a quarter of its nominal pixels to produce a nice image. And yes, the green filters over the various sensor sites aren't absolutely perfectly only letting in green light, etc. And it's true that any individual photo is not likely to have huge areas of pure magenta, or pure red, or pure blue, that knocks out the greens. And it's true that in a given year, there is no guarantee that the Foveon pixels are lower noise than competitor's Bayer array pixels.



But it would be easier for a camel to pass through the eye of a needle than for Bayer filter arrays to deliver full resolution in strongly colored areas. (Indeed in some of the very finest photos, the area of most visual interest is often the area of strongest coloration or are in the weirdest of light.) And Bayer array noise performance degrades in any area lit by light that especially is red, blue or magenta in cast (see above).



Yes, a given Bayer sensor could be so much more sensitive and noise-free than a Foveon in every way, that even with 1.5 hands tied behind its back, that Bayer sensor could whup the tar out of a Foveon with the same nominal resolution. Nah, not in strongly magenta, red or blue image areas, or in strongly bluish, reddish or magenta-ish light.



For every quibble you could make about the non-green light that makes it past the green filters, etc, there are a ton more arguments to make that a (say Foveon) camera with merely 50% less noise in strongly color-cast lighting conditions, or when photographing strongly colored scenes, would work at noticeably higher ISO with the same quality as a Bayer array camera. Because the resolution (to the extent that resolution is not degraded by noise which might be bad in say a poor-quality Foveon sensor) of a Foveon sensor never changes with strongly colored lights or subjects, and a Bayer sensor's resolution always changes in such cases.



Nobody's saying a Foveon camera has exactly 3 times the resolution of the same-geometery Bayer array camera. And nobody's saying that you ever take pictures in conditions or of subjects where the marginal advantages of Foveon sensors are significant. But neither will I let pass without protest your repeated implication that a Foveon camera has no better potential for resolution and noise in scenes that are either colored, or lit with colored (for example far from 6500K) light. Which is a whole lot of scenes.



Within the scope of this reasoning is still room for a given Bayer sensor to often and everywhere perform in a way that is not noticeably worse than a Foveon sensor. But by that logic one would have to also observe that an 8 megapixel camera can often and everywhere provide all the resolution that many a well-heeled user might notice or need. Similarly if you were a not-interested-in-max-quality user, I would agree that you might never notice the unique benefits of a Foveon sensor compared to a Bayer. But you seem to be just the kind of user who'd appreciate and acknowledge the relative, all other things being equal, greater resolution consistency and thus more consistently-smoother-looking images from a Foveon sensor camera of a given pixel pitch.
#22
[quote name='Brightcolours' timestamp='1305944913' post='8711']

That could only happen if the CFA actually would just let through one wavelength, which is doesn't. Each "colour" lets through a wider band of the spectrum, making your example more or less purely theoretical...

[/quote]

If you say so.



Let’s do a very simple experiment. Open Word or some equivalent program. Fill page with some random text, black preferably. Take a picture of the screen. Then make the background of the text pure red (as in FF0000) and take another picture. And then examine both pictures at 100% view. Unless you monitor is miscalibrated pretty badly, the difference should be pretty obvious <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/rolleyes.gif' class='bbc_emoticon' alt='Rolleyes' />
#23
[quote name='popo' timestamp='1305967448' post='8713']

Since this is *still* being bought up, again I reiterate I acknowledge that *some* luminance information can be gathered by the others, but their value is significantly lower in that role.



Also, for fun let's read the original Bayer pattern "Color imaging array" Patent. At least I would in more detail if I wasn't leaving for a shoot in a moment.

[/quote]

Also, for fun notice the difference in detail different RAW converters get.



I can't make it different, the AA-filter is pixel pitch based, not Bayer pattern based, and the green, red and blue all have pretty much equal amounts of luminance information (Bayer CFA gives in the order of 6.4% less luminance information, this is NOT detectable with our eyes looking at images). It is upto the RAW converter method juts how much information gets extracted.



The big difference in looks of a Foveon/Sigma camera and a Bayer CFA camera with AA-filter, is just the AA-filter.



AA-filterless Bayer CFA sensors start o show the same "detail", the same aliasing stair stepping PER PIXEL.That is why some people prefer having the AA-filter removed.



Personally, I do not care too much for the oversharpened look of AA-filterless images.

Anyway, the Leica M9 is the easiest camera to look for Bayer CFA AA-filterless images for,



I know that the original patent filers called the green sensels "luminance sensitive" and the red and blue ones "chrominance sensitive", but that is jut how those inventors looked at it.



CFA demosaicing has made HUGE strides since then, and with it the view of how much luminance detail can be extracted from every colour channel.



This is true for both AA-filterless and AA-filtered sensors.
#24
[quote name='Lomskij' timestamp='1305970073' post='8715']

If you say so.



Let’s do a very simple experiment. Open Word or some equivalent program. Fill page with some random text, black preferably. Take a picture of the screen. Then make the background of the text pure red (as in FF0000) and take another picture. And then examine both pictures at 100% view. Unless you monitor is miscalibrated pretty badly, the difference should be pretty obvious <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/rolleyes.gif' class='bbc_emoticon' alt='Rolleyes' />

[/quote]

So... did you do the experiment? And did you use a good convertor? (Like RPP for instance)? And would you like to share the results then?



Personally I never encounter flat 100% red screens with black text worthy of photographing, so no matter which outcome, it remains pretty meaningless <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='Wink' />
#25
[quote name='Brightcolours' timestamp='1305971973' post='8719']

So... did you do the experiment? And did you use a good convertor? (Like RPP for instance)? And would you like to share the results then?



Personally I never encounter flat 100% red screens with black text worthy of photographing, so no matter which outcome, it remains pretty meaningless <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='Wink' />

[/quote]

Sure, here you go.



The reference shot:



[Image: sample1.jpg]



And the red one:



[Image: sample2.jpg]



I’ve used Adobe Camera Raw 6.3, but you’re more than welcome to do your own test with a different camera and different raw converter. Just out of interest (though I don’t understand what you find wrong with a calibrated PVA monitor) I’ll print a few sheets with a colour laser printer on Monday and redo the test <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='Wink' />
#26
[quote name='Lomskij' timestamp='1305973041' post='8720']

Sure, here you go.



The reference shot:



[Image: sample1.jpg]



And the red one:



[Image: sample2.jpg]



I’ve used Adobe Camera Raw 6.3, but you’re more than welcome to do your own test with a different camera and different raw converter. Just out of interest (though I don’t understand what you find wrong with a calibrated PVA monitor) I’ll print a few sheets with a colour laser printer on Monday and redo the test <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='Wink' />

[/quote]

Great, so what we get is the realization that the screen photographed at such magnification levels is very unsharp (what kind of screen is that???An old crappy CFT?) and that to "test"w aht you say you are testing, you need to use a darker grey with black letters to compare in the first place, because through contrast differences we are unable to compare.



Besides that, with your "test" you really only are testing our visual system, not detail in the red channel.. for that, you will need to actually transfer the detail information to a spectrum our eyes can handle in the same way.



Not a test which shows anything, I am afraid.
#27
[quote name='Brightcolours' timestamp='1305977054' post='8722']

Great, so what we get is the realization that the screen photographed at such magnification levels is very unsharp (what kind of screen is that???An old crappy CFT?) and that to "test"w aht you say you are testing, you need to use a darker grey with black letters to compare in the first place, because through contrast differences we are unable to compare.[/quote]

I know that you’re trying to be funny, but unfortunately this point is invalid – we’re not comparing two monitors, we’re comparing two images on the same monitor, and the first one is sharper than the second one. And also like I said, I’ll do a test with printed sheets in a few days.



[quote name='Brightcolours' timestamp='1305977054' post='8722']Besides that, with your "test" you really only are testing our visual system, not detail in the red channel.. for that, you will need to actually transfer the detail information to a spectrum our eyes can handle in the same way.[/quote]

Nope, it tests exactly the detail in red channel – and we’re using our visual system to see the difference. Because it’s the way the photography works – pictures are meant for our eyes, not something else. And it’s for human eyes to determine whether pictures are sharp or not.



[quote name='Brightcolours' timestamp='1305977054' post='8722']Not a test which shows anything, I am afraid.

[/quote]

So basically all your arguments are “I don’t like it so it has to be wrong”? The thing is that it takes just five minutes to do it by yourself and either confirm my point or prove me completely wrong. Why don’t you do it?
#28
[quote name='Lomskij' timestamp='1305978433' post='8724']

I know that you’re trying to be funny, but unfortunately this point is invalid – we’re not comparing two monitors, we’re comparing two images on the same monitor, and the first one is sharper than the second one. And also like I said, I’ll do a test with printed sheets in a few days.





Nope, it tests exactly the detail in red channel – and we’re using our visual system to see the difference. Because it’s the way the photography works – pictures are meant for our eyes, not something else. And it’s for human eyes to determine whether pictures are sharp or not.





So basically all your arguments are “I don’t like it so it has to be wrong”? The thing is that it takes just five minutes to do it by yourself and either confirm my point or prove me completely wrong. Why don’t you do it?

[/quote]

No, what you are writing is nonsense.



EITHER you test out\r visual system (how we perceive red (66% less bright, by the way) compared to white,



OR you test the actual information being captured of a red subject by Bayer CFA sensors.



You did do neither, but mostly the test was of the 1st type, nothing about the 2nd type.



Why I don't do it is because it is bullshit, what you say you are testing. It is a nonsense test which does not hold up in any way.

So, device a better test to actually test the detail recovery of a red/blue/green subject, and a good way to actually evaluate the detail (so, without our eyes being the ones tested).
#29
Guys please calm down.

There are hundreds of threads over at DP about the foveon sensor and its benefits - all talked to death. I use both bayer and foveon and I keep the foveon because I like the photos I can take with it in certain situations, but it is by no means a perfect system. Both sensor types have there own right to exist in my bag.



I found this to comparisons very helpfull to understand why a foveon looks differnet to my eyes.

http://www.dpreview.com/reviews/sigmadp1/page20.asp

http://www.ddisoftware.com/sd14-5d/



Oh and Klaus are you going to review some lenses on the SD-1? - (you might have to cut down on your holidays for a while) <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='Wink' />
#30
Nuts.
  


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