Originally posted by Pentaxor just one question, do you have the SD1 on hand that draw such conclusion?
No. Nor do I need one as I do have basic understanding on sensor technology and the laws of physics. They are all that are needed.
Originally posted by Pentaxor from my understanding, you based this on the assumption that the Foveon Sensor used on the SD1 is the same Foveon Sensor used on it's smaller MP predecessors.
You have misunderstood. I am basing my estimates on how silicon and light interact, how demosaicing works (for Bayer), how sensors work. I've not mentioned the old sensor at all, and if I recall right, I mentioned the quite recent Sigma patent describing another sensor, with 15/3.8/3.8 Mp layers.
I am puzzled on how you could come to the idea that I somehow have guessed what the SD1 sensor if from the performance of some other sensors.
Originally posted by Pentaxor this is based on your assumption that Sigma didn't or hasn't made any improvements on the their past sensor design due to lack of advertised or publicly shown patent. I think Pentax did the same thing as well. honestly, I would had
First, I did mention certain patent (either in reply to you or to another person) whch describes an improved sensor. The biggest single improvement is the use of (a modified) 4T design which allows for correlated double sampling to take care of one of the two biggest sources of Foveon noise, the reset noise. This should lower the read noise from what it is now (it's somewhere between 30 and 60e-, can't remember for sure) to somewhere between 5 and 10e- (or a bit more or less) at the base ISO. This is a massive improvement. The other main source of noise with Foveon is unfortunately not fixable with a three-layer silicon design - it is the color separation problem. Due to the probabilistic nature of photon absorbion in medium, the system which relies on photon penetration depth for color separation is by nature of very weakly signal separating. This leads to massive noise for color imagery.
Originally posted by Pentaxor agreed with you if and only if this was the same previous Foveon sensor design that is only increased with MP count. besides, it wouldn't make any sense that Sigma would increase sensitivity by 2 stops if they already had some problems with regards to noise with their previous cameras which I'm not refuting.
Well, their pricing makes no sense either, lots of other stuff in the world also make no sense.
Anyhow, you evidently quoted the ISO 6400 specification compared to ISO 1600 or the earlier Sigma cameras. You should make a note that this is a
camera specification,
not sensor. Assuming that there is a variable signal apmlifier in the sensor, it is likely to be able to boost the signal at most to ISO 1600 (this is pretty much standard for all the sensors as it makes little sense going beyond - ideally of course there would be no need for VGA, and that day is getting closer) and the higher ISOs are just software post processing. For example the sensor inside the Pentax K-5 has a maximum ISO of 1600 as well. The rest is just camera pushing in software.
Originally posted by Pentaxor I'm saying this if the SD1's Foveon sensor is the same sensor on the SD14/15,
The sensor has different dimensions, different pixel pitch, different resolution - how on earth it could be the same sensor?
Originally posted by Pentaxor Sigma is making a big and stupid mistake to increase an already poor High ISO performance. and even yet more stupid thing if such camera is priced at $9k with a performance of an improved SD15 with the very same sensor.
The ISO numbers of the camera are absolutely irrelevant for this topic, nor do they have anything to do with the noise performance of the sensor compared it's predecessor. It would have made sensor for the Sigma marketing department t demand ISO 100.000 just to make the camera specs look better...
Originally posted by Pentaxor Luminous Landscape said it best that it is wise to wait and see if such camera does indeed live up to the hype and worth the price. besides, I think it's better to be optimistic rather than not. who knows, they hit a goldmine rather than an old relic.
LL is one of the worst sources for technology information in the internet. And yes, before you ask, even I am a better source
There is no reason to be optimistic or pessimistic. Enough facts are known - about sensor technology in general, about the Foveon sensor technology principles, about how resolution is measured and how our eys see it, about how our eyes see color compared to how the color is created by different technologies, incluging the silicon separation of Foveon, of photon behavior and so on. There is no magic, nor many parameters we don't know.
This new sensor will have quite a bit better signa/noise ratio than it's predecessor, especially for black and white photography, it'll also have quite a bit more resolution than it's predecessor, though far less than Sigma fans and marketing would want us to know. Borrowing your terminology - it won't be a goldmine, nor a relic, just a logical evolution of the previous generation.
Anyhow, at that price point it won't sell at all. It simply is a weak product for professionals of pretty much any field, apart from someone shooting landscapes and travelling light. It won't be good for sports and such for obvious reason, it hardly is the most sensible tool for photo journalism at that price, and typically what is shot with medium format requires accurate colors (for human color vision), something that is impossible to to achieve with the Foveon tehnology (it is not someting that can be fixed in that techonology) and also MF has far higher resolution, far better tonality and so on.
Still, if/when the price comes down to under 1k, I might buy one as it is an interesting product, though probably not as by that time the world has moved on.