Hi All,
well, ISO 50 (former 18 DIN) means, that the foveon image sensor becomes exposed to twice the amount of light compared to ISO 100 four times as much compared to ISO 200, eight times as much compared to ISO 400 and so forth.
The Foveon sensor architecture unfortunately has disadvantages in noise performance compared to the most modern Bayer-designs.
Each photo-cell produces some electric disturbing signal ... i.e. it produces some small voltage even if there is no light triggering this signal (like the little sonic noise which you might notice with a microphone or an amplifier.)
With an image sensor, these disturbing signals are called "dark currents".
http://electronicdesign.com/Articles/ArticleID/14702/14702.html
The Foveon X3-(three layer) sensor supposedly is the most accurate image sensor on the market because each pixel is scanned by three separate photo cells, recording the ground colours each separately and independently.
The problem now is, that you accumulate the dark current of three photo cells per pixel. The other point is, that the light has to "dive" through the silicon layers and becomes dimmed this way a bit, which reduces the signal to noise distance further.
Honestly said, the Foveon cannot really compete with Bayer's high ISO performance. Up to ISO 400 it can keep up with Bayer .... ISO 800 still is acceptable ... ISO 1600 can be managed with some software tricks ... I did a thread on the issue.
Although picture noise is no real problem up to ISO 400, you should never use sensor sensivities higher than necessary, to cut down noise to a minimum.
At ISO 50 the signal to noise ratio is as good as possible. Picture noise comes down to an absolute minimum ... although the difference to ISO 100 hardly is visible.
So ISO 50 is a good idea when very big poster prints are planned and noise must be reduced to the lowest possible extend ..... but .....
I do not recommend ISO 50 if the scene contains very bright shiny elements or very bright reflexions. Then you risc to really overexpose the Foveon!
Iso 50 means that the sensor loses its typical capacity of tracing details in the lights.
Simply put .... noise is best at ISO 50 but "dynamic" is best at ISO 200 or ISO 400.
So I often do a compromise, using ISO 100, which is my standard setting.
See you with nice pictures
Klaus
well, ISO 50 (former 18 DIN) means, that the foveon image sensor becomes exposed to twice the amount of light compared to ISO 100 four times as much compared to ISO 200, eight times as much compared to ISO 400 and so forth.
The Foveon sensor architecture unfortunately has disadvantages in noise performance compared to the most modern Bayer-designs.
Each photo-cell produces some electric disturbing signal ... i.e. it produces some small voltage even if there is no light triggering this signal (like the little sonic noise which you might notice with a microphone or an amplifier.)
With an image sensor, these disturbing signals are called "dark currents".
http://electronicdesign.com/Articles/ArticleID/14702/14702.html
The Foveon X3-(three layer) sensor supposedly is the most accurate image sensor on the market because each pixel is scanned by three separate photo cells, recording the ground colours each separately and independently.
The problem now is, that you accumulate the dark current of three photo cells per pixel. The other point is, that the light has to "dive" through the silicon layers and becomes dimmed this way a bit, which reduces the signal to noise distance further.
Honestly said, the Foveon cannot really compete with Bayer's high ISO performance. Up to ISO 400 it can keep up with Bayer .... ISO 800 still is acceptable ... ISO 1600 can be managed with some software tricks ... I did a thread on the issue.
Although picture noise is no real problem up to ISO 400, you should never use sensor sensivities higher than necessary, to cut down noise to a minimum.
At ISO 50 the signal to noise ratio is as good as possible. Picture noise comes down to an absolute minimum ... although the difference to ISO 100 hardly is visible.
So ISO 50 is a good idea when very big poster prints are planned and noise must be reduced to the lowest possible extend ..... but .....
I do not recommend ISO 50 if the scene contains very bright shiny elements or very bright reflexions. Then you risc to really overexpose the Foveon!
Iso 50 means that the sensor loses its typical capacity of tracing details in the lights.
Simply put .... noise is best at ISO 50 but "dynamic" is best at ISO 200 or ISO 400.
So I often do a compromise, using ISO 100, which is my standard setting.
See you with nice pictures
Klaus
