I don't agree with that. If a pixel needs X photons to produce response higher than noise then bigger pixel will catch them faster than smaller. Getting smaller and smaller pixels increases needed exposure time. Bigger pixel is almost like binning, just "permanent".
you don't need the signal to be larger than the noise, as long as the noise is random, if you have enough samples, you can pull the signal out
but the smaller pixel sensors are also achieving very low read noise
exactly, you can bin small pixels to become large pixels
Historically you can look at some SBIG ST-9 exposure times - a camera with 20x20 pixels. Resolution is much lower but also exposures times are also lower than when compared against similar camera with smaller pixels.
again it depends on sensitivity and full well.
Purdyd wrote:
the IMX174MM is much more sensitive than the ICX285, has lower read noise, higher dynamic range, hiher resolution, and huge advantage in fps
http://www.dangl.at/ausruest/atik_314/atik_314_e.htm
Atik314L+ has around 4e read noise, and extremely low dark current.
i suspect that is the cooled spec if you look at the pt grey specs of an uncooled camera, it is higher
Depending on QE chart IMX174 has 5-15% higher QE than ICX285 in visible light. In H-alpha those sensors are pretty much even. Actual dynamic range of cooled ASI174 will depend on the total noise the sensor + electronics will give but IMHO I doubt it will exceed 12-14bit range in which ICX285 operates. Point Grey states 30Ke saturation capacity and 7e temporal dark noise (for one of their cameras). So to get noticeably better dynamic range the read noise would have to be as low as in Atik (but against 2x well size).
your comparing cooled versus uncooled - if you look at the pt grey comparison charts which is more even comparison since as you note electronics is an issue, and the data sheets, the IMX174 is better
As for speed - IMX174 can run faster, and that's an advantage for Solar System imaging. For DS imaging everything is optimized for low noise readout so a very good dual purpose camera would have electronics and software optimized for fast framerate and also optimized for slow low noise framerate - which isn't that easy. ICX285 in DS cameras does frames around ~1FPS while lab cameras do around 15-20 FPS but with higher shot noise.
generally that means a slower A2D conversion and slowing it down is pretty easy, speeding up is harder
sony also provides different bit ranges for the A2D which affect conversion speed
so if it can do fast it could certainly do slow
now the question is well chip makers implement that capability
and that is always the problem with astrophotgraphy, it is such a small niche market
.
I think I am a little leery about comparing a beta camera with a production camera
and yes, I really look forward to seeing some comparisons of the cooled modern CMOS sensors with the more established CCD's
