I think you are right as far as CCD type tech goes.

but the sensor could be reset and keep on counting from 1 and add that to the total, like the next frame in a vidcam, or a sort of automatic HDR, or it could use a completely different sensing technology.

i think not. my understanding is that photons have no mass at rest, since anything with at rest mass must have infinite mass at light speed and thus photons mass at lightspeed (which is the only speed you ever see them at!) is zero x infinity which is indeterminate. in fact i guess their mass at speed should be calculable from their energy but i don't know. certainly energy varies with frequency just like any other wave. (even though they are not really a wave)

I think it is possible to determine precisely the details of a quantum particle's state in the past, if you don't mind precluding knowledge of where it went next. is that right?

we don't care what happens to the photon after it hits the sensor, so i suspect that allows us to determine both its energy and its position when it does hit the sensor.

also we don't actually need to know its position very precisely, even the mini photosites on that new chip are 5-10 wavelengths across.

this is getting a bit speculative though.

I'd really like to know if the variable gain amplifier ISO stage can be dispensed with when using high bit depth A/D and existing sensors, and why it hasnt been done already, which is a question a pentax engineer could certainly answer if they wanted to...

of course its likely that i am misunderstanding something about how current cameras work...

I'd also like to know what the obstacles to an inherently noise free 'photon counter' type sensor are, where the only "noise" is not technology noise but random fluctuations in the photon stream, plus photon quantisation issues. this is fascinating because its one of the ways in which the real world is actually digital rather than analog and we could concievably capture it bit for bit.

exactly, but the resolution of the full 22bits is greater than the resolution of the sensor. so why do we need to change the pre ADC amplifier gain with the ISO setting?

if the full 22bit data were scanned for peaks before/during resampling down to 12bit, then we'd effectively have after the fact automatic iso and never have a clipped image unless the CCD was saturated (ie never clipped in light levels that we'd normally use faster iso speeds for.)

individual photons have an energy, which corresponds to wavelength i think.

certainly its difficult to observe wavelike behaviour in a single quanta, but I think the concept of a wavelength of an individual photon has some validity.

if not then colour and wavelength must be built up through interaction between quanta. I'll look it up if i can find out what exactly to look up!

I'm not a physicist though...

a quick google found this:

http://focus.aps.org/story/v3/st21

which tends to support my understanding about it, even though its actually about soemthing more esoteric again

EDIT & addition: the famous two slit experiment, in which photons fired individually display interference effects (ie the single photon "interferes with itself" [!!]) would seem to indicate that single photons have wave like properties.

however i'm sure there would be quantum effects in a photon counting sensor as I was advocating, and it would be great if someone who knows could comment on what they might be.

OK so I'm talking to myself here, but i realised that they are claiming smaller pixel size as well as higher sensitivity, so I guess it will apply to hi res sensors in due course.

I had to look up to be sure what a spectrophotometer was , but i see that (as I thought from the name) it measures actual wavelength rather than just human perceived colour.

is that the bit of what I said (about recording the wavelength of each photon) that you were thinking about?

what is your work?

although, i guess, that to do images of typical current dynamic range ie 8bit, you could get away with only 256 photons per pixel per channel if you could count them accurately. or 768 photons per pixel total for full colour.

that certainly is low light, and i would assume that this new device is getting closer to that theoretical limitation, so it could be good!

the one they are selling is only 640x480 pixels I note!

I can't interpret the tech specs given here into bit depth dynamic range or number of photons required to make a difference in the output, can anyone else?

http://www.planet82.com/english/product/smpd_02.asp

they claim 120dB dynamic range, thats well in excess of 16bit and implies a very high photon per pixel saturation point at least compared with the 80,000 photons I've seen quoted as normal.

I'd like to see some actual real info on what it does different.

theres a fundamental limitation in terms of the number of photons hitting each pixel, and higher pixel counts and thus smaller pixels make that worse.

also using bayer filter arrangements to do colour essentially throws away 2/3 of the light so we need to get away from that too. 3CCD and a prism would be good but bulky and expensive for a DSLR.

its easier to make a low res sensor more sensitive, because you can have bigger pixels, but i'm not clear that this new technology (whatever it is) will apply to hi res sensors.

the ultimate sensor would count individual photons digitally, with no saturation point, and recording the wavelength (colour) of each photon. (although given the trichromatic nature of the eye the latter might be overkill for human viewing)

although we are still a fair way away from that, I think that real world photon counts will always put a limit on what can be done with low light.

the eye can detect a single photon (although not in colour!) but our vision still gets fuzzy/grainy in low light.

so what's the point of the much touted 22bit A/D then?

or are they just "marketing bits" like we so often see in audio....

So - I think a lot about ISO and noise and camera design relating to those things because I take shots in low light.

Now as I understand it, the iso settings simply change the gain of the amplifier on the output of the CCD before it goes to the A/D converter.

that means that at all settings other than the slowest, the image will clip BEFORE the CCD saturates (for any given pixel), so we use progressively less of the dynamic range of the sensor as we increase ISO. no wonder the noise levels go up!

now the K10D has a 22bit a/d converter, thats significantly more steps of dynamic range than photons per pixel at the slowest ISO, in other words its massive overkill. (which is good)

so seems to me that if we used 16bit or better raw files we would be capturing the entire dynamic range of the CCD anyway, brightness would get adjusted later, we'd never clip the image at low light, there would be no need to ever set the ISO, it would become another of those many camera settings that only affects the jpg. (or gets adjusted automatically to create the jpg)

so why isn't this happening? seems like it might even be possible with a firmware update to the K10D?

or have I misunderstood something?