> I think the actual sensors do have the 14-16 bits you mention - which > literally means that the max charge is up to some 65000 electrons. > However, they also have a readout noise of at least 10 electrons, > which > is equivalent to 3 or 4 bits. This essentially means that you are left > with a usable dynamic range or latitude equivalent to 12 bits; any > additional bits would just be "measuring the noise", if they contained > any information at all. That's why a 12-bit A/D is traditionally used. > > Furthermore, when you amplify the signal for a higher ISO setting, you > also amplify the noise, thus shifting up the 3 or 4 bits so that > contain > noise, so it enters even the 12 bits you keep. > > But like I said, this has been discussed a lot in the past few weeks. > In > in several rounds before that, too. Enough for now. > > I'm not sure I've read the data sheets of the *exact* sensors used in > the Pentax cameras, either, by the way (I've seen technical data for > various ones of similar type...) > > - Toralf
Hi, Yes, actually I was talking about usable bits, taking the noise into account, thus giving 14-16bits of usable data. This is so at least with the good quality astronomical ccd sensors but I am sure the DSLR camera sensors are coming close nowadays (or am I just hoping?). In any case, when designing measuring systems (using amplifiers and a/d converters) it is a good thing to have plenty of more bits and precision compared to the original signal. This way you will minimize the added noise. When having a 22 bits a/d converter on the K10D you can also measure and analyze the "noise" of the low expusure pixels. You will get all the available information out of the sensor. Antti-Pekka ________________________________________ Antti-Pekka Virjonen Computec Oy R&D Turku www.computec.fi -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
