My point is that the profile needs to be applied before the data enters the digital domain, early in the a/d conversion. It needn't matter that the voltage rise is squared (if that's what you mean) as the brightness rises, as long as it's a constant and predictable relationship between photons in and voltage out. All that matters is that the profile is applied while it's still a voltage readout, not after it's become bits and bytes.
I am using "brightness" because that's what the light levels are commonly named in image editors. In Sensitometry/Densitometry class it was simply called "exposure" and "density". I still find myself referring to density even where digital images are concerned. Regards, Anthony Farr > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ryan > Brooks > Sent: Friday, 18 August 2006 2:55 PM > To: Pentax-Discuss Mail List > Subject: Re: Tonal gradation in shadows - The $67 Question? > > Anthony Farr wrote: > > Another thought. Why would converting the linear CCD output to non-linear > > A/D output have "not as much (good) information"? I could understand this > > if the CCD was outputting digital information and arbitrarily reassigning > > the values caused stairstepping type errors, but the CCD is analogue. What > > it's outputting is voltages. Can't the conversion be profiled? > > > > Regards, > > Anthony Farr > > > > > Sure... but a log/log representation would start to have big rounding > effects at each higher "stop"; in other words, it would be stair > stepping right past data as it moved up the curve. > > If the CCD recorded an apparent doubling in "brightness" as a doubling > in voltage your scheme would work great (like film). But it doesn't. A > doubling in "brightness" represents a four-fold increase in charge. > (whereas your film, our eyes, etc. see this as 2x) > > I don't like the word brightness. It makes this discussion difficult. > > I really dont think Pentax has solved this problem. Even if they do > have some sort of built-in gamma a/d conversion- what does it matter if > it's in hardware or software once you're in the digital domain? This > was all figured out years ago w/ video. > > References: > > http://www.normankoren.com/digital_tonality.html > http://en.wikipedia.org/wiki/Gamma_correction > > -R > > > -R > > > > >> -----Original Message----- > >> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of > >> > > Ryan > > > >> Brooks > >> Sent: Friday, 18 August 2006 1:22 PM > >> To: Pentax-Discuss Mail List > >> Subject: Re: Tonal gradation in shadows - The $67 Question? > >> > >> Except that the sensor is linear- if it's a CCD anyway. It's a photo > >> (okay, electron) counter. If you digitize the output in a non-linear > >> space, you're not getting as much (good) information as if it was a > >> linear digitization. > >> > >> -- > >> PDML Pentax-Discuss Mail List > >> [email protected] > >> http://pdml.net/mailman/listinfo/pdml_pdml.net > >> > > > > > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
