On Fri, Mar 5, 2010 at 3:21 AM, Rob Studdert <[email protected]> wrote: > On 05/03/2010, Larry Colen <[email protected]> wrote: > >> High ISO on it is amazing. ISO 6400 is actually usable. I need to find out >> how they do 12,800, whether that's done with circuitry, or just by >> underexposing at 6400 by a stop and correcting with math. > > All ISO's other than the native ISO is synthesized, regardless of > whether the effective ISO is arrived at via math or circuitry if the > supporting DAC is well matched it shouldn't really have any effect. >
Actually there's a definite difference between hardware ISO's (200-6400 on the K-x) and the expanded range ISO's achieved by DSP processing, The hardware ISO is achieved on-chip and fully benefits from the optimization of the signal path and any on-chip NR. This is why you see a definite difference between shooting at higher ISO's and shooting at low ISO's, underexposing and boosting in post. The difference is primarily in resolution of lower luminance values at the ADC level, since hardware ISO is achieved before the ADC, the ADC sees the full amplified signal, software ISO settings take the post-ADC data and bring it up via software and thus have to contend with the lower resolution of the shadow detail and increased noise that results from doing this (the vast majority of the luminance resolution from an ADC is in the higher values, low values are less well resolved and with software ISO you're boosting those lower values). -- M. Adam Maas http://www.mawz.ca Explorations of the City Around Us. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
