On 24/07/2009, Bob W <p...@web-options.com> wrote: > As an aid to exposure a histogram based on the raw data should, if my > understanding is correct, be more accurate than one based on a jpeg. > However, my guess is that the accuracy of the output is limited by the > resolution of the display on the back of the camera, which is much smaller > than is likely to be available on your computer. So although the camera > could easily calculate the histogram from the many megapixels of raw data > available to it, it would then have to start removing accuracy to be able to > display it, so it needs a set of rules to decide how to reduce the accuracy > of the output. Perhaps using a jpeg conversion is that set of rules. This is > purely guesswork, but it seems to make some kind of sense to me.
The histogram will only ever be a rough representation of the luminance levels as there aren't enough horizontal pixels on the display to cover the luminance levels that the camera can record. The practical problem is that the on-camera histogram is representative of the RAW data constrained by the JPG engine gamut and WB selections rather than a representation of the actual sensors black point and saturation levels. That type of data would be useful. -- Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC +10 -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
