Jeff and Lea: Another important aspect of working with histograms is the fact that the information displayed is not based on the RAW capture but rather on the JPEG preview instead. Since JPEGs are limited to 8-bit (format limitation) while RAW images are captured in 16-bit, it is very clear that a lot of the information captured is not being displayed by the histogram. So while the histogram may be showing blown highlights, a lot of the information that was clipped when the image was converted to JPEG to create the preview is still there in the RAW file to be explored and manipulated. Joseph Chamberlain ---------------------------------------------------------------------------- On 10/10/06 5:49 PM, "Jeff Spirer" <jeff@xxxxxxxxxx> wrote: > At 12:47 PM 10/10/2006, lea murphy wrote: >> I'm confused. >> >> Some shots show blown highlights in my histogram on my Canon 20D but when I >> pull then into Photoshop RAW converter I can adjust them so the highlights >> aren't blown at all. >> >> What gives? > > There is a simple explanation, and it is not that RAW can do magic, or that > RAW converters can pull out things that are not there. > > The 20D histogram shows only one channel. This channel is an approximation of > the luminance channel that you would see if the image was in HSL rather than > RGB. This luminance channel is formed from a specific averaging method > applied to all three channels. Because of this, it doesn't give you an exact > reading at the edges of the histogram, it only gives you an averaging. > > This is why newer (and often more expensive) cameras have an RGB histogram - > this is the only way to get accurate readings at the edges. This will always > be a problem with single channel histogram displays - they have to reduce the > information they give. > > >> I thought blown highlights meant there was no data in the highlights but >> indeed, I have plenty of info when I make a little exposure adjustment. >> >> Am I just lucky or is this normal? >> >> Lea >> >> >> >> lea murphy >> www.leamurphy.com <http://www.leamurphy.com/> >> www.whinydogpress.com <http://www.whinydogpress.com/> >> blog: web.mac.com/leamurphy <http://web.mac.com/leamurphy> >> >> > > Jeff Spirer > Photos: http://www.spirer.com > <http://www.spirer.com/> One People: http://www.onepeople.com/ > <http://www.onepeople.com/>
