Thanks Rob. I find that if I think of the data captured by the sensor as a piece of film it makes sense. The lightest areas, total white, can be made darker, but they contain no detail. The darkest areas, total black, can be made lighter, but they contain no detail. The only way those areas of the frame could contain meaningful information is to adjust exposure up or down at the time of capture, moving, as Godfrey terms it, the window.
Well, I think I understand it now (whethr it sounds like it or not). :-) Tom C. >From: "Digital Image Studio" <[EMAIL PROTECTED]> >Reply-To: Pentax-Discuss Mail List <[email protected]> >To: "Pentax-Discuss Mail List" <[email protected]> >Subject: Re: Silly HDR Question >Date: Sun, 5 Nov 2006 08:43:18 +1100 > >On 05/11/06, Tom C <[EMAIL PROTECTED]> wrote: > > If I take a RAW .PEF file and adjust exposure -1 and +1 stop, saving >each as > > another .PEF in Adobe Camera Raw, would that not for all intents and > > purposes, be the same as having taken three separate exposures at >-1/0/+1 ? > > > > Could I conceivably then process the three as an HDR and get the same > > results and have the same flexibility in post-processing as if I took >three > > exposures in-camera? > >Not even close Tom, if you have more than one frame at different >exposures you have an absolute differential of the difference between >the exposures beyond the absolute range of the RAW file. By carefully >controlling the adjustments during RAW conversion the entire latitude >of any exposure can be realised in a single conversion. If your RAW >converter doesn't have a curves tool then of course there is limited >scope to control the gamma via contrast if you need to push the >brightness to extremes. However if you generate a 16 bit output files >then fine gamma adjustments can be effected without loss in any >decent image editor using a curves tool. > >Of course the validity of even applying HDR techniques depends upon >the subject matter and lighting. IOW if the subject brightness range >lies within the latitude of a single exposure then the technique may >yield very marginal advantage. > >-- >Rob Studdert >HURSTVILLE AUSTRALIA >Tel +61-2-9554-4110 >UTC(GMT) +10 Hours >[EMAIL PROTECTED] >http://home.swiftdsl.com.au/~distudio//publications/ >Pentax user since 1986, PDMLer since 1998 > >-- >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
