> from: Thomas Holm / Pixl <[EMAIL PROTECTED]> > date: Tue, 23 Dec 2003 11:06:03 > to: [EMAIL PROTECTED] > subject: Re: [PRODIG] Sinar captureshop > > Mike Russell wrote: > > > It's a shame Sinar don't include a "true" curve > > in their Standard Curve set. > > What is a "true" curve? One that doesn't suppress highlight and shadow > regions (like sholder and toe on film)? A lot of other stuff is going on > behind the scenes in regard to mapping tonal values to pleasing values, and > trust me, you don't want to miss out on those. A lot of work also goes into > making the tonal response similar to the human eye, and various CCD/CMOS > sensors with huge differences in sensitivity for various spectras (think UV > and IR light). The curve is simply a tool giving you a bit of control over > your images instead of it being a "done deal". > > > Since the colour > > calibration process involves shooting a known > > target (Macbeth 240 patch) you'd think it'd be > > possible to produce a file/curve where the > > readable values of the patches on screen > > correspond to their actual values on the chart. > > Supposing the goal of the camera manufacturer would be to reproduce a DC > ColorChecker as true as possible (and ignore all colours more saturated than > that and a few other minor things such as skin-tone contrast and > highlight/shadow definition) it is sort of possible. > > It's probably unlikely to be implemented for obvious reasons though. > > The only company in the world interested in a perfect representation of the > DC ColorChecker is the company manufacturing it namely GretagMacbeth (OK > include Munsel then). Most camera (and film) manufacturers are more > interested in pleasing colours and nice looking images. What pleasing > colours is, of course, is somewhat subjective. But so is the colour you > obtain from different brands of film and digital cameras... > > Another small issue is that you'd have to read the colour patches in Lab > (the reference you want to compare it to), and to be able to compare colours > would need to compare the values in Lab. This would require an Absolute > colorimetric conversion from Sinar RGB (whatever that may be on your > particular back) to D50 Lab. > > Oh, and we are discounting observer/camera metamerism, and gloss appearance, > from that equation too. > > It may sound tempting and easy Mike, but it isn't. > > The first time I went down that rabbit hole (in '93 on a Leaf DCB I "brick") > I spend 2-3 month on an off with a really good scanner operator, creating a > CMYK conversion in "Photone" and ColorShop that would yield a perfect > cromalin of a Macbeth 24 chart. We eventually succeeded within a percent or > two. > > However when we tried to actually convert real images they fell totally > apart with weird posterization, shadows closing down, greybalance skewed > etc. results were totally unusable for anything real life - but it was spot > on for the ColorChecker... > > Morale: > We didn't (and still doesn't) make a living shooting colour checkers, so > using that as a base for defining how a conversion should be done wasn't > (and still isn't) a wise decision... There are other more important > considerations than matching a set of colours no one (Ok, so no one except > you Mike <VBG>) cares about... > > Merry christmas > > > > Best Regards > > Thomas Holm / Pixl ApS > > - Photographer & Colour Management Consultant > - Adobe Certified Training Provider in Photoshop? > - Apple Solutions Expert - Colour Management > - Imacon Authorized Scanner Training Facility > - Remote Profiling Service (Output ICC profiles) > - Seminars speaker and tutor on CM and Digital Imaging etc. > > - Home Page: www.pixl.dk ? Email: th[AT]pixl.dk > -- > > > =============================================================== > GO TO http://www.prodig.org for ~ GUIDELINES ~ un/SUBSCRIBING ~ ITEMS for SALE
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