Although several of us have tried to come up with alternatives to buying a good "spectro" (using the abbreviated term generically and non-technically), and these methods can work reasonably well, my Datacolor Spyder Print remains one of the best investments I've ever made in photo equipment.
Paul
On Sun, Oct 18, 2015 at 12:26 AM, unesco18@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
After one month of trying to linearize with my scaner I made the following observations:
1) PK RAW profile from QTR is perfectly linear, as for my eye, looking at concentric grayscale circles test charts. Tetenal satin/pearl papers.2) Applying linearisation with use of Q13 test chart, scanner and QTR-StepWedge-Tool.zip makes the profile not only too dark as described in my original post but also non linear. Clearly visible bumps on concentric grayscale circles test.3) I repeated the procedure of linearisation with studio flash lamps (5500 K) and digital camera (EOS 6D) instead of my scanner. RAW file, PS CC 2015 processing: results very DIFFERENT than using my scanner. Shape of the curve is like for different type paper. In theory it should give the same results since I cmpare Q13 reference with printed 21 step wedge.4) Surprisingly, using scaner, numerical results of the output of L as computed by QTR-StepWedge-Tool are very linear after linearisation! But my eyes sey something different...Conclusions: there is no conclusion, I am totally messed up, maybe QTR-StepWedge-Tool code has some bugs? Any ideas that would help me? Certainly, I make a mistake somewhere, but can't find it.