1. An Evaluation of the Current State of Digital Photography Charles Dickinson Advisor: Jeff Pelz

2. Main Objective n Gain a better understanding of the state of digital photography

3. Overview n Introduction n Experimental n Results n Conclusions n Review

4. Introduction n Goal: Evaluate digital photography from digital camera input to printer output n Metrics: MTF and subjective evaluation

5. Questions to be Answered n Obtain a model for digital photography n What is gained by upgrading a camera / printer in a digital photographic system? n What are the effects of interline vs. frame transfer?

6. Experimental n Kodak DC120, DC260, DCS315, DCS460 n Epson Stylus 800, Kodak 8670 n Photoshop, IDL, Image Analyzer, Imlab

7. Digital Camera Characterization n Adopted slanted knife edge method n Software: PIMA Image Analyzer plug-in, ISO 12233

8. Image Analyzer n Calculates MTF given a slanted knife edge n Easy to use, robust edge angle, predicts MTF up to 4 times Nyquist frequency 1 1.)Benchmarking of the ISO 12233 Slanted-edge Spatial Frequency Response Plug-in, Don William, IS&T’s 1998 PICS Conference, pp 133-136 1.)Benchmarking of the ISO 12233 Slanted-edge Spatial Frequency Response Plug-in, Don William, IS&T’s 1998 PICS Conference, pp 133-136

9. Procedure n Image target in upright position n Convert image to Lab space and remove a and b channels in Photoshop n IDL program takes rectangle within reflectance targets and averages values (Digital Count, dc)

10. Target Image (DC260)

11. Procedure n Input dc values into Excel, plot vs. known reflectances n Fit trendline and calculate reflectances for 256 dc’s n In Photoshop, select ROI, use Image analyzer ‘filter’ n Image analyzer calls for ‘OECF’

12. Printer Characterization n IDL creates sine patterns, print in Photoshop n Examine under microdensitometer with Imlab n Determine MTF with histogram of sine pattern

13. Sine Histograms Reflectance # pixels idealreal Reflectance max max min min Modulation = (Rmax - Rmin) / (Rmax + Rmin)

14. Subjective Evaluation n Four questions: sharpness, color preference, color reproduction, overall quality n 1-10 rating n Image with DC120 and DCS460 printed on dye-sub and inkjet, traditional photograph n 5 x 7 inch prints

15. Subjective Image

16. Camera Results

17. Camera Discussion n DCS460 performs best, DC120 worst n DC260 has edge enhancement n DCS315 performed worse than DC260

18. Printer Results

19. Printer Discussion n Inkjet performs better than dye-sub n Due to binary nature of inkjet

20. Subjective Results: Overall

21. Subjective Results: Sharpness

22. Subjective Results: Color Preference

23. Subjective Results: Color Reproduction

24. Subjective Results Discussion n DCS460, inkjet combination did the best for sharpness, color, but 460, dye-sub system did better overall n Photograph didn’t perform best in any category n For DC120, inkjet and dye-sub perform about the same

25. System Results

26. System Results Discussion n DC260/inkjet system performed the best n For DC120, DCS315: printer makes small change in MTF n For DC260, DCS460: printer makes large change in MTF

27. Conclusions n Interline vs. frame transfer comparison can’t be done with DC260, DCS315 n For low end camera, printer upgrade is insignificant to MTF n High end camera MTFs benefit from printer upgrade n Although inkjet has better MTF, dye-sub is more pleasing to eye

28. Review n Gain model for digital photographic systems n Accomplished, but: – MTF doesn’t completely describe system – Subjective evaluations for DC120, DCS460 only

29. Special Thanks Dr. Jeff Pelz Dr. Jeff Pelz Dr. John Arney Dr. John Arney