An Evaluation of the Current State of Digital Photography Charles Dickinson Advisor: Jeff Pelz.
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Transcript of An Evaluation of the Current State of Digital Photography Charles Dickinson Advisor: Jeff Pelz.
An Evaluation of the An Evaluation of the Current State of Current State of
Digital PhotographyDigital Photography
Charles Dickinson Charles Dickinson
Advisor: Jeff PelzAdvisor: Jeff Pelz
Main ObjectiveMain Objective
Gain a better Gain a better understanding of the state understanding of the state of digital photographyof digital photography
OverviewOverview
IntroductionIntroduction ExperimentalExperimental ResultsResults ConclusionsConclusions ReviewReview
IntroductionIntroduction
GoalGoal: Evaluate digital : Evaluate digital photography from digital photography from digital camera input to printer camera input to printer outputoutput
MetricsMetrics: MTF and subjective : MTF and subjective evaluationevaluation
Questions to be Questions to be AnsweredAnswered
Obtain a model for digital Obtain a model for digital photographyphotography
What is gained by upgrading a What is gained by upgrading a camera / printer in a digital camera / printer in a digital photographic system?photographic system?
What are the effects of interline What are the effects of interline vs. frame transfer?vs. frame transfer?
ExperimentalExperimental
Kodak DC120, DC260, Kodak DC120, DC260, DCS315, DCS460DCS315, DCS460
Epson Stylus 800, Kodak 8670Epson Stylus 800, Kodak 8670 Photoshop, IDL, Image Photoshop, IDL, Image
Analyzer, ImlabAnalyzer, Imlab
Digital Camera Digital Camera CharacterizationCharacterization
Adopted slanted knife edge Adopted slanted knife edge methodmethod
Software: PIMA Image Analyzer Software: PIMA Image Analyzer plug-in, ISO 12233plug-in, ISO 12233
Image AnalyzerImage Analyzer
Calculates MTF given a slanted Calculates MTF given a slanted knife edgeknife edge
Easy to use, robust edge angle, Easy to use, robust edge angle, predicts MTF up to 4 times Nyquist predicts MTF up to 4 times Nyquist frequencyfrequency11
1.)1.)Benchmarking of the ISO 12233 Slanted-edge Spatial Frequency Response Plug-inBenchmarking of the ISO 12233 Slanted-edge Spatial Frequency Response Plug-in , Don , Don
William, IS&T’s 1998 PICS Conference, pp 133-136William, IS&T’s 1998 PICS Conference, pp 133-136
ProcedureProcedure
Image target in upright positionImage target in upright position Convert image to Lab space and Convert image to Lab space and
remove a and b channels in remove a and b channels in PhotoshopPhotoshop
IDL program takes rectangle within IDL program takes rectangle within reflectance targets and averages reflectance targets and averages values (Digital Count, dc)values (Digital Count, dc)
Target Image (DC260)Target Image (DC260)
ProcedureProcedure
Input dc values into Excel, plot vs. Input dc values into Excel, plot vs. known reflectancesknown reflectances
Fit trendline and calculate Fit trendline and calculate reflectances for 256 dc’sreflectances for 256 dc’s
In Photoshop, select ROI, use In Photoshop, select ROI, use Image analyzer ‘filter’Image analyzer ‘filter’
Image analyzer calls for ‘OECF’Image analyzer calls for ‘OECF’
Printer CharacterizationPrinter Characterization
IDL creates sine patterns, print IDL creates sine patterns, print in Photoshopin Photoshop
Examine under Examine under microdensitometer with Imlabmicrodensitometer with Imlab
Determine MTF with histogram Determine MTF with histogram of sine patternof sine pattern
Sine HistogramsSine Histograms
ReflectanceReflectance
# pixels# pixels
idealideal realreal
ReflectanceReflectance
# pixels# pixelsmaxmax maxmaxminmin minmin
Modulation = (Rmax - Rmin) / (Rmax + Rmin)Modulation = (Rmax - Rmin) / (Rmax + Rmin)
Subjective EvaluationSubjective Evaluation
Four questions: sharpness, color Four questions: sharpness, color preference, color reproduction, overall preference, color reproduction, overall qualityquality
1-10 rating1-10 rating Image with DC120 and DCS460 printed Image with DC120 and DCS460 printed
on dye-sub and inkjet, traditional on dye-sub and inkjet, traditional photographphotograph
5 x 7 inch prints5 x 7 inch prints
Subjective ImageSubjective Image
Camera ResultsCamera Results
Camera DiscussionCamera Discussion
DCS460 performs best, DC120 DCS460 performs best, DC120 worstworst
DC260 has edge enhancementDC260 has edge enhancement DCS315 performed worse than DCS315 performed worse than
DC260DC260
Printer ResultsPrinter Results
Printer DiscussionPrinter Discussion Inkjet performs better than dye-subInkjet performs better than dye-sub Due to binary nature of inkjetDue to binary nature of inkjet
Subjective ResultsSubjective Results:: Overall Overall
Subjective ResultsSubjective Results::SharpnessSharpness
Subjective ResultsSubjective Results: : Color Color PreferencePreference
Subjective ResultsSubjective Results:: Color Color ReproductionReproduction
Subjective Results Subjective Results DiscussionDiscussion
DCS460, inkjet combination did the DCS460, inkjet combination did the best for sharpness, color, but 460, best for sharpness, color, but 460, dye-sub system did better overalldye-sub system did better overall
Photograph didn’t perform best in Photograph didn’t perform best in any categoryany category
For DC120, inkjet and dye-sub For DC120, inkjet and dye-sub perform about the sameperform about the same
System ResultsSystem Results
System Results System Results DiscussionDiscussion
DC260/inkjet system performed DC260/inkjet system performed the bestthe best
For DC120, DCS315: printer For DC120, DCS315: printer makes small change in MTFmakes small change in MTF
For DC260, DCS460: printer For DC260, DCS460: printer makes large change in MTFmakes large change in MTF
ConclusionsConclusions Interline vs. frame transfer comparison Interline vs. frame transfer comparison
can’t be done with DC260, DCS315can’t be done with DC260, DCS315 For low end camera, printer upgrade is For low end camera, printer upgrade is
insignificant to MTFinsignificant to MTF High end camera MTFs benefit from High end camera MTFs benefit from
printer upgradeprinter upgrade Although inkjet has better MTF, dye-sub Although inkjet has better MTF, dye-sub
is more pleasing to eyeis more pleasing to eye
ReviewReview
Gain model for digital photographic Gain model for digital photographic systemssystems
Accomplished, but:Accomplished, but:– MTF doesn’t completely describe MTF doesn’t completely describe
systemsystem
– Subjective evaluations for DC120, Subjective evaluations for DC120, DCS460 onlyDCS460 only
Special ThanksSpecial Thanks
Dr. Jeff Pelz Dr. Jeff Pelz
Dr. John ArneyDr. John Arney