733667-001-011-0119
AI Summary
This document outlines technical guidelines for the evaluation and quality control of digital imaging, focusing on the digitization of cultural heritage materials. It discusses various metrics and definitions related to digital imaging, including color accuracy, exposure accuracy, and the impact of environmental factors on imaging quality.
Key Findings
- Discusses the importance of tone transfer functions and color rendering in digital imaging. - Defines key metrics such as exposure index and color accuracy. - Identifies potential causes of imaging failures, including calibration issues and environmental factors. - Emphasizes the need for proper white balance and color profile selection.
OCR Text
Federal Agencies Digitization Initiative Still Image Working Group — August 2010 Part II - Evaluation and Quality Control of Digital Imaging - SIGNAL - OECF — Opto Electronic Conversion Function ( ISO 14545) TTF — Tone Transfer Function TRC — Tone Reproduction Curve definition : Average large area digital response of an electronic imaging device to light stimuli 2 LB GB i Sensitivity (ISO 12232) Gefinition: The reciprocal of the amount of light necessary to Derivative Metrics ne and S definition : characteristic behavior of large area digital output response ( count value) to spectrally neutral White Balance/Neutrali definition : equivalence of large area color channel! output responses to a range of spectrally neutral input stimuli Color Encoding/Rendering cefinition: The difference between selected physically measured input colors and their achieve a desired output input stimuli ( gray patch) intended output rendering from a given color response. space. ~ Responsivity = Too dark/light - Color cast ~ Over/under saturated colors Y = Speed - Under/over exposed « Gray balance = Color balance is wrong =| ~ Exposure Index (EI) ~ No shadow/highlight detail - Memory colors are not correct 5 - Clipping — Color Accuracy = Contrast — Color Saturation iw ~ Exposure Accuracy >E @: Saturation based speed @: Average, median, maximum or @: Average, median, maximum, or RMS Qs RMS deviation from aim for neutral deviation from aim for chromatic patches of § units: TBD patches of interest. @: Average, median, maximum, or interest os units: Count Values, AL*, Density, F- RMS deviation from aim between color ; D : stops channels ( R-G, R-B, G-B ) for neutral Units (@): Count Values, Delta E (AE), Delta 5 2 | ~: Noise based speed : Deviation from a reference OECF | Patches of interest. E (AE,*ps), c units: TBD mma value s _ ga u Units (®): Count Values, AEssps, Units (7): Delta C, Delta H =F O: Exposure Index, Standard | units: gamma ( unitless) Units (‘@): Delta C, Delta H Ss 2 Output Sensitivity - Inefficient imaging detector Possible failure Causes ~—Auto-contrast failures -Inappropriate black/white point calibration. - Wrong gamma selection or tone aim — Poor auto-white balance algorithm - Bad white /black point calibration — Sparse gray patch balancing — Color Balance — Strongly colored environmental surround ~ Color profile tweaked for preference ~ Wrong color profile intent ~- Wrong color profile chosen/embedded - Color profile assumptions inconsistent with practice (i.e. lighting quality, gamma, intent, etc.) - Environmental : highly chromatic color surround/dothing Technical Guidelines for Digitizing Cultural Heritage Materials: Creation of Raster Image Master Files
Metadata
- Agency
- —
- Classification
- UNCLASSIFIED
- Department
- National Archives and Records Administration
- Catalog source
- View NARA catalog record
NARA Source
- NAID
- 733667
- File
- 733667-001-011-0119.jpg
- Type
- image/jpeg
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