Overview
ISO 18844:2017 - Photography - Digital cameras - Image flare measurement is an international standard developed by ISO for the photography industry. This standard provides a comprehensive method to define, measure, and compare image flare in digital cameras. Image flare refers to the unwanted increase in signal within a processed digital image caused by stray light that does not originate from the intended scene, impacting the overall image quality, particularly contrast and shadow details.
ISO 18844:2017 outlines the use of specific test charts, measurement conditions, and detailed procedures to objectively assess and report image flare in digital camera systems. The measurement process encompasses all factors contributing to image flare, such as lenses, camera body construction, image sensors, and in-camera image processing.
Key Topics
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Definition of Image Flare
Image flare is identified as the increase in image signal due to light detected by the sensor that does not correspond to a point in the photographed subject. This includes contributions from internal lens reflections, sensor artifacts, body-induced stray light, and image processing algorithms.
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Test Patterns and Charts
The standard specifies the design and usage of reflection-type and transparent-type charts, used for both single spot and multiple spot measurement. These charts feature specified ratios of black and white areas and are calibrated for uniformity and contrast.
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Measurement Conditions
ISO 18844:2017 details environmental and camera settings, such as:
- Standardized lighting (illuminance and luminance levels)
- Chart reflectance or transmittance properties
- Camera exposure settings, white balance, focus method, and, when relevant, lens hood use
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Measurement Types
The standard defines three types of measurement:
- Type A: For cameras with manual exposure, using high-contrast charts and variable exposures
- Type B: For cameras with automatic exposure, using consistent exposure across charts
- Type C: For very high contrast charts, applicable to both exposure control scenarios
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Result Presentation
Guidelines are provided for reporting results, including camera and chart details, exposure settings, measurement methodology, and output luma levels.
Applications
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Digital Camera Performance Assessment
Manufacturers and testing laboratories can utilize ISO 18844:2017 to objectively measure and compare image flare across different digital camera models. This assists in product development and quality assurance.
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Photography Equipment Benchmarking
The standard enables users, including reviewers and professional photographers, to make informed decisions by offering comparable flare measurements.
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Image Quality Optimization
Camera designers can analyze how different optical and electronic components, as well as image processing algorithms, influence image flare and can refine their products for improved image clarity.
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Standards Compliance and Documentation
Adoption of this standard facilitates conformance to recognized measurement practices, essential for technical specifications, marketing claims, and industry certifications.
Related Standards
- ISO 9358: Optics and optical instruments - Veiling glare of image forming systems - Definitions and methods of measurement
- ISO 12231: Photography - Electronic still picture imaging - Vocabulary
- ISO 18383: Photography - Digital cameras - Specification guideline
- IEC 61966-2-1: Multimedia systems and equipment - Colour measurement and management - Part 2-1: Default RGB colour space - sRGB
Practical Value
By following ISO 18844:2017, stakeholders across the digital imaging industry gain:
- Consistent test methodology for camera image flare
- Reliable data for product comparison and quality checks
- Industry-wide accepted criteria for image quality evaluation
Implementing the standardized image flare measurement supports innovation, transparency, and customer trust in the performance claims of digital cameras.