imatest史上最详细教程

imatest史上最详细教程 Imatest史上最详细教程 2009 Imatest LLC Imatest Documentation 1 of 451 Imatest Documentation Image Quality An overview of the key image quality factors and how they are measured by Imatest Sharpness - What is it and how is it measured? Introduction - The Slanted-edge test - Calculation details - Results - Interpreting MTF50 SQF - Subjective Quality Factor Introduction - SQF and MTF - Meaning of SQF - Measuring SQF - The SQF equation - CSF - Links Noise in photographic images Introduction - Appearance - Noise measurements - Noise summary - F-stop noise - The mathematics of noise - Links Sharpening - Why standardized sharpening is needed for comparing cameras Standardized sharpening - Examples Sharpness comparisons - for several digital cameras Introduction - Explanation of results - Tables of results - Interpretation of MTF - Some observations - Links Chromatic Aberration - AKA Color fringing Introduction - Measurement - Demosaicing Veiling glare (Lens flare) Introduction - Target - Measurement - Results - ISO 9358 Color correction matrix Introduction - Math - Multicharts ISO Sensitivity and Exposure Index Introduction - Modules - Equations - RAW files - Related documents Shannon information capacity - information that can pass through a channel without error Meaning - Results - Summary Blur units, MTF, and DXO Analyzer's BxU The Imatest Test Lab - How to build a testing lab Introduction - Hardware - Lighting - Easel - Light measurement - Tripod - Clamps - Putting it together - Targets - Aligning target & camera Imatest Instructions -- General Installation - and getting started Install - Purchase - Register - Offline registration - Files Using Imatest Running Imatest - multi_read - RAW files - Other controls - Pulldown menus - Figures - .CSV and XML output - Use of Imatest RAW files Introduction - Using RAW files - Bayer RAW - dcraw demosaicing - Rawview utility - Generalized Read Raw The Imatest Test Lab - How to build a testing lab Introduction - Hardware - Lighting - Easel - Light measurement - Tripod - Clamps - Putting it together - Targets - Aligning target & camera Troubleshooting - What to do when Imatest doesn't work Installation problems - Problems after install - Missing DLLs - Runtime problems - INI files - Command (DOS) window - Diagnostics runs - Path conflicts Imatest Instructions -- Sharpness modules Using SFR Part 1 - Setting up and photographing SFR targets Slanted-edge test - Print chart - Lighting - Distance - Exposure - Tips - Quality and Distance Using SFR Part 2 - Running Imatest SFR Image file - ROI - Additional input - Equations - Gamma - Warnings - Saving - Repeated runs - Excel CSV output Imatest SFR LCD target Screen Patterns module - Web pattern SFR results: MTF (Sharpness) plot SFR results: - Chromatic Aberration, Noise, and Shannon capacity plot SFR results: Multiple ROI (Region of Interest) plot 2D Summary plot - 1D Summary plot - CSV Output file - Summary explanation - Excel plots Using SFRplus Part 1 - The SFRplus chart: features and how to photograph it Slanted-edge test - Advantages - Obtain chart - Print chart - Lighting - Distance - Exposure - Tips - Quality and Distance Using SFRplus Part 2 - Running Imatest SFRplus Running SFRplus - Rescharts - SFRplus settings windows - Parameters & setup window - Settings & options window - Gamma - Warnings - SFRplus summary Imatest Documentation 2 of 451 Using SFRplus Part 3 - Imatest SFRplus results SFRplus results - Saving - Repeated runs - Excel .CSV (Comma Separated Values) output Using Rescharts - Analysis of resolution-related charts Introduction - Getting started - The Rescharts window - Rescharts modules - Slanted-edge SFR - Log frequency (simple) - Log frequency-contrast Log Frequency - Analysis of log frequency-varying charts Introduction - Photographing, running - Color moire - Output - Pattern - MTF - Comparisons - Calculation details - Nyquist, aliasing Log F-Contrast - Analysis of charts that vary in log frequency and contrast Introduction - Creating, printing - Photographing, running - Output - Pattern - MTF - MTF/contrast contours - MTFnn Star Chart - Analysis of the Siemens star chart Introduction - Creating, photographing, running - Output - MTF - MTFnn, MTFnnP - MTF contours - Equations MTF Compare - Compare MTFs of different cameras and lenses Introduction - Instructions Batchview - Postprocessor for viewing summaries of SFR, SFRplus results Introduction - Preparation - Instructions How to Test Lenses with SFRplus Introduction - Test chart - Photograph - Run SFRplus - Rescharts SFRplus - SFRplus settings - Interpret the results - Batches - Checklist How to Test Lenses with SFR - (old page: Imatest SFRplus recommended) Introduction - Test target - Photograph - Run SFR - Interpret - Checklist Imatest Instructions -- Tone, color, and spatial modules Using Stepchart Photographing the chart - Running Stepchart - Output - Saving - Dynamic range - Algorithm Stepchart: Applied Image and ISO charts Photographing chart - Instructions - Patch order Dynamic Range - Calculate Dynamic Range from several Stepchart images Introduction - Operation - Results - Dynamic Range bkgnd Using Colorcheck What Colorcheck does - Colorchecker colors - Photographing target - Photographing target - Colorchecker reference sources - Output - Saving - Links Colorcheck Appendix - Algorithms and reference formulas Color error formulas - Algorithm - Grayscale and exposure Using Multicharts - Interactive analysis of several test charts Introduction - Getting started - Reference files - The Multicharts window - Displays and options Multicharts Special Charts - Additional charts, including circles arranged on a square Instructions - Patch numbering - Examples Color correction matrix Introduction - Math - Multicharts Using Uniformity (Light Falloff) - Measures light falloff (lens vignetting) and sensor nonuniformity Instructions - Results Uniformity (Light Falloff): Imatest Master - Instructions for Imatest Master Input dialog box - Hot and dead pixels - Color shading - Uniformity profiles - Polynomial fit - Histograms - Noise detail - Spot detection Using Distortion Introduction - Instructions - Results - Main figure - Decentering - Corrected image - Intersection figure - Radius correction fig - Links - Algorithm Imatest Instructions -- Miscellaneous modules and utilities Using Test Charts - Creates test charts for high quality inkjet printers Introduction - Bitmap patterns - SVG patterns - Options Using Screen Patterns - Monitor patterns for Light Falloff, SFR, Distortion, and monitor calibration Introduction - Light Falloff - SFR - Distortion - Monitor calibration - Monitor gamma - Zone plate - SMPTE color bars - Slanted edges - Colorchecker- Stepchart - Squares (checkerboard) SVG Test Charts - Scalable Vector Graphics charts for MTF measurements Introduction: m x n squares - Squares and wedges - Operation - Options - Output figure - Printing View/Rename Files - using EXIF data Starting - 1. Select folder - 2. Select files - 3. Rename options - 4. Preview - 5. Rename files Imatest IT/EXE instructions - Running Imatest IT (Industrial Testing)/EXE Introduction - Installation - Setup - INI files - DOS call - Calling from Matlab - Testing - Error handling Using Print Test - Measure print quality factors: color response, tonal response, and Dmax Introduction - Instructions - Results Maskfill - Removes features that interfere with Imatest measurements Imatest Documentation 3 of 451 Introduction - Instructions Appendix Cross-reference tables - Tables to help you navigate Imatest Suppliers - Image quality factors - Image quality factors - Modules - Test charts - Test images Version comparisons - Differences between versions. Which is right for you? Glossary Glosario en Espanol Troubleshooting - What to do when Imatest doesn't work Installation problems - Problems after install - Missing DLLs - Runtime problems - INI files - Command (DOS) window - Diagnostics runs - Path conflicts Imatest Change Log - Imatest release history XML Changes - New XML improvements in Imatest 3.5.1+ Complete PDF documentation - The whole docs 14 MB and almost 500 pages, updated occasionally License - The Imatest End User License Agreement (EULA) Imatest Documentation 4 of 451 Image Quality Sharpness What is it and how is it measured? Image sharpness Sharpness is arguably the most important photographic image quality factor: it's the factor most closely related to the amount of detail an image can render. But it's not the only important factor. Imatest measures a great many others. Sharpness is defined by the boundaries between zones of different tones or colors. It is illustrated by the bar pattern of increasing spatial frequency, below. The top portion represents a target used to test a camera/lens combination. It is sharp; its boundaries are abrupt, not gradual. The bottom portion illustrates the effect of a high quality 35mm lens on a 0.5 millimeter long image of the pattern (on the film or digital sensor plane). It is blurred. All lenses, even the finest, blur images to some degree. Poor lenses blur images more than fine ones. One way to measure sharpness is to use the rise distance of the edge, for example, the distance (in pixels, millimeters, or fraction of image height) for the pixel level to go from 10% to 90% of its final value. This is called the 10-90% rise distance. Although rise distance is a good indicator of image sharpness, it has one limitation. It is poorly suited for calculating the sharpness of a complete imaging system from the sharpness of its components, for example, from a lens, digital sensor, and software sharpening algorithm. To get around this problem, measurements are made in frequency domain, where frequency is measured in cycles or line pairs per distance (typically millimeters in film measurements, but may also be inches, pixels, or image height). Line pairs per millimeter (lp/mm) is the most common spatial frequency unit for film, but cycles/pixel is convenient for digital sensors. The image below is a sine wave— a pattern of pure tones— that varies from low to high spatial frequencies, in this case from 2 to 200 lp/mm, over a distance of 0.5 millimeters. The top portion is the original sine pattern. The bottom portion illustrates the effects of the same high quality 35mm lens, which reduces pattern contrast at high spatial frequencies. The relative contrast at a given spatial frequency (output contrast/input contrast) is called the Modulation Transfer Function (MTF) or Spatial Frequency Response (SFR). Illustration of Modulation Transfer Function (MTF) (Spatial frequency response (SFR) ) Imatest Documentation 5 of 451 Green is for geeks. Do you get excited by a good equation? Were you passionate about your college math classes? Then you're probably a math geek— a member of a misunderstood but highly elite fellowship. The text in green is for you. If you're normal or mathematically challenged, you may skip these sections. You'll never know what you missed. The upper plot displays the sine and bar patterns: original and after blurring by the lens. The middle plot displays the luminance of the bar pattern after blurring by the lens (the red curve). Contrast decreases at high spatial frequencies. The lower plot displays the corresponding MTF (SFR) curve (the blue curve). By definition, the low frequency MTF limit is always 1 (100%). For this lens, MTF is 50% at 61 lp/mm and 10% at 183 lp/mm. Both frequency and MTF are displayed on logarithmic scales with exponential notation (10 0 = 1; 10 1 = 10; 10 2 = 100, etc.). Amplitude is displayed on a linear scale. The beauty of using MTF (Spatial Frequency Response) is that the MTF of a complete imaging system is the product of the the MTF of its individual components. MTF is related to edge response by a mathematical operation known as the Fourier transform. MTF is the Fourier transform of the impulse response— the response to a narrow line, which is the derivative (d/dx) of the edge response. Fortunately, you don't need to understand Fourier transforms or calculus to understand MTF. Traditional "resolution" measurements involve observing an image of a bar pattern (usually the USAF 1951 chart) on film, and looking for the highest spatial frequency (in lp/mm) where a pattern is visible. This corresponds to an MTF of about 5-10%. Because this is the spatial frequency where image information disappears— where it isn't visible, it is not a good indicator of image sharpness. Experience has shown that the best indicators of image sharpness are the spatial frequencies where MTF is 50% of its low frequency value (MTF50) or 50% of its peak value (MTF50P). MTF50 or MTF50P are ideal parameters for comparing the sharpness of different cameras for several reasons: (1) Image contrast is half its low frequency or peak values, hence detail is still quite visible. (2) The eye is relatively insensitive to detail at spatial frequencies where MTF is low: 10% or less. (3) The response of virtually all cameras falls off rapidly in the vicinity of MTF50 and MTF50P. MTF50P may better for oversharpened cameras that have peaks in their MTF response. Although MTF can be estimated directly from images of sine patterns (see Rescharts Log Frequency, Log F-Contrast, and Star Chart), a sophisticated technique, based on the ISO 12233 standard, "Photography - Electronic still picture cameras - Resolution measurements," provides more accurate and repeatable results. A slanted-edge image, described below, is photographed, then analyzed by Imatest SFR or Rescharts Slanted-edge SFR. (SFR stands for Spatial Frequency Response.) Origins of Imatest SFR The algorithms for calculating MTF/SFR were adapted from a Matlab program, sfrmat, written by Peter Burns ( ) to implement the ISO 12233 standard. Imatest SFR incorporates numerous improvements, including improved edge detection, better handling of lens distortion, a nicer interface, and far more detailed output. The original Matlab code is available on the I3A ISO tools download page by clicking on ISO 12233 Slant Edge Analysis Tool sfrmat 2.0. In comparing sfrmat 2.0 results with Imatest, note that if no OECF (tonal response curve) file is entered into sfrmat, it assumes that there is no tonal response curve, i.e., gamma = 1. In Imatest, gamma is set to a default value of 0.5, which is typical of digital cameras. To obtain good agreement with sfrmat, you must set gamma to 1. The slanted-edge test for Spatial Frequency Response Slanted-edge test charts can be created with Imatest Test Charts (SVG charts are especially recommended) or downloaded from How to test lenses with Imatest. The bitmap chart has horizontal and vertical edges for best print quality. It should be Imatest Documentation 6 of 451 tilted (about 2-8 degrees) before it is photographed. Imatest SFR can also take advantage of portions of the ISO 12233 test chart, shown on the right, or a derivative like the Applied Image QA-77, or as a less expensive alternative from Danes-Picta in the Czech Republic (the DCR3 chart on their Digital Imaging page)). Two such portions are indicated by the red and blue arrows. ISO 12233 charts are used in imaging-resource.com and dpreview.com digital camera reviews. A printable vector-graphics version of the ISO chart is available courtesy of Stephen H. Westin of the Cornell University Computer Graphics Department. It should be printed as large as possible (24 inches high if possible) so edge sharpness is not limited by the printer itself. (There may be some jaggedness in the slanted edges; not a problem with the recommended printable target.) A typical portion is shown on the right: a crop of a vertical edge (slanted about 5.6 degrees), used to calculate horizontal MTF response. An advantage of the slanted edge test is that the camera-to-target distance isn't critical. It doesn't enter into the equation that converts the image into MTF response. Imatest Master can calculate MTF for edges of virtually any angle, though exact vertical, horizontal, and 45? can have numerical problems. Slanted edge algorithm (calculation details) The MTF calculation is derived from ISO standard 12233. Some details are contained in Peter Burns' SFRMAT 2.0 User's