ISO 12233:2017 Edge SFR (eSFR) Photographic chart

Description

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Chart Sizes	Active Area	Megapixel Suitability *
1x	200mm × 305mm (7.875″ × 12″)	3.4mp
2x	400mm × 610mm (15.75″ × 24″)	13mp
4x	800mm × 1220mm (31.5″ × 48″)	54mp

* As measured to the interior of the black border.

ENHANCED VERSION

The Imatest Enhanced ISO 12233:2014 E-SFR chart has all the features of the Standard chart, keeping the 3:2 aspect ratio, with the addition of six added slanted squares for measuring performance near the image boundaries and hyperbolic wedges for visual analysis or analysis with the Imatest Wedge module. 

The differences between the Imatest charts and the chart illustrated in the standard are listed below. Even with these differences the Imatest chart is in full compliance with the standard.

• A 20-patch OECF grayscale pattern* is used as opposed to the 16-patch version.
• The Focus Patterns in the centers of the squares are rectangular (to increase the MTF measurement area) and are designed to reduce interference with automatic edge detection.
• There are four registration marks instead of three to facilitate automated region detection. (Four features are required for a projective transform.)
• An additional mark above the lower-left registration mark is used for detecting chart orientation.
   

The differences between the Enhanced and Standard Versions are as follows:

• Six extra slanted squares are added for measuring performance near the image boundaries.
• Several hyperbolic wedges with spatial frequencies, similar to the CIPA chart referenced in the ISO standard, for visual analysis or use with the Imatest Wedge module.
• 16 color patches when produced with technologies that allow color (inkjet or color LVT), with colors similar to the industry-standard 24-color test chart.
   

This chart will work with the fully-automated eSFR ISO module, starting with the Imatest 4.0 release.

 

Extended Version (not currently available)

The Imatest Extended ISO 12233:2014 E-SFR chart has all the features of the Enhanced chart (six extra squares, and wedges), but has a 16:9 aspect ratio, which makes it suitable for HDTV and cinema measurements (and it also works well with 3:2 aspect ratio DSLRs). It is fully compliant with the standard.

This chart will work with the fully-automated eSFR ISO module, starting with the Imatest 4.0 release.

 

Megapixel Quality Ratings

Megapixel suitability is based on analysis of Modulation Transfer Function (MTF) obtained from a chart image captured using a 1:1 magnification lens (Canon 65mm f/2.8 1-5x macro) and a 6.5µm pixel size sensor (Canon EOS 6D). In order to consider performance throughout the cameras range of expected sharpness, MTF90 (the spatial frequency where MTF is 90%) is weighted at 0.5, MTF70 is weighted at 0.35, and MTF50 is weighted at 0.15. Conversion to megapixels is based on the Imatest Chart Quality Index (CQI) calculation which determines sensor height suitability using the equation 2 * MTFxx (cycles per object mm) * vertical chart height (mm), where xx is 90, 70 or 50. Megapixel suitability calculations assume that (1) the lens is of high quality, (2) that the chart fills the vertical field of view (vFoV) of the camera system, and (3) that the sensor aspect ratio is 3:2. For 16:9 aspect ratio sensors (with pillarboxed framing, if applicable), multiply the megapixel suitability by 1.185. For 4:3 aspect ratio sensors (with left/right sides of chart cropped), multiply megapixel suitability by 0.889. Charts can be suitable for significantly higher megapixel counts if the minimum resolvable feature size of the lens is larger than the pixel size or the chart fills less than the full sensor vertical field of view.

Documentation and software support

eSFR ISO can be run either through the highly-interactive Rescharts interface or as a batch-capable fixed module. The key documentation for getting started is Using eSFR ISO Part 1, found in the eSFR ISO section of the Documentation page. Badly-framed charts can be analyzed with SFR using manual ROI selection.