Stepchart: Applied Image and ISO charts

Applied Image and ISO charts

In addition to linear reflective and transmission step charts, Stepchart (in Imatest Pro) can analyze the tonal response and noise of a number of additional charts, all but one of which are available from Applied Image. These charts are described below.

QA-61 ISO-16067-1 Scanner

QA-62		QA-62 SLANT EDGE TARGET  Slant Edge Scanner Target with Grayscale SFR & OECF #2  Ideal for evaluation response of digital systems to the slanted sharp edge function and used for MTF analysis. Data: Size 75mm x 75mm (3in x 3in); 25mm dark grey square rotated (5 degree) on a light grey background; surrounded by 20 nine-mm square grey scale patches. Notes: Ideal for evaluation response of digital systems to the slanted sharp edge function and used for MTF analysis.  For full description, see QA-62 Product specifications. Part No. QA-62-SFR-P-RP Overall Size 95 x 76mm (3.75 x 3in) Material RP - photo paper
ST-51 EIA Grayscale		ST-51 EIA HALFTONE GRAY SCALE Data: The EIA grayscale pattern is a standard 2" square projection slide. It contains two parallel gray scales. The upper scale has nine nominally equal transmission steps while the lower contains the same number of nominally equal density steps. The transmission values range from 3% to 60%, corresponding to density values of 1.52 and 0.22 respectively. The slide is chrome on glass and densities are achieved by a fine halftone pattern. Densities can be found here.   Part No. ST-51-CG Overall Size 50mm x 50mm Material Reflective Material
ST-52 ISO-14524 12-patch OECF target (circular)		ST-52 ISO DIGITAL CAMERA CONTRAST CHART Data: This Camera Contrast Chart conforms to International Standard ISO-14524, Photography - Electronic Still Picture Cameras - Methods for Measuring Opto-Electronic Conversion Functions (OECF). Notes: Chart features 12 gray levels on a durable material. Densities range from 0.10 to 2.30.   Part No. ST-52-RM Overall Size 356mm x 200mm Material Reflective Material
ISO-15739 Noise target		Details on the I3A.org ISO Tools dowload page, particularly the ISO 15739 Noise Test Chart Utility
20-patch OECF targets (circular)		Several charts use this 20-patch arrangement. (upper) Portion of proposed low-contrast ISO 12233 chart When OECF 20-patch circular is selected in the input dialog box (below), one of the following chart contrasts should be selected in the box just below the OECF 20-patch radio button. TE 241 Available from Image Engineering/Esser Test Charts. Transmissive chart. 12600:1 contrast ratio. 0 ≤ density ≤ 4.1 Low contrast 20:1 From ISO/DIS 14524, Table A3. 0.1 ≤ density ≤ 1.4 Standard reflection 80:1 From ISO/DIS 14524, Table A3. 0.1 ≤ density ≤ 2.0 Normal contrast 160:1 From ISO/DIS 14524, Table A3. 0.1 ≤ density ≤ 2.3 High contrast 1000:1 From ISO/DIS 14524, Table A3. 0.1 ≤ density ≤ 3.1 (lower) Esser Test Charts TE241
ITE Grayscale		Comes in two versions: Type I: gamma = 0.45 and Type II: gamma = 1.0. Available from DNP (Japan), Zonetech (Korea), and Image Engineering/Esser Test Charts (Germany), where it is designated TE 83 and TE 84. When ITE Grayscale is selected in the input dialog box (below), either ITE Grayscale I: gamma = 0.45 or ITE Grayscale II: gamma = 1.0 should be selected in the box just above the ITE Grayscale radio button.

Instructions for Applied Image/ISO charts

Run Stepchart in the usual manner by clicking on Stepchart in the Imatest main window.

Select the approximate crop region, which should include the grayscale patches and no more. Ignore any crop or selection marks. The crop does not have to be accurate; a find adjustment dialog box will appear later. If the crop aspect ratio is less than 3:1, Stepchart recognizes the chart as one of the Applied Image/ISO charts.

Cropping illustration for the five targets The initial crop should include the grayscale patches and no more. It does not have to be accurate: after the chart type is selected,a fine adjustment dialog box appears. QA-61 ISO- 16067-1 Scanner QA-62 ST-51 EIA Grayscale ST-52 ISO-14524 12-patch OECF target ISO-15739 Noise target   20-patch OECF targets ITE Grayscale

The dialog box shown below appears. The cropped input image is shown on the right. Select the appropriate chart type using the radio buttons in the middle. The image on the left illustrates the chart type: the patches should match the input image on the right.

You can change the title if needed. You can select a file for reference density values if you choose not to use the standard values. The file should contain patch densities, one per line. The patch order is given below. The scaling box affects the x-axis and noise plots in Figures 2 and 3. It is identical to the standard Stepchart input dialog box. If you choose OECF 20-patch circular, choose one of the contrast settings listed in the above table.

If you click OK, the fine ROI selection box, shown below appears. You can move the entire ROI using one of the buttons on the top left:  ^ ,  v ,  < , or  > . You can move the top margin with  T ^  or  T v , the bottom margin with  B ^  or  B v , etc. Corners can also be adjust individually: useful in the presence of perspective or lens distortion. Author's note: I would have liked to be able to click and drag on lines or corners, but the limitations of the Matlab interface didn't allow this.

You can enter X and Y values for the corners (tl = top left, etc.): be sure to press Enter for each value if you do. The size of the selection is shown on the lower left. Fill factor (linear) (on the lower right, just above  No, Try again  ) sets the size of the squares. It defaults to 0.7. It can be increased to obtain more samples for noise analysis, but it may need to be reduced if the image is tilted or distorted.

When the squares have been adjusted, click  Yes, Continue ,  No, Try again , or  Cancel .

The Output is the same as for standard linear step charts.

Patch order for the five targets

The table below shows the patch order for the targets. Use this order when creating a custom density file.