Documentation

Stepchart: Special and ISO charts

In addition to linear step charts (which have a single row of patches), three modules (in Imatest Master and Image Sensor)— Stepchart, Multicharts, and Multitest— can analyze the tonal response and noise of a number of additional grayscale charts (reflective and transmissive), most of which are available from the Imatest Store.

These charts are described below.

Imatest Transmissive 36-patch Dynamic Range Chart
36 density patches with density steps of approximately 0.1, ranging from base density to base+3.4 (a much higher density range than reflective charts can achieve). A nearly circular patch arrangement ensures that vignetting has minimal effect on results. the chart has an active area of 7.75×9.25 inches on 8×10 inch film. A reference file with actual densities is supplied.

It also contains 4:1 contrast slanted edges for measuring MTF. Registration marks make the regions easy to select and (in Imatest 4.0+)work with automatic region detection. A neutral gray background helps ensure that the chart will be well-exposed in auto exposure cameras.

It is supported by Stepchart, Multicharts, and Multitest, and can be used with the Dynamic Range postprocessor if several manual exposures are available.

This chart is produced with a high-precision LVT film recording process for the best possible density range, low noise, and fine detail. Available in the Imatest Store.


QA-62
QA-62 target
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 target
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
R
eflective Material
ST-52ISO-14524
12-patch
OECF target
(circular)
ST-52 target
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. Nominal patch densities are .1, .2, .31, .43, .56, .7, .87, 1.05, 1.27, 1.53, 1.86, 2.30. The inkjet-printed version available at the Imatest Store includes registration marks for automatic region detection in Imatest 4.0+.
  Part No.
ST-52-RM
Overall Size
356mm x 200mm
Material
R
eflective Material

ISO-15739
Noise target

ISO-15739 Noise target
This is a 15-patch grayscale step chart with 12 of the patches in a somewhat elliptical arrangement on the periphery and three in an inside row. Nominal patch densities are 0.1, 0.19, 0.3, 0.41, 0.53, 0.66, 0.81, 0.97, 1.17, 1.39, 1.66, 2.0 for the 12 peripheral patches and 0.77, 0.90, 1.05 for the three central patches. The relatively large patches are especially good for measuring noise. All Stepchart measurements are supported. The inkjet-printed version available at the Imatest Store includes registration marks for automatic region detection in Imatest 4.0+.
Portion of proposed low-contrast ISO 12233 chart20-patch
OECF
targets
(circular)TE241
20-patch OECF chart: portion of proposed low contrast ISO 12233 chart
Several charts use this 20-patch arrangement.(upper) Portion of proposed low-contrast ISO 12233 chartWhen 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

Image Engineering/Esser Test Charts TE 241 chart
ITE Grayscale
ITE Grayscale target
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. Imatest can manufacture one on request. The maximum contrast ratio for both versions is approximately 40:1.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.ITE Grayscale densities (default Imatest reference values)
Gamma = 0.45:
1.70 1.31 1.08 0.87 0.71 0.56 0.43 0.34 0.24 0.15 0.08

Gamma = 1: 1.70 1.00 0.74 0.58 0.46 0.37 0.30 0.23 0.18 0.13 0.08
QA-61
ISO-16067-1
Scanner
QA-61 QA-61 REFLECTIVE SCANNER TEST CHART (ISO-16067-1)
Data: Size 100mm x 152mm (4in x 6in); Designed to ISO-16067-1 specifications. Includes Landolt Ring, alphanumeric resolution and slant edge charts; grey step patches, horizontal, vertical and slanted ronchi patterns (6 – 40 c/mm) plus the APPLIED T-100 Digital Electronic Pixel target.
Notes: Used for determining reflective light resolution & imaging characteristics of digital scanning systems. For full description, see QA-61 Product specifications.

Part No.
QA-61-ISO-16067-1-P-RP
Overall Size
102 x 152mm (4 x 6in)
Material
Reflective Material

Instructions for Special/ISO charts

Run Stepchart, Multicharts, or Multitest by clicking on the appropriate button in the Imatest main window. The example below illustrates Stepchart: the procedures are similar for Multicharts and Multitest.

Select the approximate crop region, which typically includes only the grayscale patches, (Use the registration marks for selecting corners in the 36-patch Dynamic Range chart; ignore any crop or selection marks in other charts.) 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 Special/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) crop
QA-61 ISO-
16067-1 Scanner
QA-62 crop
QA-62
ST-51 (EIA Grayscale) crop
ST-51
EIA Grayscale
ST-52 (ISO-14524) crop
ST-52
ISO-14524
12-patch OECF target
 
ISO-15739 Noise target crop
ISO-15739
Noise target
 
 
20-patch OECF target crop
20-patch OECF
targets
ITE Grayscale target
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.

Stepchart_AI_ISO_select
SFRplus settings window for non-linear charts.
Most settings are described in Using Stepchart.

You can select either Expert or Simplified mode for the settings window. In Simplified mode many settings are grayed out so they can’t be set. If you press Standard settings, commonly used settings (recommended for beginners) are selected.

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.

Fine ROI (crop) adjustment

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. The Distortion slider allows highly distorted (barrel or pincushion) images to be analyzed. Fill factor may have to be reduced in the presence of extreme distortion.

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

The table below shows the patch order for several grayscale targets. Use these orders when creating a custom density file (full instructions on Measuring test chart patches).

Orientation and numbering of patches for monochrome targets
QA-61_patch_numbers
QA-62_patch_numbers
ST51_patch_numbers
ISO-14524_patch_numbers
QA-61 ISO-
16067-1 Scanner
QA-62
ST-51
EIA Grayscale
ST-52 ISO-14524
OECF target
ISO-15739_patch_numbers
OECF-20_patch_numbers
ITE_patch_numbers
DR-36_patch_numbers
SO-15739
Noise target

20-patch
OECF targets
ITE Grayscale
36-Patch Dynamic
Range chart

You can find the patch order for any grayscale or color chart by running Multicharts. For most of the charts on this page, select 7. Special Grayscale Stepcharts. Display 3. Split Colors: Reference/Input and check the Numbers checkbox. This displays the patch numbers, as shown below.

ISO-15739_patch_example
Multicharts result, showing patch numbers