Assess print unevenness objectively using only a standard flatbed scanner. Three ISO/IEC 24790 measures — mottling, graininess and banding — from scanned images in one pass, with results that correlate well with visual quality evaluation.
PapEye Print Uniformity is user-friendly software designed to help paper, board and print professionals assess print unevenness based on algorithms from the ISO/IEC 24790 standard. Using a standard scanner, you can quickly analyse samples and gain objective insights into your print quality.
The application is based on computational image analysis of scanned samples. It provides objective evaluation of mottling and similar marbling effects, the fine graininess of a printed area, and banding — the periodic striping that printing mechanics leave across a sheet.
Each measure is reported as a single number describing the perceived visual evenness of the printed sample.
The software is a standalone executable and licenses are sold as a permanent license for a single PC. List of recommended scanners is available from Tapio Measurement Technologies.
Unevenness is not one defect. Print uniformity needs to be evaluated at different scales because the human eye responds differently to each type of variation.
Earlier PapEye versions measured mottling and graininess as separate products. They are now combined in PapEye Print Uniformity, together with banding. Draw the analysis regions to produce every measurement for the supported region size and scan resolution.
| Measure | What it detects | Typical causes | Minimum region | Scanner resolution |
|---|---|---|---|---|
| Mottling | Blotching a few millimetres across | Absorption differences, coating variation and back-trap mottle | 25.4 × 25.4 mm | 300 DPI |
| Graininess | Fine texture below approximately one millimetre | Screening, ink-film break-up and base-sheet formation | 12.7 × 12.7 mm | 1200 DPI |
| Banding | Stripes running across the printed sheet | Drum, roller and feed-step periodicity in the press or printer | 150 mm across × 100 mm down | 600 DPI |
If the selected region or scan resolution does not meet a measurement’s requirements, PapEye displays a dash instead of reporting an unreliable value.
Example of bad quality marbled print.
Mottling score 1.79
Example of good print quality.
Mottling score 0.40
The human eye recognises mottling effects with different sensitivities, depending on the size of the defect. With flaw sizes of lower wavelengths, the human eye is relatively insensitive, because it can hardly detect such fine variations. However, the human eye is very sensitive to patch sizes within a certain visible range. PapEye Print Uniformity provides results that correspond well with human perceived print quality.
PapEye Print Uniformity includes scanner reflectance calibration using the scanner’s opto-electronic conversion function, or OECF. A greyscale target containing patches with known reflectance values is needed to create a calibration. PapEye fits a response curve for each colour channel and measures subsequent scans using that calibration.
Calibration is not required for repeatable comparative measurements made using the same scanner and settings. Without calibration, PapEye assumes a default response. With calibration, measurements are calculated using the scanner’s measured response curve, improving comparability between different scanners and laboratories.
A calibration can be exported and transferred to another PapEye installation. Calibrations are stored according to scanner name, allowing a laboratory with several instruments to maintain a separate calibration for each scanner.
| Operating system | Windows |
| Application | Standalone executable with no conventional installation required |
| Licensing | Permanent license for PapEye Print Uniformity on a single PC |
| Input formats | PNG, JPEG, GIF, BMP, TIFF and PDF |
| Result exports | CSV and Excel-compatible exports, result thumbnails and sample-region files |
| Batch processing | Analysis and export of entire folders containing similar samples |
| Command line | Available for automated and scripted analysis |
Licenses are issued per PapEye product and per machine. A license for one PapEye product does not unlock another product.
Old Mottling and Graininess licences do not automatically unlock Print Uniformity.
On first run, PapEye displays a Machine ID. Send the Machine ID to Tapio Measurement Technologies and place the returned license file in the .papeye folder in the home directory of the user.
The difference is the scale of the variation being measured.
Both measurements filter the scanned region to a selected band of spatial frequencies, trim the margins, divide the remaining area into tiles and calculate a result from the variation inside those tiles.
Graininess measures fine detail below approximately one millimetre. Mottling measures larger blotching several millimetres across. The ISO/IEC 24790 standard defines separate analysis scales for the two measurements.
Banding requires a nominally uniform area of at least 150 mm across and 100 mm down, scanned at 600 DPI or higher.
Sometimes patch samples are not large enough to meet this requirement. Scan a larger uniform printed area to receive a banding result.
Graininess measures fine spatial variation reaching approximately 1.5 cycles per millimetre.
Attempting to measure this from a lower-resolution scan would measure image resampling effects rather than the printed sheet. PapEye therefore requires a 1200 DPI scan for graininess.
For mottling and graininess, the region must meet the minimum size in both directions, but it does not have to be perfectly square. The software calculates the average value within the selected rectangular region.
For banding, the two directions are not interchangeable. The profile runs horizontally across the sheet and is averaged vertically down it. Therefore, the 150 mm minimum dimension must be horizontal.
Yes. Open Settings → Show results and select which of the three measurements should appear in the results table.
All three measurements are still analysed when their resolution and region-size requirements are met, and all available results are included in exports. This setting only controls which result columns are displayed on screen.
Use 1200 DPI when you want all three measurements.
The ISO/IEC 24790 measurement conditions specify 1200 DPI, and this is the resolution required for graininess. Mottling and banding can be analysed from suitable lower-resolution scans.
Our tests have shown that mottling analysis produces equivalent results with 300 DPI scans from the same samples.
Calibration is not essential for repeatable comparisons made with the same scanner, but it is recommended. PapEye includes features for calibrating the scanner response.
Without calibration, PapEye assumes an sRGB response. With calibration, measurements are made through the scanner’s measured response curve, improving comparability between different instruments.
Higher values indicate more visible unevenness.
The measurements use spatial filtering and tile-based variation analysis to emphasise the spatial frequencies to which the human eye is most sensitive.
In practice, the ranking of samples corresponds well with visual ranking. Absolute values should be compared using a consistent scanner, resolution, calibration and sample-placement procedure.
Yes. Batch processing analyses every suitable image in a folder using the same sample-region definitions.
The results for an entire folder can be exported to CSV files for comparison between production runs, suppliers and sample groups.
Evaluate mottling, graininess and banding from standard flatbed scanner images using one straightforward Windows application. Contact Tapio Measurement Technologies to request a demonstration, discuss your measurement needs or receive a quote.