Frequently Asked Questions

Question #1 - Why would I see differences in the results if I run a test target image on ImageZebra, and another tool such as Delt.ae?

Answer #1:

Performing an item-to-item comparison is an ill-posed question, for the following reasons:

  • The name of the metrics is not consistent between the two tools. ImageZebra is using terminology as defined by FADGI.

  • Delt.ae does not test and report all the FADGI metrics available on the Golden Thread test pattern. Below is a list of the missing metrics not available with Delt.ae:

    • OECF (Tone Response) - not measured in either colorimetric (L*) or digital counts
  • White Balance Error - not measured in either colorimetric (L*) or digital counts
  • Resolution - FADGI guidelines have established resolution limits with star ratings. Delt.ae measures the resolution but does not report the star rating

  • Some metrics are only partially implemented on Delt.ae

    • Noise (digital counts) - Noise measurement in units of digital counts is not available, however the Noise measurement in colorimetric units (delta L* Stdev) is available
  • Reproduction Scale Accuracy – Delt.ae measures the actual resolution of the scanned image, however, it does not summarize the FADGI star rating for this measurement. The summary report can be misleading when the metric is not assigned a star rating and reported with the other metrics.

  • Delt.ae uses the average SFR response of the 5 locations to determine the FADGI star rating. The Image Zebra and Golden Thread summary reports the worst star rating from all locations. The average location (as done by Delt.ae) could be misleading, and is not sufficiently diagnostic.

  • There is also a concern about the size of the analysis region used by Delt.ae, as well as differences in location where the two tools make their exact measurements. It is possible the small ROI could be giving inaccurate results.

  • Color Accuracy: Image Zebra currently uses the worst color patch for the summary star rating. However, this will change in the next release to be consistent with Delt.ae and Golden Thread software, which computes the Average dE color error of all color and neutral patches before determination of the star rating.

  • Image Zebra does not currently measure the color to color misregistration. It is unclear whether Delt.ae is using the very small ROI’s which it displays on the image. If so, there could be a large error source in the accuracy of the color registration metric. It appears Delt.ae is reporting the average color misregistration in the summary.

  • Delt.ae is no longer actively supported and no longer participates in any ISO standards.