X-Y Addressability Indicator and Gradient - how to use this scale

[MannyV]

Hi all,
Need some education here please.
The circular part seem fairly straight forward to read and understand. How do I read and test this step wedge scale portion horizontally and vertically for test? SPI - Samples per inch?

 

[SteveSuffRIT]

Franz Sigg from RIT (retired, Switzerland) developed this test target.
I think after you output the file on a device, a moire pattern appears in the patch that matches the spi addressability.

 

[Ulrich]

SPI: Spots per Inch

following Steves moire pattern indicating: like this in the top half at 300 (but here it is just a screenshot..., we all know it from a film strip to identify the lpi of a print...):

 

[MannyV]

Thank you, very practical device to measure vendors addressability when shopping around. Reading about vendors capabilities and proving it are always more reassuring when shopping. This can a good start also for identifying root causes.

I pulled this from one of his RIT papers
Addressability Indicator. Sometimes output devices indicate a higher addressability than they mechanically produce. This target helps to determine true mechanical addressability.