Ejection amount upper limit value determination method and printing device

An ejection amount upper limit value determination method for determining, with respect to a liquid ejected from a print head to a medium, an upper limit value of a per unit area ejection amount with allowable liquid bleeding,

• the liquid including a plurality of different color types,
• the ejection amount upper limit value determination method comprising:
• a test pattern formation step of forming, on the medium, a test pattern including a plurality of pattern arrays, the pattern arrays including a plurality of patches having different ejection amounts and each patch including a bleeding detection region and a background region having a color different from that of the bleeding detection region and
• an upper limit value determination step of acquiring reading results of the plurality of patches included in the pattern arrays and determining the upper limit value based on the reading results of the plurality of patches, wherein
• in the upper limit value determination step,
• a provisional ejection amount upper limit value, which is a provisional value of the upper limit value, is determined for each of the pattern arrays based on reading results of the plurality of patches included in the pattern arrays,
• when a difference between a maximum value of the plurality of the provisional ejection amount upper limit values obtained for the plurality of pattern arrays and a minimum value of the plurality of the provisional ejection amount upper limit values is within an allowable range, one of the minimum value and the maximum value is determined as the upper limit value, and
• when the difference exceeds the allowable range, the upper limit value is determined to be greater than the minimum value and also less than the maximum value.