Image forming apparatus for forming-adjustment image on sheet

An image forming apparatus comprising:

• an image forming unit configured to form an image on a sheet based on an image forming condition;
• a conveyance unit configured to convey a sheet having a pattern image formed thereon by the image forming unit to a conveyance path, the pattern image including a plurality of patch images and a trigger image used for controlling a reading timing for each of the plurality of patch images;
• a reading unit configured to read the pattern image on the sheet while the sheet having the pattern image formed thereon is conveyed by the conveyance unit;
• and
• a controller configured to:
• in a case of forming the pattern image on a first sheet having a first basis weight, control the image forming unit to form a first pattern image on the first sheet, and generate the image forming condition based on a result of reading the first pattern image by the reading unit;
• in a case of forming the pattern image on a second sheet having the same size as a size of the first sheet and having a second basis weight larger than the first basis weight, control the image forming unit to form a second pattern image on the second sheet, and generate the image forming condition based on a result of reading the second pattern image by the reading unit;
• the number of trigger images included in the second pattern image being larger than the number of trigger images included in the first pattern image, a position of one trigger image on the second sheet being different from a position of another trigger image on the second sheet in a conveyance direction in which the sheet is conveyed.