What is 90 280mm on aps c in full frame?

90-280mm on APS-C gives the view of 135-420mm on full frame.

The same view on every common format:

• Medium format (44 x 33): 171-532mm
• Full frame: 135-420mm
• APS-C (yours): 90-280mm
• APS-C (Canon): 84-262mm
• Micro Four Thirds: 68-210mm
• 1-inch: 50-156mm
• 1/1.3-inch: 38-117mm
• 1/1.7-inch: 29-91mm
• 1/2.3-inch: 24-75mm

Crop factors are by the sensor diagonal, rounded as they're usually quoted; a format with a different shape (4:3 against 3:2) frames a little differently across the width. More in the focal length converter.

Computed from the sensor sizes, not written by a model.