1. An image formation apparatus which has a function to make processing speed for image formation changeable, comprising: image formation means for forming an image on an image support body; density measurement means for measuring a density of the image formed by said image formation means; and control means for causing said image formation means to form plural images for measurement at first processing speed, causing said density measurement means to measure densities of the formed images for measurement, determining an image formation condition at said first processing speed on the basis of the densities measured by said density measurement means, and stores the determined image formation condition in a memory, wherein said control means determines the image formation condition at second processing speed different from said first processing speed, by correcting the image formation condition at said first processing speed stored in said memory.