1. A wet-type image formation apparatus comprising: an image carrier carrying an electrostatic latent image; a developer carrier conveying liquid developer to a developing portion, which is a position opposite to said image carrier, and developing said electrostatic latent image to form a toner image; a detecting unit detecting an image density of said toner image; and a control unit adjusting, based on said image density detected by said detecting unit, conveyance amount and charge amount of toner in said liquid developer conveyed to said developing portion by said developer carrier, when setting a standard image formation condition for performing normal image formation, said control unit adjusting both said conveyance amount and said charge amount such that an image density of said toner image becomes constant even when a contrast potential is increased to be equal to or more than a predetermined standard contrast potential and such that a developing characteristic is obtained in which the image density of the toner image having become constant falls in a target density range, and setting a condition attained at a time of completion of the adjustments as said standard image formation condition, during the normal image formation, said control unit obtaining an image density of a patch image formed at a high contrast potential higher than said standard contrast potential and an image density of a patch image formed at a low contrast potential lower than said standard contrast potential, said control unit adjusting said conveyance amount when the image density of the patch image formed at said high contrast potential is varied from the developing characteristic for said standard image formation condition, said control unit adjusting said charge amount when the image density of the patch image formed at said low contrast potential is varied from the developing characteristic for said standard image formation condition.