Gio. Francesco Barbieri, surnamed Guercino da Cento, would, to speak with precision, be better ranked among the artists of Ferrara, to which city Cento is subject; but we must observe the almost universal custom of including him among the Caracci's disciples. This has arisen either from a tradition that his genius at an early age received some bias towards design from the Caracci, which but ill accords with the epoch of his age, or from the circumstance of his having taken one of Lodovico's pictures for a model, which is slight ground enough for attaching him to the school. Moreover, he never frequented the Caracci's academy; but, after staying a short time with Cremonini, his fellow-countryman, at Bologna, he returned to Cento, and there resided with Benedetto Gennari the elder, first as his pupil, next his colleague, and lastly his kinsman. Some too would contend that one among the masters of Gio. Francesco was Gio. Batista Gennari, who in 1606 painted for S. Biagio, in Bologna, a Madonna among various saints, in a style resembling Procaccini. And indeed the Paradise, at S. Spirito in Cento, and an altar-piece at the Capuccini, with other early works by Guercino, partake of the old style. Subsequently he studied, along with Benedetto, to find by experiment what constituted grand effect in the art, in which taste I cannot distinguish, with the generality of dilettanti and writers, two manners only; he having openly professed three, as we learn from Sig. Righetti, in his Description of the paintings of Cento.
Of these the first is the least known, consisting of abundance of strong shades, with sufficiently animated lights, less studied in the features and in the extremities, with fleshes inclining to the yellow; in the rest less attractive in point of colouring; a manner distantly resembling that of Caravaggio, in which kind are to be found several specimens both at Cento and in S. Guglielmo a' ministri degl'Infermi at Bologna. From this he passed to his second manner, which is by far the most pleasing and valuable. He continued to improve it during several years, with the aid of other schools; in this interval often visiting Bologna, residing for some time at Venice, and remaining many years at Rome along with the most eminent followers of Caracci, and entering into terms of friendship with Caravaggio. His taste is mainly founded on the style of this last master; displaying strong contrast of light and shadow; both exceedingly bold, yet mingled with much sweetness and harmony, and with powerful art of relief, a branch so greatly admired by professors.[39] Hence some foreigners have bestowed on him the title of the magician of Italian painting; for in him were renewed those celebrated illusions of antiquity, such as that of the boy who stretched forth his hand to snatch the painted fruit. From Caravaggio too he borrowed the custom of obscuring his outlines, and availed himself of it for despatch. He also imitated his half-sized figures upon one ground, and for the most part composed his historical pictures in this method. Yet he studied to become more correct in point of design, and more select than Caravaggio; not that he ever attained peculiar elegance or peculiar dignity of features, though most frequently he drew his heads, like a sound observer of nature, with graceful turns, easy natural attitudes, and a colouring, which if not the most delicate, is at least the most sound and most juicy. Often in comparing the figures of Guido with Guercino's, one would say that the former had been fed with roses, as observed by one of the ancients, and the latter with flesh. How far he excelled as a colourist in his draperies, formed in the taste of the best Venetians, in his landscape, and in his accessories, will sufficiently appear on beholding his S. Petronilla in the Quirinal, or his picture of Christ risen from the Dead, at Cento,[40] or his St. Helen, at the Mendicants in Venice; excellent specimens of his second manner. To the same belong in general all that he left at Rome, even his greater works, such as the S. Gio. Grisogono in the soffitto of that church, or the Aurora, adorning the villa Lodovisi. Yet he surpassed even these, to the surprise of all, in the cupola of the Piacenza cathedral; and in the same city he appears to have competed with Pordenone, and in point of vigour of style to have gone beyond him.