Franz Wilhelm Seiwert’s 'Wandbild für einen Fotografen' – estimate €400,000-600,000 at Grisebach on June 10.

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He was also a prolific collector of works by the numerous artists he knew in Cologne and the surrounding area.

On June 10, Grisebach in Berlin is selling paintings from Sander’s collection which have not been on the market since he acquired them in the 1920s.

One of the highlights is Franz Wilhelm Seiwert’s Wandbild für einen Fotografen (Wall Painting for a Photographer), a 3ft 7in x 5ft 1in (1.1 x 1.55m) canvas, painted for Sander in 1925, which incorporates the depiction of a plate camera with bellows and the inverted view of a person on the right of the composition. The small central figure in a white circle of light is also shown as seen through the lens of a camera.

For many decades, the wall painting had pride of place in Sander’s Cologne house. The guide now is €400,000-600,000.