Does anyone have experience using this lens on this format? The Cameraeccentric resource (1949 brochure) doesn't say what the useful image circle is, though it is recommended for 8X10. It is also recommended for a 7X17 banquet format, which would be an 18.3" (464mm) diagonal. The closest protar would be a 23/18 combination, which is recommended for 11X14 when stopped down. Thanks.