Ive always heard that the later Dynar-type Heliars had a 60 degree image circle, while the earlier pre-WW1 Heliars only had a 50 degree image circle. Today I had the opportunity to do a little testing, so I installed my Dynar-type Heliar on a 7x17 camera and did some measurements. At infinity focus and all movements centered, it will easily cover the 167mm x 424mm ground glass. I dont lose the circle of illumination until I shift the back about 60mm to the side, which computes to a circle of about 544mm, or over 65 degrees.