I own a Porst 650 XL and Porst 1500 XL Microcomputer and was wondering about the the precision of the split viewfinders on each of them. I read the instructions which instruct me to zoom in all the was, focus zoomed in, the zoom out to a desired wider angle. When I zoom in to focus, the split finder lines up, but the split finder lines do not stay aligned upon zooming out and I guess I thought the lens should be parafocal upon zooming. Does this mean my split viewfinder is not accurate? Any guidance is appreciated.