I have just received a Bosscreen for my Wista 4x5 and have fitted it on the camera without problems. Just one question arises since after mounting it slight newton rings have appeared on the glass. I want to underline that the glass has been mounted properly and no tension is p resent anywhere on the glass. When I checked that the glass was firmly in place by gently pushing on it I heard strange unknown sounds . I lately discovered the weak sounds I was hearing were probably from the wax layer detaching from the o uter glass hence forming very slight newton rings that in any way do not affect the viewing. I want to stress the fact that when I checked the glass to be in p lace I put a pressure so weak and gentle that I can not believe this is not a co mmon phenomenon. Otherwise that means the Bosscreen is a glass more delicate tha n butterfly wings. With this message I am just asking if this experience has occurred also to ther users of this focusing screen. Thanks for reading.