Focus error with Bronica S2? The problem is not in the screen!

When the foam under the mirror disintegrates, the mirror drops down until it rests on the raised metal bosses on its support plate - about 1/2mm below its correct position. The resulting error at the screen can be more than 1mm. This can be hard to spot clearly on the Bronica focusing screen, since the screen has no focus aid and the direction of the error is such that the screen never quite gets sharp at the infinity stop on a distant target .... you never see it get fully sharp and then off again as you would if the error was in the other direction.

 

If you have this problem with a Bronica S2 or S2A, the answer is to replace the foam under the mirror. But it's not an impossible DIY job:. you only have to remove the 2 screws at the front corners of the mirror, the rear ones can stay in place as you hinge the frame upwards.... and since these 2 screws can be reached through the lens mount, you do not have to remove the screen for access to replace the mirror foam.

Done