Focus offset after focusing screen replacement

Symptome

A major focus offset appears after replacing the focusing screen, Fresnel, or frame.

Contextes

Often observed right after changing the viewing stack, while the body was consistent before.

Causes a envisager

• Fresnel installed in the wrong orientation
• Non-matching frame
• Focusing screen not seated correctly
• Incorrect height or locating tabs
• Incorrect focusing screen / Fresnel / frame stack

Checks utiles

1. Return to an original or known-good focusing screen.
2. Run another film test on a high-contrast subject.
3. Compare the result under a loupe and then on a scan.
4. Isolate each variable in the viewing stack.

Heuristique

When focus suddenly becomes wrong after a focusing-screen change, suspect the viewing stack first before blaming the camera body.