Base documentaire Nicos Mamiya's doc
Attention atelier: verifier environnement propre, eclairage stable et protection des surfaces sensibles avant intervention.
Prudence : ouvrir un boîtier ancien peut l'abîmer définitivement. Si l'appareil a une forte valeur sentimentale ou financière, passer par un réparateur compétent reste souvent le meilleur choix.
Procedure

Focus and viewfinder check

Focus and viewfinder check procedure for Mamiya camera bodies.

Objectif

Check whether an apparent focus problem comes from the body, the focusing screen, or the focusing screen / Fresnel / frame assembly.

Prerequis

  • Tripod
  • High-contrast subject
  • Full aperture
  • Same focusing reference for every frame
  • Ability to defocus between each shot

Etapes

  1. Run a test with an original focusing screen or a known-good assembly.
  2. Defocus between each frame.
  3. Compare finder focus and film result on a high-contrast subject.
  4. Check the negative with a loupe and then, if useful, on a scan.
  5. If a major offset appears after a focusing-screen change, isolate the viewing stack variable first.

Vigilance

  • Abnormal halos or reflections
  • Fresnel possibly in the wrong orientation
  • Suspicious frame seating or height
  • Wrong result only with a specific focusing screen or frame

Validation

Do not blame the camera body until an original or known-good focusing screen has served as the reference.

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