Mamiya 7 65mm Lens: Measuring Front and Rear Group Spacing
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
Inspecting a Mamiya 7 65mm lens for potential focus issues.
All lenses that I service get certain parameters evaluated and on the Mamiya 7 65mm and 43mm lenses, front and rear lens group spacing is important. There is a base spacing of 0.30mm and various spacers (from 0.05mm to 0.30mm) are used. This spacing of the elements is important for optimal image quality.
The first video shows the two measurement fixtures. First thing to do is zero out the dials by placing them on the appropriate gauge base.
Video two shows the front element group being tested and it is -0.01 out. The third video shows the rear element group and it is 0.01 out. To calculate the spacer needed the formula is : 0.30mm + (-0.01 + 0.01) So, all that is needed is the 0.30mm spacer in this lens.
