Mamiya 65/4 K/L lens

[MEB]

I am using the Mamiya 65/4 K/L lens on my Mamiya RZ 67 Pro camera successfully. The only thing I am surprised about is the blurriness equally in all corners even at f/5.6-8. Is this normal for this lens? I didn't test it fully so far, but is a much smaller aperture required to get better corner-to-corner sharpness? I am aware that there is a newer RZ lens version available, but I doubt that this is a malfunction of the specific K/L lens version.

 

[choiliefan]

I have a large format lens which does the same thing. The rear lens group is a mismatched kluge to the front group and shutter. Bought it through ebay and by the time I tested it, it was too late to return. Hope this isn't the case with yours.

 

[mweintraub]

Is this one of the floating element models?

 

[shutterfinger]

65mm f4 lens diagram from http://www.cameramanuals.org/mamiya_pdf/mamiya_rz67_interchangeable_lenses.pdf
No lens should produce images like that. Element(s) reversed, incorrect order, incorrect element, missing element, incorrect spacing.

 

[MEB]

View attachment 205430
65mm f4 lens diagram from http://www.cameramanuals.org/mamiya_pdf/mamiya_rz67_interchangeable_lenses.pdf
No lens should produce images like that. Element(s) reversed, incorrect order, incorrect element, missing element, incorrect spacing.

The metal ring fixing the rear lens has two marks and looks like somebody has opened it, but the lens itself looks perfectly fine. Also the rear lens arrangement rotated - I just fixed it more tightly by screwing it clockwise with my Copal lens based wrench tool. Now it sits tight - I checked with the magnification glass in the viewfinder and the depth of field preview, the corners seem to be sharp now with the aperture closed a bit. The element was likely loose from the beginning after I purchased the lens and never realized it until it got worse.

 

[shutterfinger]

Unscrew the rear lens group from the main barrel. In the diagram the 3 inner elements are likely cemented and are possibly reversed. Verify correct assembly order and reassemble. The outer most element will be the most difficult to determine orientation as both side are very similar.
Post pictures of the lens rear group if confusion rules.

 

[MEB]

Unscrew the rear lens group from the main barrel. In the diagram the 3 inner elements are likely cemented and are possibly reversed. Verify correct assembly order and reassemble. The outer most element will be the most difficult to determine orientation as both side are very similar.
Post pictures of the lens rear group if confusion rules.

Thanks - I will keep this in mind as next option in case the problem remains. So far it looks really good now in the viewfinder in the corners after I tightened the loose rear lens group barrel. This was a new encounter for me!

 

[shutterfinger]

Retainers are made to fit with the elements in one orientation only. Reversed elements will prevent the retainer from seating properly resulting in incorrect spacing of the group even though the retainer will snug/tighten. Loose retainer=incorrect spacing.

 

[MEB]

Quick update: I can now with certainty confirm that the rear lens group was loose and just had to be fully tightened. I took 10 exposures with an older B&W film at different aperture stops, and now I have excellent corner-to-corner sharpness. Thanks for all the help!

 

[WilmarcoImaging]

Good news MEB and thanks for closing the loop.