Fujinion W f5.6 210mm fuzzy at wide open

[pound]

hi guys

I have 2 of these Fujinion W f5.6 210mm. The first one I have been using it for a few years and it focused sharp at infinity at f5.6 on the camera ground glass.
However for the 2nd lens (bought a while back but seldom use it), at f5.6, the image will look fuzzy and will only focused sharp at infinity at f16 or smaller. I swapped the lens elements around the 2 lens and narrowed it down to the 2nd lens front element causing the issue.

Anyone know what is the cause and how can it be fixed?

Thank you!

[Havoc]

A missing shim would be my guess.

[ic-racer]

Lens re-assembled wrong? Sometimes the lens elements don't contact the base of the groove if you don't press them in hard enough. The locking ring will still screw in place over the element and the lens can look like it is re-assembled correctly.

[pound]

thank you all.
I opened the front element and there is a shim. my other lens has a bent filter thread so I could not open to do a comparison.
Otherwise I made sure all the lens elements are sitting correctly. Seems to have nio improvements.

[Bernice Loui]

Sounding like this Fujinon lens is a dud. Time to move it on.
As for shims, they are set and selected during production of a specific lens with the shim thickness specific to each lens.

Example of why web page crowing about the magnificence of any given lens is dependent on the specific individual lens. In most cases, a modern lens is good as purchased, other time they are horrid. This is why testing of a specific individual lens for meeting image making goals is SO important.



Bernice

[Doremus Scudder]

A lot of things could be wrong. If you bought the lens used, it may have a front or rear group that's been swapped out with another lens (even one of a different focal length...). It could have been dropped, remounted in a different shutter without necessary shims, etc.

Also, there may be something in the way preventing the elements from seating correctly in the shutter. I have a Nikkor M 300mm that was a real dog until I discovered that the lens board I had it on was too thick to allow the rear element to seat properly in the shutter. Now it's just great...

Check everything you can. The cause is likely some mechanical misalignment somewhere. I really doubt Fuji would have let a lens that didn't focus wide open pass their QC.

Best,

Doremus

[Bernice Loui]

Odd of Fujinon shipping a defective lens when new, vanishingly small. Stuff that had happened to this lens between it's original owner-user to it's most recent owner_most anything is possible.

Or why testing any used lens before accepting is a really good idea. To do this properly demands some knowledge and expectations of what any LF lens should and could be and knowing how any given lens could meet the image maker's print goals. This is the difficult part.



Bernice

[Louis Pacilla]

The OP may want to post photos of both front & back of Fujinon lens in question as well as couple of side views. This will help us to check if something is physically out of order. Like mismatched cells?

[Bob Salomon]

The OP may want to post photos of both front & back of Fujinon lens in question as well as couple of side views. This will help us to check if something is physically out of order. Like mismatched cells?

Maybe he should post a picture of the damage to the front of the lens. That impact damage is probably related to the problem.

[Louis Pacilla]

Maybe he should post a picture of the damage to the front of the lens. That impact damage is probably related to the problem.

I missed the damage part but YES post a picture of the damage for sure.