Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!

SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Adaptall diaphragm
View previous topic :: View next topic  


PostPosted: Sat May 08, 2021 1:32 am    Post subject: Adaptall diaphragm Reply with quote

I bought a nice Adaptall 90mm macro 52bb. Whatever the adapter the diaphragm is somewhat lazy and would not close completely unless you play a little bit with the actuator.
Is there a way to restore proper function without dismantling everything which might be out of my reach.


PostPosted: Sat May 08, 2021 4:25 am    Post subject: Reply with quote

Inspect your lens's aperture iris blades for any oily residue. This is usually what causes sluggish aperture operation. If the blades show an oily residue, the only option is to open the lens up and clean the iris blades. Granted, this might be something you won't want to do yourself, in which case you should seek professional service.

It's worth noting that, given the used market value of the SP Adaptall-2 90mm macro, it might not be economic to have the service done. Ultimately it would be your call.


PostPosted: Sat May 08, 2021 9:42 am    Post subject: Reply with quote

The blades are fine. No oil.


PostPosted: Sat May 08, 2021 12:36 pm    Post subject: Reply with quote

This seems to be a not uncommon problem with this lens, I have encountered a couple of examples, and I mention it in the lens description on pentax forums. One possible solution is to tweak the iris return spring position. There used to be a descriptive web page here:

http://www.wiratama.net/camera/category/adaptall2a93b47ccbf

But now getting a 404...

In a nutshell, remove the mount, remove the rear optical group and mounting. There is a spring that is fixed by a blob of thread locker type stuff, this needs to be relaxed slightly. Found these pics, which I think were off that site...

My own efforts, one seemed to fix, the other only partially. I have an impresion that the iris mechanics are delicately balanced, so that a bit of dirt or something making the baldes just a touch sticky has this effect.

#1


#2


#3


#4


PostPosted: Sat May 08, 2021 4:14 pm    Post subject: Reply with quote

The original article is there - just use Wayback Machine

https://web.archive.org/web/20210122222349/http://www.wiratama.net/camera/category/adaptall2a93b47ccbf


PostPosted: Sat May 08, 2021 5:50 pm    Post subject: Reply with quote

Fantastic information, maybe out of my technical reach.