I have been lucky avoiding Fungi in most of my lenses bar one - my SMC A50/1.7 . It had an annoying flourish just off-center that I'm sure did nothing to effect IQ, but sure drove me bananas and would send my OCD into overdrive. It was located on the rear of the Front Group, so it could potentially spread to the rear group as well.



I've read up on the net, and did find some other pics and guides to the M50/1.7 - but this is unfortunately slightly different in assembly of the front group which meant that it was helpful - but not the answer. I umm'ed and arrr'ed about it, posted a thread here asking for suggestions, fashioned myself a crude Spanner Wrench suitable for the front group.. and eventually decided to give it a go

So armed with having read up on a number of other peoples experiences, and having studied http://www.pentax-manuals.com/manuals/service/smca5017.pdf I set about cleaning it.

DISCLAIMER: I have no idea what I'm doing. No really - First lens I've ever pulled apart and cleaned. I read lots of other lens type cleaning guides, and studied the exploded Pentax Service Diagram carefully. Please do not consider this an intelligent or well thought out 'how-to' guide - its simply what *I* did to clean my lens that I offer up as I could not find anything specific relating to Front Groups on A50/1.7 - only rear aperture repair. Repeat my stupidity entirely at your OWN risk!

Here is the tools I presumed I would need all laid out:


Isopropyl Alcohol, for cleaning the Fungus Off and misc cleaning;
Optical Cleaner, for final Lens Clean
Lint Free Lens Cloth
Torch for Inspection
Set of precision screwdrivers, including JIS bits
Tweezers
38mm Rubber Plug with Center Removed
Home Made Spanner Wrench suitable for front group

Set the lens to infinity to make it as short as possible. I then used the "rubber plug" trick to remove the front bezel from the A50/1.7. This is simply a 38mm Basin Plug with the center ring removed. Grip the base, and apply a firm downward pressure on the outside of the plug while twisting counter clockwise - it should spin right out with little trouble.






After removing the bezel, you should now see 3 #0 JIS screws. Remove these and you can lift up and remove the metal filter ring.







You can now see the retaining ring used to hold the front group in place. Once again it is fastened using 3 #0 JIS screws. Carefully remove the screws and set them aside.




If you gently tip up the lens into your palm the front group should now just fall out. Set the rest of the lens body aside and perhaps replace the lens cap to at least stop too many dust mites collecting in there whilst all apart Yes we will of course clean it before reassembly - but why make more work ?

Here is the front group with its retaining ring on top set down next to the lens body.




Now - anyone who has proper tools for the job (I'd highly recommend them ) - LOOK AWAY NOW!!! For any other heavy handy gits like myself - behold my home made Spanner Wrench suitably sized for the front retaining ring of the group:




Grip the base of the group, and with the wrench engaged in the notches whilst pushing down firmly simply rotate counter-clockwise and it should come loose. After I got it untorqued, I just spun it off with my finger tips.




This will free the first lens element, which you can tip over carefully into your hand and set aside. Remember which way it goes - but thankfully on this lens its pretty easy because all the front elements are concave and go with the dome outwards. The middle element will also come free, or you may need to gently lift out the spacer located immediately underneath the first lens element.




You should now be left with the the elements from the front group ready for cleaning and also now have easy access to the front side of the 4th element (not shown, but inside the Base behind the aperture blades. Set it to 1.7 manually to access them ).




Simply clean them and carefully polish them. There is some varied suggestions to removing the fungus - some suggest using Cold Creme and then letting it harden for an hour before removing with Zippo Fluid or Isopropyl Alcohol. I didn't have any Cold Creme available and it seemed to be removed very easily with just good strong Isopropyl Alcohol.




With all the elements cleaned with alcohol, I then used Optical Fluid to clean them all once again and polished them. Using a rocket blower I also blew the lens body out and reassembled the group polishing them each time. Then its simply a matter of reversing the above process to get it all back together ship shape.

Here is the cleaned lens - I think you can tell its clean and Fungi Free I hope..





And here is a shot taken through the 50mm that also serves as a quick Strobist Setup shot (Basic cross light, One softbox, One bare for Rim light) Focus was off a bit sorry - but its mostly sharp

[adr1an]

Oh - a follow up - if you happen to have fungus on the rear elements, then its pretty trivial to remove the rear group, just refer to the Pentax Exploded diagram above.

The password is "Pentax" for the PDF - I didn't set it I've simply passed the link on

[Skog]

Nice

[adr1an]

Nice

Cheers. I don't feel sooo scared about Manual Lenses anymore either...

[nms_photog]

Set the lens to infinity to make it as short as possible. I then used the "rubber plug" trick to remove the front bezel from the A50/1.7. This is simply a 38mm Basin Plug with the center ring removed. Grip the base, and apply a firm downward pressure on the outside of the plug while twisting counter clockwise - it should spin right out with little trouble.

What if this trick doesn't work? "should spin right off with little trouble" is not happening!!! No amount of force is getting this thing off!!!

[nms_photog]

Set the lens to infinity to make it as short as possible. I then used the "rubber plug" trick to remove the front bezel from the A50/1.7. This is simply a 38mm Basin Plug with the center ring removed. Grip the base, and apply a firm downward pressure on the outside of the plug while twisting counter clockwise - it should spin right out with little trouble.

What if this trick doesn't work????? This trim ring is NOT!!! coming off regardless of how much pressure I apply!!! Have darn near wore out a rubber stopper and cut a cople knuckles already!!!

Please help before I throw this thing against a wall!!!!!!!

[adr1an]

What if this trick doesn't work????? This trim ring is NOT!!! coming off regardless of how much pressure I apply!!!

That must be annoying! Make sure you are only gripping the outer ring of the face - hence why I used mine upside down as I did. Used the other way around it also grips the Lens Element Retaining Ring (the one thats notched for the spanner) and wouldn't turn...
On the handful of A and M lenses I have, all of their faces spin off with ease this way. I can only suggest maybe someones been there before you, and crossed the threads or something ?

Tried applying a mild bit of heat to the metal Filter Ring ? this might cause it to expand enough if its cross threaded... Not hit it with a blow torch - just maybe a hair drier on the outside of the body ?

[nms_photog]

That must be annoying! Make sure you are only gripping the outer ring of the face - hence why I used mine upside down as I did. Used the other way around it also grips the Lens Element Retaining Ring (the one thats notched for the spanner) and wouldn't turn...
On the handful of A and M lenses I have, all of their faces spin off with ease this way. I can only suggest maybe someones been there before you, and crossed the threads or something ?

Tried applying a mild bit of heat to the metal Filter Ring ? this might cause it to expand enough if its cross threaded... Not hit it with a blow torch - just maybe a hair drier on the outside of the body ?

Annoying is putting it very mildly!!!! Doesn't look as though this thing has ever been tampered with, and everything I've tried has failed to this point..........seriously about to throw it against a brick wall!!!

This is an 28mm f2.8 KA...........just in case that has something to do with it.............but the front lens looks identical in construction.

[adr1an]

Well ; you could send it to Eric over at Home .
Its a fantastic lens...

Perhaps someone else can offer some advice - I just studied the diagram and bluffed my way through it... hopefully a more experienced person can post some suggestions.

[nms_photog]

Anyone have an idea about how much he charges for cleaning service???

[atupdate]

Anyone have an idea about how much he charges for cleaning service???

Send him an email and he will provide an estimate. His email is on his home page.

Eric's Home Page

Tim

[nms_photog]

Yeh, thanks.........I did, and it's on the way to him now!!!

[adr1an]

Yeh, thanks.........I did, and it's on the way to him now!!!

Great to hear it. Being a minimum of 7500 miles from Eric - it just wouldn't have made sense for me to do it that way - hence my own home job...

[gordon_l34]

Hi,

I realise that this is a late post, but here are the contact details that I use for a camera technichian that I use here in Brisbane. It is F16 Camera service, F16 Camera Service, e-mail info@f16cameraservice.com.au His phone number is 07 3284 1588. He works from home so you can contact him after hours. He does mail order repairs as well.

Regards.

[arnold]

What if this trick doesn't work????? This trim ring is NOT!!! coming off regardless of how much pressure I apply!!! Have darn near wore out a rubber stopper and cut a cople knuckles already!!!

Please help before I throw this thing against a wall!!!!!!!

One time I used a small bottle/jar with the right diameter opening to fit over the ring. You can try using electrical tape over the mouth-edge of the bottle for grip, or for really stubborn rings, use carefully placed double sided tape there. Use paper over the area you don't want to stick. Careful, because I had difficulty getting the ring off the tape once it was removed.