Stopping light leaks in lens adapter?

[Doug A]

I'm using a full frame Pentax K-1 full spectrum DSLR. Most of my lenses are M42 screw mount. This is easy to work with since the Pentax PK bayonet allows flush mounting one style of the M42 adapter inside. This adapter style doesn't change infinity focus. But, to remove the lens, it has to be removed by unscrewing the lens. 

 

The second style adapter has about about 1/2 mm extension. This allows the lens to be removed via bayonet. Problem is light leaks. There is about a 2 x 5mm slot cut into the adapter flange it leaks like crazy. To use the EL-Nikkor 80 a very thin black plastic piece was was wedged in. Now I have to remove this all the time to add a Petri M42 teleconverter. 

 

I think the best fix would be to use glue or putty to fill this slot in. Any ideas? Sorry for the long post.

Thanks,

Doug A

[dabateman]

I don't think this is a long post.

Can you show an image of the problem hole?

Can you get some sticky black flocking material and use that to block the hole.

Otherwise J-B weld black epoxy might work. I have used that before and its ok to block light.

[Doug A]

@dabateman I copied this from a website.  Hope it works. Applying flocking won't work long term because this part of the adapter is sandwiched between the camera mount and rear of lens. The rotation of constant lens changing will "wipe off" anything on either side of the adapter. I managed with the EL-Nikkor because the adapter was never removed. To use the Petri 2x converter the adapter has to be moved. Best hope seems to be filling in the slot flush with both sides of the adapter. If JB Weld is used, what can the adapter sit on so the glue won't stick to it?

 

Thanks,

Doug A

[Andrea B.]

saran wrap ???

 

So the base of the lens does not cover that slot??

[dabateman]

If you want to fill it with glue, I would use tape on one side to create a base, then fill in.

After, remove the tape.

 

Best if you use sticky flocking material with flocking material facingiout and sticky side facing the hole. Just incase after the addition of the epoxy,  you can't remove the tape or sticky flocking material. 

 

[Doug A]

@Andrea B. It depends on the lens in use. The larger ones do cover most of the slot. On those, a very thin black plastic shim completes the job. Plastic cut from very inexpensive school binders works well. Each lens has an adapter that isn't removed. 

 

Small lenses can cause problems. The EL-Nikkors are saved by the large helicoid. Unfortunately, the Petri 2x converter is tiny and requires moving/removing adapters, thus defeating the shims. The slot does nothing on a K-1, except cause light leaks. Saran Wrap is a possibility.

 

@dabateman excellent tips. I have extra adapters and will try the glue. What I really need is a Pentax K-1 with native M42 mount. Pentax is on a retro crusade, perhaps I should petition them to return to screw thread .

 

Thanks,

Doug A

[Andrea B.]

Doug, I didn't quite get why you don't like that first Pentax K-to-M42 adapter?

[Doug A]

@Andrea B. It is the made by Pentax adapter and it is fine. I tend to only use it with wide-angle lenses so they can reach infinity focus. The disadvantage is slower lens changing. The lens has to be unscrewed for removal. To remove the adapter a fingernail is required. The adapter spring can be removed. Then the lens will just come off with a turn- it isn't locked on. If the lens is too small it won't cover the fingernail slot and it is possible to get light leaks while shooting UV. 

 

I have been dedicating an adapter to each lens. That way, once light leaks are cured, nothing changes. The 2x converter messes with the plan :). Just minor annoyances to work through. Now if only something would bloom. 

Thanks,

Doug A