Helios in PK mount

**GUB** · 10-01-2019, 12:32 AM

Originally posted by ZombieArmy

I've used the 44-2 for years and in my experience the only way light leaks ever become apparent is in long exposures. In those cases I just use a scrunchie or rubber band to cover the hole.

That is interesting - made me have a look . When you examine the adaptor closely you can just see that the notch that the spring sits across is slightly deeper cut than the other notch. (And I am looking at Pentax branded ones as well as el-cheapos). Maybe it is the common practise of removing the spring that is the problem. The slightly compressed spring baffles the light. The non spring side has slightly more wall so it doesn't leak on that side. I have certainly experienced the light leak but it may well have been a modified adaptor.

EDIT Update - it was so obvious I should have seen it before! Take a look at the thread on the adapter and see the great notch cut into it on the spring side. Take the spring off and the light pours in! On the other side the threaded tube baffles the light path.

Last edited by GUB; 10-01-2019 at 03:29 AM.

stevebrot · 10-01-2019, 12:15 PM - **1 Like**

Originally posted by GUB

EDIT Update - it was so obvious I should have seen it before! Take a look at the thread on the adapter and see the great notch cut into it on the spring side. Take the spring off and the light pours in! On the other side the threaded tube baffles the light path.

On the genuine Pentax, the spring does not fully baffle the cut-out, so there might still be a problem with that adapter.

Steve

**GUB** · 10-01-2019, 01:06 PM

Originally posted by stevebrot

On the genuine Pentax, the spring does not fully baffle the cut-out, so there might still be a problem with that adapter.

Steve

But when the adaptor is in place the spring is compressed a little which closes things up a bit. But I have to emphasise this is only an issue with the occasional lens that has a small diameter barrel and not any Takumars.

**BigMackCam** · 10-01-2019, 02:19 PM

Originally posted by GUB

But when the adaptor is in place the spring is compressed a little which closes things up a bit. But I have to emphasise this is only an issue with the occasional lens that has a small diameter barrel and not any Takumars.

It's an issue for a number of Soviet M42 lenses... Helios 44-2, Industar 50-2 and Mir-1 spring to mind, but as I recall there are others (it's a while since I've mounted my Soviet lenses on my K-3). Where closer range focus is acceptable, I prefer to use one of the M42 adapters that sits on top of the camera's mount. It prevents longer distance and infinity focus, of course, but covers all of the contacts and has no cut out slots. Otherwise, some form of elastic or rubber band / washer can sometimes be used to cover the slots on the flush-fitting adapters:

Preventing M42 adapter light leaks and dust ingress - an easy solution! - PentaxForums.com

**Billy Joe** · 10-01-2019, 11:54 PM

Well this completely has me scared to consider Pentax full frame... I used my M42 Helios lenses on a Sony full frame and had no issues with light leakage.

How can this be a problem with a K-mount?

---------- Post added 10-01-19 at 11:55 PM ----------

Is this also going to be a problem on a KP? An issue with the adaptor/lens combo?

**GUB** · 10-02-2019, 02:55 AM - **1 Like**

Don't over react. Understand the issue by reading Mikes link above and choose your solution - it is not a biggie!. Because Zombie Army doesn't have an issue with it then I am guessing that an adaptor still in original condition (with spring) will be fine. But it is simple prevention to use a large rubber o-ring or a hair scrunchie on the lens. Or buy a cheap non infinity adapter - they are totally light proof.

**BigMackCam** · 10-02-2019, 03:28 AM

Originally posted by Billy Joe

Well this completely has me scared to consider Pentax full frame... I used my M42 Helios lenses on a Sony full frame and had no issues with light leakage.

How can this be a problem with a K-mount?

As @GUB says, don't be concerned.

The reason it wasn't an issue with your Sony gear is that the registration distance between sensor and mount is smaller, so the adapter for M42 is longer and can therefore sit right on top of the camera's mount. With Pentax, the K-mount registration distance is exactly the same as M42, so the adapter has to sit inside the camera's mount - i.e. it can't protrude further than the edge of the mount (this is why adapters that cover the camera's mount won't allow infinity focus, as they're pushing the lens further forward). The slots in the Pentax M42 adapter are essential to allow fitting and removal.

It's worth noting that M42 (or any other mount) adapters for Sony come with their own set of problems - for example, lateral movement that can result in de-centered positioning, poor machining and construction that can result in tilted mounting of lenses and a plane of focus that isn't completely parallel to the sensor, internal reflections that can lead to veiling flare and strange artefacts on photos, etc. You may not have noticed these when shooting adapted lenses on Sony, but I can almost guarantee you've experienced it, even if you didn't realise. I shoot an A7 MkII with various adapters for my vintage lenses, and over time I've had all of the problems I mentioned.

Originally posted by Billy Joe

Is this also going to be a problem on a KP? An issue with the adaptor/lens combo?

Yes, but it's really not a problem. Just a quirk that you need to work around, and it's easy to do. Just review that link I posted

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10-01-2019, 12:32 AM	#16
GUB Loyal Site Supporter Join Date: Aug 2012 Location: Wanganui Photos: Gallery \| Albums Posts: 5,760	Originally posted by ZombieArmy I've used the 44-2 for years and in my experience the only way light leaks ever become apparent is in long exposures. In those cases I just use a scrunchie or rubber band to cover the hole. That is interesting - made me have a look . When you examine the adaptor closely you can just see that the notch that the spring sits across is slightly deeper cut than the other notch. (And I am looking at Pentax branded ones as well as el-cheapos). Maybe it is the common practise of removing the spring that is the problem. The slightly compressed spring baffles the light. The non spring side has slightly more wall so it doesn't leak on that side. I have certainly experienced the light leak but it may well have been a modified adaptor. EDIT Update - it was so obvious I should have seen it before! Take a look at the thread on the adapter and see the great notch cut into it on the spring side. Take the spring off and the light pours in! On the other side the threaded tube baffles the light path. Last edited by GUB; 10-01-2019 at 03:29 AM.

10-01-2019, 12:15 PM - 1 Like	#17
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by GUB EDIT Update - it was so obvious I should have seen it before! Take a look at the thread on the adapter and see the great notch cut into it on the spring side. Take the spring off and the light pours in! On the other side the threaded tube baffles the light path. On the genuine Pentax, the spring does not fully baffle the cut-out, so there might still be a problem with that adapter. Steve

10-01-2019, 01:06 PM	#18
GUB Loyal Site Supporter Join Date: Aug 2012 Location: Wanganui Photos: Gallery \| Albums Posts: 5,760	Originally posted by stevebrot On the genuine Pentax, the spring does not fully baffle the cut-out, so there might still be a problem with that adapter. Steve But when the adaptor is in place the spring is compressed a little which closes things up a bit. But I have to emphasise this is only an issue with the occasional lens that has a small diameter barrel and not any Takumars.

10-01-2019, 02:19 PM	#19
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,670	Originally posted by GUB But when the adaptor is in place the spring is compressed a little which closes things up a bit. But I have to emphasise this is only an issue with the occasional lens that has a small diameter barrel and not any Takumars. It's an issue for a number of Soviet M42 lenses... Helios 44-2, Industar 50-2 and Mir-1 spring to mind, but as I recall there are others (it's a while since I've mounted my Soviet lenses on my K-3). Where closer range focus is acceptable, I prefer to use one of the M42 adapters that sits on top of the camera's mount. It prevents longer distance and infinity focus, of course, but covers all of the contacts and has no cut out slots. Otherwise, some form of elastic or rubber band / washer can sometimes be used to cover the slots on the flush-fitting adapters: Preventing M42 adapter light leaks and dust ingress - an easy solution! - PentaxForums.com

10-01-2019, 11:54 PM	#20
Billy Joe Site Supporter Join Date: Jun 2013 Posts: 374	Well this completely has me scared to consider Pentax full frame... I used my M42 Helios lenses on a Sony full frame and had no issues with light leakage. How can this be a problem with a K-mount? ---------- Post added 10-01-19 at 11:55 PM ---------- Is this also going to be a problem on a KP? An issue with the adaptor/lens combo?

10-02-2019, 02:55 AM - 1 Like	#21
GUB Loyal Site Supporter Join Date: Aug 2012 Location: Wanganui Photos: Gallery \| Albums Posts: 5,760	Don't over react. Understand the issue by reading Mikes link above and choose your solution - it is not a biggie!. Because Zombie Army doesn't have an issue with it then I am guessing that an adaptor still in original condition (with spring) will be fine. But it is simple prevention to use a large rubber o-ring or a hair scrunchie on the lens. Or buy a cheap non infinity adapter - they are totally light proof.

10-02-2019, 03:28 AM	#22
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,670	Originally posted by Billy Joe Well this completely has me scared to consider Pentax full frame... I used my M42 Helios lenses on a Sony full frame and had no issues with light leakage. How can this be a problem with a K-mount? As @GUB says, don't be concerned. The reason it wasn't an issue with your Sony gear is that the registration distance between sensor and mount is smaller, so the adapter for M42 is longer and can therefore sit right on top of the camera's mount. With Pentax, the K-mount registration distance is exactly the same as M42, so the adapter has to sit inside the camera's mount - i.e. it can't protrude further than the edge of the mount (this is why adapters that cover the camera's mount won't allow infinity focus, as they're pushing the lens further forward). The slots in the Pentax M42 adapter are essential to allow fitting and removal. It's worth noting that M42 (or any other mount) adapters for Sony come with their own set of problems - for example, lateral movement that can result in de-centered positioning, poor machining and construction that can result in tilted mounting of lenses and a plane of focus that isn't completely parallel to the sensor, internal reflections that can lead to veiling flare and strange artefacts on photos, etc. You may not have noticed these when shooting adapted lenses on Sony, but I can almost guarantee you've experienced it, even if you didn't realise. I shoot an A7 MkII with various adapters for my vintage lenses, and over time I've had all of the problems I mentioned. Originally posted by Billy Joe Is this also going to be a problem on a KP? An issue with the adaptor/lens combo? Yes, but it's really not a problem. Just a quirk that you need to work around, and it's easy to do. Just review that link I posted