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Pentax Mount Adapter K (M42 Screwmount to K Mount) Review RSS Feed

Pentax Mount Adapter K (M42 Screwmount to K Mount)

Reviews Views Date of last review
18 61,941 Mon February 19, 2024
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Recommended By Average Price Average User Rating
100% of reviewers $30.29 9.35
Pentax Mount Adapter K (M42 Screwmount to K Mount)

Pentax Mount Adapter K (M42 Screwmount to K Mount) Pentax Mount Adapter K (M42 Screwmount to K Mount)
supersize
Pentax Mount Adapter K (M42 Screwmount to K Mount)
supersize
Pentax Mount Adapter K (M42 Screwmount to K Mount)
supersize

Description:

This adapter allows the use of M42 screw mount lenses on Pentax Bayonet cameras (film and digital), in manual or Av exposure modes. You will have to stop the lens down manually to the shooting aperture since there is no linkage between the camera and a screw mount lens.

Installing the adapter in the mount can be fiddly. The easiest way to do it is to first screw the adapter onto a lens, then mount the lens (with adapter), and finally screw the lens out leaving the adapter in place on the camera.

This genuine Pentax adapter sits flush with the surface of the camera's bayonet which allows the M42 lens to focus to infinity. Third party adapters with a flange should be avoided - they prevent the lens from focusing to infinity.


Pentax Mount Adapter K (M42 Screw Mount to K Mount)
© www.pentaxforums.com, sharable with attribution
Image Format
Full-frame / 35mm film
Lens Mount
Pentax K
Light Loss
0 stops
Magnification
1x
Optics
0 elements, 0 groups
Mount Variant (Rear)
K
Mount Variant (Front)
M42 (Conventional)
Focusing
Manual
Coating
Weather Sealing
No
Case
Diam x Length
Weight
0
Production Years
(in production)
Notes
User reviews
This adapter allows for mounting M42 screw mount lenses on a K-mount camera.
The only exposure modes supported are M and Av with stop down metering, and Bulb.
The adapter has no provision for the camera stopping the aperture down.

Features:
Full-Frame Support
Price History:



Add Review of Pentax Mount Adapter K (M42 Screwmount to K Mount)
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Sort Reviews by: Date | Author | Rating | Recommendation | Likes (Descending) Showing Reviews 1-15 of 18
Senior Member

Registered: June, 2020
Location: Guangdong
Posts: 173
Review Date: February 19, 2024 Recommended | Price: $20.00 | Rating: 8 

 
Pros: work both on film and digi body, durable
Cons: some (perhaps many?) of them can't posit the lens correctly to the central

It's overpriced on market. Yes it's easy to install and is durable. But I've seen more than 1 of them that can't place the lens correctly to the central position. Though this won't really affect taking photos I do wish they can be more precise.
   
Site Supporter

Registered: May, 2023
Location: Northwest Wyoming
Posts: 160
Review Date: February 17, 2024 Recommended | Price: $25.00 | Rating: 10 

 
Pros: Allows use of film-era lenses on new digital cameras
Cons: Price

I bought the Pentax adapter in 2007 when I bought my first DSLR (K100D) thinking I'd be using my old lenses, but it turned out to mostly just sit in it's little envelope in the camera box. I don't remember what I paid for it back then so $25 is a guess.

Now that I've added a couple of K20D's I dug it out and it's pretty much permanently on the K100D. So far I've used my dad's old SMC 55mm/f1.8, my SP500 SMC 55mm/f2.0 kit lens, my treasured SMC 135mm/f2.5, and a purchased used Tele Takumar 400mm/f5.6. They all work well with the exception of an Av exposure issue on the 135mm that I got some help with here on the PF.

But as a back-up I bought an Urth adapter which, other than the inscription, appears identical to the Pentax adapter and works equally well. All lenses focus to infinity.

In my opinion the colors rendered by the old SMC Takumars is better than the modern lenses, particularly the red/orange/yellow of the spectrum (only the 55mm/f2.0 is tinged a little, probably thorium glass).

Being able to use legacy glass on a digital body was a big factor in sticking with Pentax product for me, and I'm glad I've finally taken advantage of that in the past year.
   
New Member

Registered: July, 2013
Posts: 2
Review Date: January 22, 2024 Recommended | Price: $48.00 | Rating: 8 

 
Pros: Infiinity focus
Cons: Price

Just acquired my first M42 lens, a Takumar SMC 200mm f4. Wasn't interested in dealing with focus or interface issues that I've read about using the cheap knock-off adapters, so I ponied up the money for a genuine Asahi Pentax example. The Takumar is going to be dedicated to astrophotography, so infinity focus is critical. As another poster noted, Pentax is still producing these in the Phillipines, and they run about $100 new. I think the $48 for the vintage model I bought is too much, and these things don't exactly degrade with time or (proper) use, so a new one was out of the question.

Anyway, I tested the Asahi adapter with my K-50 and the Takumar - all good. My rating is tempered by how much these little rings of machined metal cost.
   
New Member

Registered: July, 2008
Location: Wisconsin
Posts: 3
Review Date: January 20, 2024 Recommended | Price: $30.00 | Rating: 9 

 
Pros: Optimal adapter for Pentax M42
Cons: Not all M42

I have 3 of them & work perfect for PENTAX M42 lenses mounted on K mount cameras.

Some 3rd party brands of M42 mount lenses do not seat properly, including several Yashica and Mamiya/Sekor lenses I have tried.
Severe issues with tightening, seating, wobble & misalignment are evident.

I use M42 lenses with other adapters for mirrorless cameras such as Fujifilm & have no issues or problems.
   
Senior Member

Registered: July, 2023
Posts: 256
Review Date: October 5, 2023 Recommended | Rating: N/A 

 
Pros:
Cons:

Seems price has gone up ... a LOT! B&H Photo sells the Pentax one for $99.95 now.
https://www.bhphotovideo.com/c/product/673977-REG/Pentax_30120_Mount_Adapter_K.html

I got one when I bought the K3 Monochrome. It does say PENTAX etched on the adapter along with Philippines where it was made. Instruction set came with the Ricoh Pentax name change flyer and the isntruction sheet. It seems the real one.


However, when I mount an old Super-Takumar lens the red focus index mark is around the 10 o'clock postion looking at it from the front. The lens red index is not on top where I would have expected it to be. Two lenses too.

Also, the camera's metering system does not work with it. No indication on opening or closing it down on the meter's bargraph. Don't know what is going on there, other than maybe the camera needs some info from the K-mount lens contact pins for it to work. Odd.
   
New Member

Registered: November, 2019
Posts: 1
Review Date: March 20, 2023 Recommended | Price: $35.00 | Rating: 10 

 
Pros: Precision made, works exactly as it should do.
Cons: None

I have two of these, I paid approx. $35.00 for each of them, here in England.

Very well engineered Pentax product. Releases from your camera body without problem, if you find one that comes with its release key
   
Forum Member

Registered: March, 2011
Location: Ontario
Posts: 89

1 user found this helpful
Review Date: December 1, 2019 Recommended | Price: $15.00 | Rating: 10 

 
Pros: It does what it supposed to.
Cons: Cost makes no sense

It delivers 100% on what it is supposed to.

The price is just outrageous though, The $15 I paid for mine was outrageous. I'm thinking of sending mine to a machining company in China to get them duplicated so I can sell them for $10 and make $9.50 apiece. I'll be rich in no time.


But hey, if you need one, you need one. Market economics
   
amateur dirt farmer

Registered: December, 2014
Location: probably out in a field somewhere...
Posts: 41,257

1 user found this helpful
Review Date: November 26, 2018 Recommended | Price: $20.00 | Rating: 10 

 
Pros: proper fit, easy to remove (if needing to do so)
Cons: new prices can be prohibitive - look for a good, used copy

mine came in a bundle with a couple of other accessories and then sat in a box for a couple of years...

finally became confident enough to buy an M42 lens (Super Takumar 55mm f1.8) and tried it initially on one of my K-3 bodies....

liked it well enough to buy a dedicated-body to be my M42 DSLR and mounted this adapter on the camera, with the intent to never remove the adapter...


it does what it's intended to do perfectly: allow you to use M42 mount lenses on a K-mount body


a comment on current pricing - I noticed that B&H currently has them listed at $79.95, which seems ridiculously high.... check the Marketplace here, post a 'Wanted' ad, and look also on eBay for a good used copy....

used copies will still be higher than knock-offs, but you'll be getting an adapter that is designed for your camera and less likely to leave you with it stuck on the body...
   
Loyal Site Supportaxian

Registered: September, 2013
Location: Texas
Posts: 503

1 user found this helpful
Review Date: December 3, 2016 Recommended | Price: $45.00 | Rating: 10 

 
Pros: Precise.
Cons: none.

The real deal. Superior to cheap knock-offs. This is the one you want.
   
Loyal Site Supporter

Registered: July, 2010
Location: NW Ohio
Posts: 2,081

1 user found this helpful
Review Date: September 13, 2015 Recommended | Price: $30.00 | Rating: 10 

 
Pros: it works, it's high quality, worth the price for peace of mind
Cons: None

It does the job while providing peace of mind. What more can I say? It's a simple device but some of the most simple things can cause a lot of pain in time and money. This little gadget simply does what it was designed to do. I would not trust a non-Pentax adapter on my camera.
   
Forum Member

Registered: September, 2012
Location: Tokyo
Posts: 72

1 user found this helpful
Review Date: October 25, 2012 Recommended | Price: $12.00 | Rating: 10 

 
Pros: It works
Cons: Getting expensive

Does what it says. I have both the "Japan" labelled Pentax one and the "Philippines" labelled one. They seem to be identical. In Tokyo, only the Philippines labelled one is widely available, and costs upwards of $50 equivalent. The Japan labelled one I found in a dusty shop in Ginza, in a big cardboard box of bits and bobs. The shop asked for 1000 yen ( $12 ) which I happily paid.

I leave the clips on, it's no hardship to remove the adapter from the body.

Paul
   
Pentaxian

Registered: April, 2011
Location: Lost in translation ...
Posts: 18,076

2 users found this helpful
Review Date: March 26, 2012 Recommended | Price: $25.00 | Rating: 9 

 
Pros: Works great, safest investment in the long run
Cons: None really - maybe see previous reviews

Bonjour,

This was a no-brainner for me because I have no brain and I wanted a near "zero risk" mount my newly acquired Super-Tak 55/1.8 on the brand new K-5. Gladly paid a few bucks more for having a lot of security here ... what is it, "Penny wise and pound foolish"?

Just basiclly asked myself the following: "OK, so the adapter is going to cost about 25 bucks ... not the cheapest about town ... but, how much is it going to cost me in bank funds, lost time to repair and general (in)sanity if a cheaper adapter gets jammed on the K-5?" Again, a no-brainner for me without a brain.

Salut et bon courage, J Frog
   
Loyal Site Supporter

Registered: November, 2007
Location: Sparwood, BC, Canada
Posts: 12,385

1 user found this helpful
Review Date: January 26, 2012 Recommended | Price: $35.00 | Rating: 10 

 
Pros: The perfect M42 adapter
Cons: None that I know of

This is the only adapter that reliably does what it is supposed to do. I've had one since the mid 1970s when I bought my first K mount camera. It clicks in solidly. It allows infinity focus. My M42 lenses fit tightly. The adapter goes on off with a fingernail. I am too anal to not use the clip.

I am astonished at those who want to save $20 and buy a cheap adapter that may or may not be easy to install or remove, or might not even allow infinity focus.
   
Site Supporter

Registered: November, 2010
Location: California
Posts: 2,223

1 user found this helpful
Review Date: July 26, 2011 Recommended | Price: $45.00 | Rating: 10 

 
Pros: The best thing Pentax made to allow use of M42 lenses
Cons: Genuine Adapter is great, come copies are not. Bowers is good.

This adapter is the best thing since sliced bread. There are some cheap Chinese copies that can work, but no infinite. The Bower is well done and works fine. I had many problems trying to use M42 lenses and the adapters because I did not have instructions. However, when I bought the genuine Pentax / M42 adapter, it came with instructions and it works MARVELOUSLY. The truth is that I was then able to use my Bower adapter and found that it also works just fine. The main mistake: I was attaching the adapter to the lens, and that is not the correct way to do it. The adapter has to be attached to the camera, then the lens is screwed in and voila'. To remove the genuine adapter, you pinch the spring with a ballpoint pen and rotate and done. The Bower brings a tool to lose the spring and rotate at the same time, so it is indeed easier to use. Go and enjoy the M42 legacy lens. Here is a transcript of the instructions to install and remove the adapter:
1) Fit the adapter, matching the red dot of the adapter with the red dot of the body mount.
2) Turn the adapter clockwise until it stops (65 degrees) by using a ball-point pen or the like to lock it. Then screw-mount lenses can be used.
3) TO remove the adapter, push the spring with a ball-point pen and turn the adapter counter-clockwise until it stops.
   
Moderator
Site Supporter

Registered: June, 2008
Location: Florida Hill Country
Posts: 17,377
Review Date: August 10, 2010 Recommended | Price: $30.00 | Rating: 9 

 
Pros: well made and precision fit
Cons:

The genuine Pentax adapter can easily be removed with a finger nail. It allows infinity focus and is precision fit. The only improvement would be to have the inner ring to depress the auto aperture actuation pin like some other makers did such as Mamiya for auto aperture lenses that lack an A-M switch.
Add Review of Pentax Mount Adapter K (M42 Screwmount to K Mount)



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