Did Pentax ever change their thread sizes?

I have an Asahi Pentax Spotmatic F with several lenses. I am salivating over

the idea of dropping $900 for the Pentax K10 DSLR, and being able to use every

lens I already have. $900 out, for what would be over $3000 in accessories

today. Will this work? IS quality an issue? I've heard mixed on that.

Pentax always used the M42 thread mount and I believe the Pentax digital SLRs can use virtually all of them--one of the advantages of the Pentax digital cameras.

Of course not all Pentax film cameras use the M42 thread mount, this applies only to early models. Later models used the K bayonet mount, also known as PK mount (Pentax K mount). But I do not know whether there are adaptors to convert M42 thread mount lenses to PK bayonet mount or to fit to Pentax digital cameras.

Spotmatic F only takes screw mount lenses, in M42 thread, these will NOT Work on any of the Pentax DSLR's unles an M42 to PK adapter is purchased, and even so you will lose the ability to meter properly.

 

I have a Nikon D70S on which I intended to used my vintage nikon lenses. ALAS, out of my 5 lenses 3 of them were made for the original Nikon F which debuted in 1959 and these do not fit on My D70S. Even though the mount matches(Nikon F mount) the barrel of the lens in the back, sticks too much out inside the mount and gets stopped by CPU contacts inside the mount. Good luck

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Yes, prior to the 42mm screw, Pentax ( Asahiflex ) utilized 37mm screw mount lenses.<p>

Dan<p>

<a href="http://www.antiquecameras.net">www.antiquecameras.net

While its true that Asahiflex cameras used a 37mm thread, these lenses are extremely rare and expensive. The first Asahi camera to use the name Pentax, was the model K (1957 ??), which also introduced the M42 thread.

 

So, any lens that is properly called a "Pentax" screwmount, will use an M42 thread. That includes all variants of the Spotmatic.

 

Of course, using an M42 lens on a K10D, you will lose all the automatic functions of the camera, including the aperture. A K10D will not even stop an M42 lens down at the moment of exposure, let alone do wide-open metering or autofocus. If you use the Super-Multi-Coated Takumar lens from a Spotmatic F, it must be switched to M on the lens and use stop-down metering. But you probably already know all that.

 

As for quality, some of the old Pentax M42 lenses (if they're genuine Pentax lenses) are second to none, optically.

 

Paul Noble

"Pentax always used the M42 thread mount"

 

WRONG!!! early Pentax SLRs used a different screw mount.

I have an old 50/2 Auto Takumar. It has the M42 thread but the back focus is different and it won't work on any of the newer M42 bodies I have.

The Auto-Takumar is broken then, since it was for Pentax/Contax-S mount. Someone took it apart and put it together wrong.

As far as using the Pentax and other M42 lenses, all I can say from my own experience with my Pentax ist DS is: the lenses work very nicely and I have not encountered metering problems. Manually stopping down & manual focusing takes a little extra time but no big deal as long as you can accept those limitations. In the real old days most all lenses worked that way. The Pentax digital cameras use a K (PK) mount so you can also use the older lenses from Pentax & other PK mount cameras which are quite common and normally very good quality. At least some if not all of those PK auto lenses will actually stop down automatically if you use the digital's M (manual) mode and press the AE-L button to temporarily stop the lens down. That's how it is with the ist DS anyway. There are many websites that describe & illustrate the use of older film camera lenses on digital cameras such as Canon EOS and Pentax. I like the affordable Pentax ist DS because it uses a bright pentaprism, cost less than $400 with a Pentax zoom lens and most of all I can enjoy using my old pre-70 M42 lenses. Canon EOS mount offers even more choices in adapters so maybe some Canon DSLR are fine too. Sorry to wonder off topic into digital land. I know some in the forum hate that sort of thing.

Yep, the AsahiFlex used a Leica thread lens mount, of course the mount to film distance was greater so Leica lenses wouldn't focus to infinity. I have the AsahiFlex my father bought in the mid 50's. Its a pretty little thing; resembles an old Leica, with a front-mounted slow speed dial. The top shutter speed dial rotated when the shutter was released, my father, left-handed and left eyed lost some shots when his nose fouled the dial. ;-) Waist level finder only, with an auxillary optical eye-level finder for 50mm action shots. I also have, in addition to the 50mm f3.5, a 35mm and an 83mm f1.9. This latter is an impressive hunk of glass, quite sharp stopped down to f2.8 or so. BTW, I think that Asahi was the first to use an instant return mirror. I hope to get this old gem working, for sentiment if nothing else. Any suggestions for a good shop?

" Yep, the AsahiFlex used a Leica thread lens mount, ....".

NO !: Leica mount is 39mm, "standard" mount is 42mm and Asahiflex is 37mm