[Stone G.]

..........They could indeed have done a better job in this area, but maybe they wanted to push people to buy new lenses, so they didn't waste time to make the adapter story better.

To this and similar entries in this thread: I don't thik this is quite "fair" to Pentax. The adapter was introduced at the same time that Pentax introduced the K-mount in 1975. And it has remained unchanged since then.

Imaging that you were a Spotmatic owner in those days with a significant stock of (excellent and expensive for that time) Takumars. Your beloved Spotmatic dies and you need a new camera body. You would NOT want to buy an entire new set of K-mount optics but rather buy a new body and convert it (reversibly) into an 42-body. And that is the solution Pentax offered their loyal customers then. (Think about other manufacturers - no names mentioned - who have changed their mounts on more than one occasion and supported their existing users with......nothing!).


It is only very recently, that the mixed use of M-42, manual SMC Pentax K, M, and KA lenses together with contemporay fully atomatic lenses have become "fashion" and the adapter was designed at a time where DSLRs were way beyond science fiction.

It is a matter of system design philosophy, but to me, Pentax's choice way back in 1975 makes very good sense - notably, as seen from a user perspective!!!

[Jüri]

I'm not familiar with the Yashica mount, but their registration distance and lens locking mechanism are probably different. Why didn't Pentax change the registration distance? Probably to save cost on changing lens designs. Why didn't they come up with a different locking mechanism that could be used by the adapter as well? I have no idea. They could indeed have done a better job in this area, but maybe they wanted to push people to buy new lenses, so they didn't waste time to make the adapter story better.

Thanks a lot for finally answering what I was asking. The question might have sounded like a rant, but I'm aware of all the benefits Pentax gives me when I want to use older lenses and I'm very happy about it. It's just that every time I put an M42 lens on my Yashica I can't help but wonder why could't it be so easy with Pentax. I mean, there are few people who use Yashica these days, but many who like to use old lenses with their Pentax.

I examined the Yashica mount and found out that the registration distance actually remains the same with both dedicated and M42 lenses, but the locking mechanism is inside the mount, thus the simple and cheap adapters. I guess Pentax just didn't take M42 usability into consideration when designing the K-mount.

[ryan s]

In my opinion, it's two sides of the very same coin.

Pentax did have older users in mind (clearly, with the exact register distance and total diameter of screw mounts in mind when designing the K...and providing an OEM adapter for peanuts [anyone care to look up a genuine Canon FD to EOS adapter price and availability? ])...and at the same time, they did eliminate the auto aperture of screw mount lenses to accommodate the auto aperture of the K lenses.

Somewhat in the same vein of the "crippled" KAF2/3 mounts...we don't have the aperture cam follower for manual K lenses anymore, but they still work fine in M mode and such. And M42s are still usable with even the newest Pentax body in Av or M.

Sure, Pentax could have designed a more elegant adapter...maybe something like an Adaptall. That would have added price and complexity to the system versus a little brass ring Or, they could have just said "too bad" and gone the EOS way. Pentax has survived, Contax and Yashica have not. Unfortunate, but one company's legacy lens adaptation system has outlasted the others...

I guess Pentax just didn't take M42 usability into consideration when designing the K-mount.

Ahh, but they totally did.

[Lowell Goudge]

I guess Pentax just didn't take M42 usability into consideration when designing the K-mount.

I think this is a gross under statement.

If you look at the K mount, pentax has moved forward since going to K mount yet retained compatibility backwards to a great extent.

You need to consider that the move to the K mount was seen with the future in mind, and the need for electrical contacts and accurate rotational regestration of the lens to body.

if you did not need contacts, and accurate regestration the final M42 lenses with auto aperture and open aperture metering is where we would still be.

[Jüri]

Ahh, but they totally did.

Perhaps not enough, since putting the locking mechanism inside the mount had made adapting M42 lenses much easier.

You need to consider that the move to the K mount was seen with the future in mind, and the need for electrical contacts and accurate rotational regestration of the lens to body.

if you did not need contacts, and accurate regestration the final M42 lenses with auto aperture and open aperture metering is where we would still be.

Designing locking mechanism inside the mount does not prevent adding contacts or mean changing registration distance.

[fccwpe]

Just buy inexpensive infinity focus adapters, take off the spring, and leave the adapter on the lens. Voila! A K-Bayonet mount lens.

Hint: unscrew the little screw holding the spring clip to the adapter - discard the spring clip - screw the adapter to the lens - use the little screw in its original hole to secure the adapter to the lens.

Absolutely!!!!! I love my M42's and each has it's own adapter WITHOUT the spring!

[magkelly]

The fact that I can use almost any older Pentax lens on my DSLR delights me to no end. For all the fact that they outsell us the Canikon people cannot say the same. Some lenses fit but a lot don't and I think that's a real shame, for them. There's a lot of good old Canikon glass out there but most of the adapters are far more makeshift than ours and while using them can work sometimes but it's not nearly as easy from what I have seen as using our old lenses on a Pentax. When people talk down Pentax to me this is the first thing I remind myself. We have it pretty good actually when it comes to doing this.

[Laurentiu Cristofor]

To this and similar entries in this thread: I don't thik this is quite "fair" to Pentax. The adapter was introduced at the same time that Pentax introduced the K-mount in 1975. And it has remained unchanged since then.

I think you have missed the point of the OP question and of my response. Jüri rightfully pointed out that the way the M42 adapter locks inside the K-mount could have been better if Pentax would have designed the K-mount lens locking mechanism differently. The adapter cannot be anything else than what it is, once the K-mount is set in stone, so no one is knocking that. It is the K mount that should have been designed to allow an M42 adapter to lock inside the mount the same way that K-mount lenses lock onto the mount.

Pentax could have gone two ways:

1) Keep their current style of lens locking mechanism, but shorten the register distance, so that adapters would look like those that lose infinity focus but lock on the mount like lenses do - of course, with a shorter registration distance, they would no longer lose infinity focus anymore. This would basically offer the mechanical adaptability that Canon EF mount offers today. But this would also imply that you would have to redesign a lens line for the new registration distance, which is costly.

2) Keep the same registration distance, but make the lens to mount locking mechanism such that an adapter that fits inside the mount can use it too - this means the lock would have to be inside the mount - this is a fairly trivial mechanical feat to accomplish.

The question is - why did they not do 2? On second thought, I assume backward compatibility was a secondary goal in the design of the mount - as long as some story could be provided (the one we have today), no one spent resources to polish it.

[Blue]

I think you have missed the point of the OP question and of my response. Jüri rightfully pointed out that the way the M42 adapter locks inside the K-mount could have been better if Pentax would have designed the K-mount lens locking mechanism differently. The adapter cannot be anything else than what it is, once the K-mount is set in stone, so no one is knocking that. It is the K mount that should have been designed to allow an M42 adapter to lock inside the mount the same way that K-mount lenses lock onto the mount.

Pentax could have gone two ways:

1) Keep their current style of lens locking mechanism, but shorten the register distance, so that adapters would look like those that lose infinity focus but lock on the mount like lenses do - of course, with a shorter registration distance, they would no longer lose infinity focus anymore. This would basically offer the mechanical adaptability that Canon EF mount offers today. But this would also imply that you would have to redesign a lens line for the new registration distance, which is costly.

2) Keep the same registration distance, but make the lens to mount locking mechanism such that an adapter that fits inside the mount can use it too - this means the lock would have to be inside the mount - this is a fairly trivial mechanical feat to accomplish.

The question is - why did they not do 2? On second thought, I assume backward compatibility was a secondary goal in the design of the mount - as long as some story could be provided (the one we have today), no one spent resources to polish it.

actually, Asahi Optical probably assumed that most people would prefer to use one adapter on a camera body for several m42 lenses rather than paying the equivalent of $31 per adapter. Once the adapter is installed, adding and removing a Takumar is the same as on a m42 Asahi body.

[Blue]

I think the OP does not have an Origonal adaptor and does not fully understand the use

You put the adaptor on the lens and then insert it no tool required. The adaptor stays in the body and makes it a screw mount body. To remove the adaptor takes a ball point pen or other similar object to release the holding tang. No tool necessary

There is also no loss of infinity focus

Loss of infinity focus is with third party adaptors not pentax ones. Tools come with third party adaptors not pentax ones

Lowell nailed it. There has never been a tool for a genuine Asahi Optical Pentax adapter or Pentax adapter. Its the 3rd party ones that provide a mini crowbar.

[ryan s]

Even if the M42 adapter was removable using the lens release button (I, too, wish it were), why would Pentax take the time and money to do it when they could just design a big nut instead?

And in the end, the adapter would stay in the mount regardless of whether or not it was the design they went with, or tooled the initial K design differently to use the lens release button.

My biggest gripe is that the lens is "loose" when the body of the lens doesn't contact the metal camera mount. They should have changed that, IMO.

[Lowell Goudge]

Designing locking mechanism inside the mount does not prevent adding contacts or mean changing registration distance.

No it does not,

The fact is, that it is only the non pentax M42 adaptors that change regestration distance by adding the use of the K mount lens locking pin.

the addition of contacts did necessitate a much wider flange and lens base than the M42 mount since most of the internal diameter inside the M42 mount can be occupied by the lens itself and rear elements, there was no where but outside for many contacts, and the lens flange makes a good location. Inside would be tight on some lenses.

As far as I am concerned, the overall arrangement is good, and much better than canon, who abandoned their lens mount compatability not once but twice.

At any rate, this decision happened in 1975, so it is not a question of why their mount today makes it difficult to use M42 lenses, we are discussing here issues relating to using lenses that are 45-60 years old, on a brand new camera. The fact that every pentax digital camera can use these lenses, and in fact any lens you can mount onto it, as opposed to canon who abandoned their old lenses, and nikon, where you need to get a pro model to even meter with the lens, says something about pentax and their comittment to older systems.

Stop complaining and go out and shoot

[Blue]

Not only did Canon dump the FD mount as Lowell pointed out, they shorten the registration distance thereby orphaning all FD L glass and other L glass of interest except for a few very special applications such as a macro mount to use MD on ef or the FD bellows on the ef.

Edit: Furthermore, Canon never really planned it for other mounts to be adapted to their digital bodies. It just happened and those adapters are by third parties. If Canon had planned on people using some of the special rangefinder glass or Pentax's K or A 50/1.2, those people wouldn't be shaving the mirrors on the full frame digital canon bodies.

[ryan s]

I'm sure it was a slip, but the EOS registration is slightly longer than FD I know you know what's going on

That's also how Canon EOS cams have a heck of a lot of adapters and adapters with flanges--the register is still shorter than other systems (OM, F mount, K mount, Leica R, etc). Putting lenses with shorter register distances than the body is where infinity focus is lost

[Stone G.]

actually, Asahi Optical probably assumed that most people would prefer to use one adapter on a camera body for several m42 lenses rather than paying the equivalent of $31 per adapter. Once the adapter is installed, adding and removing a Takumar is the same as on a m42 Asahi body.

Exactly my point above too - and therefore I am opposing the suggestion that ".........maybe they wanted to push people to buy new lenses, so they didn't waste time to make the adapter story better". Pentax had their existing customers (Takumar owners) in mind at that time.