[krypticide]

For you heavy M42 len users out there: do you have just one M42 screw adapter for all your lenses, or do you get one for each of them?

I currently only have one lens (135mm f/3.5): are there any problems with leaving the adapter on the lens all the time?

[Stratman]

I only have one, and I NEVER leave it on a lens, I just attach it to the camera when I want to use my Takumars.

[chedoy]

The kicker is that the adapter has a spring clip that locks it into the body. When you remove the lens, the adapter will stay in the body and depending on the fit, may require the adapter tool for removal.

Some owners remove the clip, glue the adapter to the lens, and rely on friction to keep the lens from falling off.

Some of the M42 lenses are large enough to cover the retaining pin used by the bayonet mount lenses. A small recess could be cut on these lens barrels to use the pin.

None of my M42's are big enough to cover the pin. I've considered adding a flange with epoxy to utilize the pin.

[krypticide]

I see what you mean about the spring clip: just experienced it myself. Would have been nice to have the option to leave the adapter on the lens and take it off like a regular bayonet, but there were probably mechanical restrictions...

[cpopham]

The official name for the Pentax adapter is "Mount Adapter B". It's a mount adapter (e.g. the on camera mount) and NOT a lens adapter...

Also, I'm not exactly a heavy screw mount lens user, but I do find that when I'm in the mood to use them, I'l usually use only use on screw mount lenses for a whole session, so having to remove the adapter from the camera isn't a big pain.

[hinman]

I have few blog posts on M42

Hin's Tech Corner Search on M42

and I use both methods. For the genuine Pentax adapter, I always use it mounted on the body first. But for the 3rd party adapters, I take out the spring plate and mount it on the lens. The K mount rear cap can serve as to screw and unscrew the adapters in and out of your M42 lens.

Thanks,
Hin

[monochrome]

[, , , ] The K mount rear cap can serve as to screw and unscrew the adapters in and out of your M42 lens.

Thanks,
Hin

I like it!!

[Just1MoreDave]

I have adapters for each M42 lens, with the spring removed so they are kind of like a K-mount. It works out well for small primes. Larger and heavier lenses such as my Vivitar/Komine 200mm f3.5 push the limits of this method. Also lenses that have stiff controls don't work well.

Cpopham mentioned one point that I agree with. Each type of lens needs a different mindset and has different compatibility. Although my lenses are sort of like a K-mount, in actual use I must remember they are not. The one adapter per lens system can cause trouble when I forget what each lens needs.

[straightshooter]

I have just one adapter and I leave it in the camera if I'm using more than one M42 lens. Otherwise, it stays in the bag since I also use my M42 lenses on M42 mount cameras.

CW

[Maffer]

I have the original Pentax adapter and it is relatively painless to use requiring no tools to get it off the body. You can get it off by pressing the leaf spring with your finger nail (I use my thumb for this) and while holding the notch at the opposite side with the nail of your index finger just screw the thing off. Time required to attach the adapter equals the time spent when changing a normal K-mount lens with a little practise.

[dlacouture]

I tend to have one adapter per lens, as I now have 4 M42 lenses and regularly switch between those...

For the slim lenses that don't cover the locking pin (or the larger ones you really don't want to savagely drill!), I found that adding a thin metallic flange (about 0.3mm and actually made out of a jam lid!) between the adapter and the lens, then drilling a hole for the locking pin, just works all right...
While infinity focus supposedly could not be achieved with this extra 0.3mm, I found that it's not a problem in real life...
I'll try to post some pics...

[John Kovarik]

Keep in mind that removing the spring makes the lens/body connection 'unlocked'. Depending on how tightly the adapter fits it may be that friction alone will not be enough to prevent the lens from turning enough to fall off...............

[Gooshin]

if a lens is wide enough that its base covers the locking pin in your body, you can permantly leave the adapter on, take off the locking plate on the adapter, and drill a small hole in the lens for the locking pin.

if however, as the case for a good portion of takumar lenses, the body is so narrow that it bypases the locking pin all together, it would be futile to have an adapter for each lens, since you would never be able to lock your lens on to the camera.

this has been said with first-hand experience