Did Pentax ever change their thread sizes?

[aldrich]

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.

[andrewg_ny]

You can use your 42mm screw-mount lenses on the Pentax K-mount (bayonet) D-SLRs such as K10D with an adapter. Only manual mode will work correctly, as stop-down metering is required. In 'M' mode, pressing the green button will stop down the lens and set the shutter speed appropriately. Holding the DoF preview will allow you to see the light reading in the viewfinder. The shake-reduction feature should work but you'll need to manually enter the lens focal length.

 

The lenses should work OK but there is some question about the exposure accuracy using these lenses on K10D; the other *istD* and K100D may be better at this. It is possible that this will be improved with updates to K10D. The K10D is a nice camera, but any of the (less expensive) Pentax D-SLR will work for you as well, with possibly more consistent exposure.

 

You should also be aware that on all the Pentax D-SLR, due to the fact that the sensor is smaller than a 35mm film frame, there is a 1.5x conversion factor for equivalent field of view. That is, a 50mm lens has an angle of view similar to what a 75mm lens would have acheived on your Spotmatic. Where this will be noticeable will be your wide-angle lenses won't be that wide on the digital body--a 24mm lens on the D-SLR has a field of view close to a 35mm lens on your spotmatic.

 

Hope this helps.

 

-Andrew

[markku_ylilammi]

Did Pentax ever change their thread sizes ?

 

Yes indeed, the very first Asahiflex cameras used a different thread than the later more popular Practica/Pentax M42 thread. I think this old thread was copied from a German brand (Leica ?).

 

Anyway, all Takumars I have seen use the M42 thread.

 

Although the M42/K adapter ring works it has the design flaw that it changes a K-bayonet body into M42-thread body. If all your lenses have a thread mount this is OK. However, if you have both type of lenses this is akward because removing the adapter is a little cumbersome.

 

SMC Takumars are optically superb and they work fine in a DSLR.

[tondegoijer]

Hai,

 

I use the original Pentax adapter and I have no problem whatsoever to quickly remove the adapter from the body. I do not know which adapter Markku Ylilammi is talking about. My advise is, whatever body you get, buy the original Pentax adapter. Lettering engraved in the adapter, not printed on it, names on adapter are Pentax or Asahi Pentax. The Pentax one seems not to have the bottom side finished matt black, the Asahi Pentax does.

 

To get back to the original question, the lenses you use on the spotmatic will fit this adapter.

 

Gr.

Ton

[guido_sardella]

With Pentax K10D you can use your screwmount lenses using a common M42 to K adapter.

 

Once mounted, you loose any aperture automation, so you use the aperture in stopdown,

with manual or aperture priority mode. The only problem is that as you close the aperture

ring, the image in the viewfinder become darker...