I think that most lenses would outperform the 18-50 kit lens (I have one, hardly ever use it)
You do not need an adaptor for your K lenses, but there are some issues worth mentioning.
The SA mount is physically a Pentax K mount, and electrically a Canon EF mount. Many K mount lenses will fit the SD14, but as Klaus says, you may have to hack of the lever. Check first what you can sell these lenses for before deciding.
Next, make sure that the rear of the lens do not protrude too far into the camera body when mounted. Some lenses may hit the dust protector.
As stated, the registration distance differs: SA 44mm, and Pentax K 45,6mm. This means that the K lens will be closer to the sensor than it should be. The result is as Klaus says, it focuses past infinity - but it also affects the closest focusing distance; beeing longer.
A solution would be (if you already have hacked off the lever) to ADD a 1,46mm spacer (and longer screws, obviously).
The Canon lens you mention is of particular interest if it is a EF mount lens. With some work, you can retain both AF and AA (if the lens have it, that is).
You get hold of a SA lens mount, and desolder the contacts. If I recall right, they should then be resoldered in the opposite order.
If it is a FD lens, you have two options
a) an optical adapter - loosing quality.
b) grinding off 2mm of the mounting boss.
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For more information about lens conversions, have a look at my Non Sigma Lens compendium at:
And a near complete drawing:
My lens budget is quite small but I'd be willing to do the extra work required to adapt other lenses as long as the results could be OK. Until now I have had only one lens, the Sigma 18-50mm DC kit lens.
But I found a box of dead Pentax cameras and some lenses.
Camera: Pentax MV1
Lens: SMC Pentax-M 1:1.7 50mm
Lens: Sears model 202 Multicoated 1:4.0 80-200mm (ca. 1982)
Camera: Pentax ZX-M
Lens: SMC Pentax-A 1:4-5.6 35-80mm
Would any of these lenses be worth the effort of adapting to the SD14. It would be nice to have a prime lens and a zoom, even if they would be manual operated. What adapters (if any) would be needed?