Originally posted by Rondec The lightest Pentax cameras that I have used are the K-S1 (very compact, but prone to dark frame aperture block issues), K-m and, K-x. The K-70 weighs 688 grams, the K-S1 was 558 grams, the K-x series cameras were around 588 grams (the K-r was 598).
I agree re the K-S1, which I have had from new. Mine did suffer from the aperture solenoid failure, but there is an excellent thread on this forum regarding the repair of this, and having done this using a genuine ( note the word!) Pentax upgraded solenoid, it is not a difficult repair. But not every camera that can suffer from the soleoid failure actaully does do so, so don't be put off by this possible issue .I have also repaired a K-30 I was given with the same problem, and the same basic repair technique can be applied to any camera so afflicted.
Back to the K-S1, it is a delightful camera, and the results very good. If I had not needed a replacement very quickly after the aperture failure I would not have ended up with my KP, also a compact camera capable of truly excellent results, but nowhere near as light as the K-S1. Plus if your lenses have an aperture control ring, you can still continue using the camera pending a repair.