Originally posted by roberts_camera I am going to wait until the new camera is released to make my decision as many of you suggested.
Congrats to come to a conclusion despite the diverging advice. As long as the K-50 works reliably, it's definitely a viable and arguably a good one in terms of sustainability.
I'd nevertheless like to add some thoughts/experiences, maybe interesting to others: I'm using both a K-1 and a KP currently myself and post-processed a lot of pictures from my daughter's K-50. Several of them from trips, where I used a K-5 or K-1 at the same time.
From a raw image quality perspective, both K-1 and KP provide substantially more detail than the K-50 - you sure will have noticed that when renting the KP. The difference between KP and K-1 is much smaller, despite another 50% of pixels on top, because quite some of the detail in the K-50 is lost in the AA filter. In terms of dynamic range, the K-50 isn't bad at all, but it's clearly where the K-1 with its large sensor really shines. There is a lot of shadow detail, which can be pulled up. I haven't used the KP long enough, but so far it seems to come pretty close if you compare equal amounts of light captured - not wanting to start an equivalence discussion here, but think of similarly big lenses for both, which of course are not always available.
Handling-wise, with a bit of routine and customization, both cameras are quick to use and handle well. Compact/lightweight lenses, such as an FA35/2.0 (or the DA 35LTD) as a normal prime, the 15mm LDT ultra-wide, the often underrated compact and lightweight HD DA 18-50mm as standard zoom, any of the old-style 50mm lenses (F50/1.7 or 1.4, DA50/1.8), the still compact FA77mm, DFA 100mm macro and even the still lightweight 18-135mm and 55-300mm PLM handle on the KP really well. I'm using the 'large' grip and while it only covers 3 fingers plus the pinkie halfway below the camera, I feel confident with it. Other than those, I have used the Sigma 70-200mm/2.8, and that one feels
a lot better with the grip. The K-1 in contrast feels glued in as soon as I take it into my hand, with any size of lens. No need for a grip, which would make it even heavier than it is. When I bought the KP, my plan was to use it for slightly other purposes/advantages than it turned out to be: The higher pixel density promised more detail for macros and less fatigue in my hand than from the heavy K-1, alas I underestimated the difference in handling that the K-1 display makes. The ability to arbitrarily tilt it allows me to reach better angles when using live view, and - to my aging eyes - the 10% extra height of the K-1 display makes a surprising difference. The K-1 viewfinder has a significantly wider angle of view, which is not always an advantage when wearing glasses. I tend to compose differently with both cameras. For another potential application, photographing sports on the field (more reach), I'm still torn between the KP and K-1. The later gets used in crop mode, which provides some nice context around the frame in the viewfinder, whereas the KP has a little more crop potential for far-away shots. Frame rates are similar (in crop), buffer is deeper in the K-1, but I haven't hit the limit on the KP the way I shoot. In the gym, every bit of extra light counts, the K-1 it is.
I always need to remember to pack fresh extra batteries for the KP, the higher processing power seems to eat up the LI109s even quicker than in the K50.
Despite my unmet expectations, the KP is far from being a disappointment. One reason are the out of camera JPGs. The combined Pentax/Ricoh expertise seems to show - while the GRIII seems to still have an edge, the KP offers a lot already. I usually shoot DNG+JPG and I find that with the KP, I have am much higher rate of JPG images than from the K-1, for which I don't even bother to pull up the DNG. The KP has quickly become my camera of choice for trips, where space and/or weight are important: A kayak trip (2w), a bicyle trip (1w), numerous business trips, where it made it much easier to stay within the 8kg carry-on limit. With the compact lenses, it also draws a lot less attention in the streets. I'm happy to carry it on a PD capture clip, nothing I'd do with my K-1. My K-1 on the other hand will continue to be my first choice for hunting bees, any night/astro shots, trips where photography is a primary planned activity and in general when I plan to use a tripod anyway. Even for full-day hikes, when I carry a backpack anyway, it's my first choice.
So back to the original question: The KP is a huge step up from the K-50 and has its own advantages over the K-1. Unless there are aspirations in fairly specific areas, the KP would be a
much more economic choice, reusing lenses such as your very fine 50-135 star and batteries. For me, I even bought two additional APS-C lenses and I'm holding on to others, which I planned to sell, because I really enjoy using the KP. Much to the delight of my daughter, who likes borrowing the lenses as her K-50 is still going strong and frequently produces better pictures than my cameras combined - the most important factor is still behind the camera. So get what makes you happy and inspires and it will likely show.