I think most people have said what I agree is best... to wait until this new camera comes out. It looks quite the jump in technology! and we hope that it will be well worth the full-price. However, I think the way that Pentax appears to release cameras, is the first camera represents a big leap in tech (I think this feels like the significant leap felt from the K-5 to K-3, maybe even moreso)... and then they just funnel that tech to their 'budget' (ex: k-70), 'full-frame' (k-1), and then 'misc' (kp). Whenever someone asks me which type of (Pentax specifically) camera they should buy, I almost always start them out with the K-3. Are the improvements from the K-3ii, k-70, k-1, kp... really that different in terms of IQ? In some ways yes, but only incrementally and FF being what it is.
Having both a K-3 and K-1 (I actually picked up the K-3 afterwards) I can tell you that there is a pretty big bump up in IQ, as well as situations where you really feel the improvements play themselves out. There's the obvious 36MP jump up, which really any APS-C really can't overcome that part, and Pixelshift shouldn't be understated (I think the 3rd wheel is pretty big in terms of handling too)... but then there's the low-light performance where it truly shines. There are circumstances where the K-1 can take clear and 100% useable photos to the point where you'd never know that it was taken when it was. The dynamic range is impressive, but so is the way for it to manage noise as well. I always point to this video, when I reflect on the amazing range it has (3min):
However, there are places/circumstances where even the old K-3 has a big advantage over the K-1. The only real shortcoming in the K-1 imo, is the RAW buffer and 4fps. The K-1 will fill up after a handful of pictures, while the K-3 will shoot RAW photos for days and at 7fps. You really feel it during moments that are fast-paced like sports or events (I take pictures for my school sometimes) Also, you do miss the 1.5 crop factor in some instances. Using the K-1 you do have to re-adjust to taking that step back, but moving back to APS-C and its basically like putting a teleconverter on your FF-lenses. Also, one thing I didn't consider at the time that I made the jump, is that I would have to basically replace all of my lenses. It is shooting with the K-3 that has convinced me that there is value in having both. APS-C for events and speed (that 1.5 reach really comes in handy!), FF for when you need the added detail.
Originally posted by BlakeShellman Will there be any shortcomings for not using a lens designed for the K-1?
A lot of times I find that most DA/APS-C lenses can actually still 100% be used in 1:1-mode, which gives ~24mps. That's pretty useful!
I think you should just wait though, as many of the advantages in low-light are pretty negligible now with the new cameras. I got a KP for my sister-in-law, and sometimes I envy at it's low-light ability, and the newer cameras have Pixel-shift too. I think you should wait for this next APS-C camera. We've seen it, so it seems like its pretty far along. My guess is that Full-frame with similar tech will come right after that. It would suck to buy a K-1 now, and then the FF come out 2-4 years from now with the vastly new tech. Then if you still wanted to go with the K-1, it be cheaper... but in the meantime new APS-C would mean not having to worry about lenses too. Sadly, with the state of the world, this timeline might shift a bit in terms of waiting.