Don't get me wrong, the A7r is a stunning camera, as a regular on the "Talk E-mount" forum I posted quite a few photos and had the opportunity to see a a huge library of shots posted by other Sony users. Looking at the images posted led me to conclude that the A7r was probably the best of all the Sony cameras (yes, including the A7rii) closely followed by the old Nex7. Of course it could be that all the other users were not so good at post processing as A7r and Nex7 users but this is hardly likely. I also concluded that Canon lenses may well be the best, but as I don't have any that is a side issue. All my lenses except for one Russian 50mm f2 are on the Pentax K mount, and are mostly legacy manual lenses.
The old lenses worked very well on the A7r but a couple of more recent zooms by Sigma and Tamron (which I was still using on my Pentax K5) were not so good and new "FE" full frame E-mount lenses are very expensive. The lack of in-body image stabilisation (IBIS) was a slight downside, but reasonable high ISO performance helped to mitigate any problems by allowing higher shutter speeds. This also limits the impact of the rumoured "shutter shock" problem with the A7r.
The Pentax K1 was still hanging there on my wish list and having agonised over the cost for months, and seen how well it performs on the DxoMark testing (I use the DxO suite for almost all my PP), I finally part exchanged the A7r for a K1 toward the end of 2016. (Yes I know the A7rii is the best here, so lab tests MAY not entirely reflect "real world" results)
BTW Canon fans, if you are wondering where the Canons are, they start at 15th place
So is the Pentax K1 any good?
Yes! initial impressions are that it is very good. Compared to the Sony it is heavy and bulky, although it isn't a lot bigger than its APS-C siblings, the K5 and K7 (it is 200g heavier than the 5D Mk4 and 130g heavier than the D810 but with IBIS, the lenses will be lighter). The ergonomics are good with controls well placed although the buttons and knobs may not be quite as flexibly user defined as on the Sony. The Pentax body, and most of the modern lenses, are weather sealed so a small amount of rain won't hurt, although I wouldn't trust it in a real downpour.
I haven't really pushed it yet, but definition and depth of colour are excellent although, when used in aperture priority mode, images are overexposed for my taste and I tend to preset 0.7 stop of under exposure to maximise retention of highlight information. The 5 stop IBIS works with all the old manual lenses as well as more modern glass and really helps longer exposures.
The same system which moves the sensor for IBIS also operates the pixel shift system, taking 4 shots with the sensor shifted 1 pixel each time leading to a sample of each colour at every pixel location, like shooting 120Mp. The camera needs to be steady and with minimal movement in the image for this to work, but I will try it out when I have some large memory cards for the huge files it creates.
I believe 6 of the top 8 cameras in the DxO ranking use fundamentally the same sensor which is excellent. The Pentax high ISO performance is slightly better than the Sony with very little noise below ISO 12800 (max is ISO 204000).
So basicaly, it is great to be back to a Pentax based system again and the initial impressions of the K1 are very good, but I don't think I am quite ready to let go of E-mount. I enjoyed using my old Russian 50mm F2 lens (which is Leica mount and intended for a 35mm rangefinder camera) so I am looking out for a cheap Sony NEX on Ebay.
