Part of the dilemma is driven by this shot which I took at Whitby, and really like the effect.
For this shot, I used the K1 with a Samyang 8mm, which is a crop sensor lens so doesn't fill the frame and only uses about 17Mp of which this is a 12Mp crop
Orkney in particular may offer spectacular big sky shots, and I could use the Samyang 8mm f3.5 on the A6300 (and get 24Mp images) or a very large and heavy 15-30mm f2.8 ED Pentax lens on the 36Mp K1, or even take the 8mm with the K1 and its standard 28-105mm f3.5-4.5 ED lens.
Here come several images I used to try to resolve the issue: All images have identical post processing settings and are at f/8.
Pentax K1 and ED 15-30mm @15mm
Pentax K1 and ED 28-105mm @28mm
I was surprised by how much wider the Samyang appears given that used on the Sony it would be a 12mm full frame equivalent.
Despite the noticeable distortion at the edges of both wide angle lenses, IQ is high in all images. Lens corrections improve the barrel distortion of the fisheye Samyang more than the slight pincushioning of the Pentax. I also find the fisheye more natural looking.
If I try serious pixel peeping on these images (0.6Mp central crops), all images still stand up well, but the quality of the Pentax combination is outstanding.
Samyang/Sony
Pentax/Pentax
The last picture is a tighter crop on the Sony/Samyang combo to match the Pentax crop. Pixellation is starting to appear at this magnification
Here finally is a crop into the 28-105mm image (@28mm). Again the ED glass has produced a great image.
So, the decision ?
Much as I like using the Sony, I really can't justify NOT taking the Pentax K1 and both ED lenses in my camera bag so I will have to man up and carry the weight. The 8mm lens is small and light enough to slip into a suitcase in case I feel the need.
