Originally posted by Dan Rentea Oh, this is a tough subject... Most of the time when people talk about wildlife, they usually talk about stationary subjects. For this kind of wildlife any kind of camera released these days can do the job.
Regarding K-3 II and DA* 300mm f4 lens, it's a very good combo for stationary subjects. That lens is very sharp, but is very slow to focus if you want some consistency, at least to me.
Regarding K-3 II and D-FA 150-450mm, I didn't get the chance to use it for BIF and I don't know how good it is. I've used it for some stationary subjects and it seems fast to focus compared to DA* 300mm.
Regarding D500 with Nikon 300mm f4, you can't find a better camera for BIF in this price range. With a 1.4x TC and you will have 630mm at f5.6.
Regarding D500 wtih Nikon 200-500mm f5.6, for tracking in my opinion you will get better results than you will get with K-3 II and any zoom lens. Af algorithm is better on D500, af points are spreaded almost all over the sensor, you get 2 aditional fps...
I use Canon, not Nikon, but I shoot as much as I can with lots of cameras from different manufacturers. When I'm really after a subject, I rent Canon 300mm f2.8L lens and if I need more reach, I have with me a 1.4x TC or a 2x TC. If you find a prime lens like 300mm f2.8 (or 300mm f4), 500mm f4 second hand at a good price, go for it. It will make your camera to shine. These lenses are good because can be used handheld if necesary.
K1 can be problematic for action. It's not designed for this job. Again, for stationary subjects can do the job and you'll get beautiful files.
Find a way to rent first a Pentax 150-450mm and see if it is going to do the job on K-3 II. To me, if you are a photographer oriented on action shots, Nikon D500 is the better option. If by wildlife you mean birds sitting on branches, animals walking in the forest, then a fast lens may be enough to keep you satisfied.
What he said/^
Paying thousands for a lens you've never actually used is insanity. And paying for capability you'll never use is equally insane, Where I live, with our wooded hills and dense forest, the opportunity for BiF photgraphy rarely arises. Pentax's superior AF.s is worth more to me than anyone's tracking AF.c. But if you are really into and have opportunity to catch birds in wide open spaces from view points that let you track them, something like a D500 is a no brainer, and a k-3 or K-1 can be really frustrating. You just have to be comfortable with the cost, and lack of resolution. When I nail a K-1 image it's better than a D500 image, but, I may miss the shot altogether if it's bird in flight. Not at all for landscape, wildlife, perched birds, or most of what I shoot. But if all you do is BiFs, or action sports, anything where AF.c is an advantage, maybe you'll put up with second rate resolution and slower focus confirmation for first rate action shots.
I have an opportunity for BiF images maybe 4 times a year. I shoot macro, landscape, flowers, stationary birds, forest walks, mushrooms, sunsets, waterfalls, etc. more often. For me the choice was simple. A camera for 95% of what I do, make do with the other 5%. Because for the other 5%, I rarely get nothing, I just don't get as much. On the other hand, for 95% of what I do, a D500 isn't the better camera.
Like my K-3, if I had a D500 I'd still want my K-1 for most of my shooting. But adding a D500 in place of my K-3 would be an upgrade. If you are considering a K-1, in most ways either a K-3 of a D500 is step back. Just the K-3 is a bigger step back with less to offer, and that's reflected in the price.
It almost always comes down to how much is it worth to you? The only all purpose camera for me would be a Nikon D850, and I don't want the expense, so, that's not going to happen.