The three axes we normally consider (x,y,z) only define the position of a point in space (in the case of a digital camera the one point that defines the center of the sensor). Since a camera sensor is not a point, we need to consider also rotation of the sensor around an axis vertically through the center of the sensor (this axis is parallel to the vertical sides of the sensor) as well as rotation around an axis that runs through the center of the lens. Rotation on either of these additional two axes will not move the center point of the sensor, while other points in the sensor do move.

If you prefer your ultrawide without fisheye effect, the Pentax 12-24mm f4 produces very nice images.

Having owned a '67 Goat, that's what I was thinking.

C and F with B added only if there is room. Keeping it simple while covering a wide range of focal lengths.

You might get more interest on PentaxForums.

I think there is also an element of "look where I am" or "look what I'm doing" to selfies. I don't need to have pictures of myself to prove (to who?) that I've been somewhere or done something I think is special. But then again, forums like this are the closest I get to social media.

And OpTech offers a system that lets you buy a neck strap and with a few additional pieces, convert it to a one shoulder sling strap and back again. Lots of flexibility and comfort.

Sounds like good advice. We did the Danube and my 17-50mm on APSc was my most used lens. On some of the city excursions I could have used something a little wider, but seldom had a need for longer.

Correct. And many EULAs (End User License Agreement) include a clause that the software author may revoke the "perpetual" license for specified reasons.

No electrical contacts, so manual everything - https://www.bhphotovideo.com/c/search?ci=276&fct=fct_camera-body-mount_65%7cpentax-k&origSearch=extension+tube&N=4077634539

Take a look at the Lowepro Tahoe BP150. I've used mine with body and a couple of lenses and accessories. If you arrange the internals properly the 70-200 may fit mounted on the body. There is a pocket that I can fit my 13" Dell XPS in, so a tablet should be no problem.
https://www.bhphotovideo.com/c/product/1163441-REG/lowepro_lp36892_tahoe_bp150_backpack_black.html/specs

Completely agree. I have found little to no use for longer zooms in city environs. For wider you can always brace yourself against something and take overlapping images to stitch together later. Enjoy the trip!

PS is no longer available for purchase as a standalone application, but only as part of a subscription. You may be able to get a copy of CS6 used, but licensing might be an issue with such a purchase.

Great image!

I have to add my recommendation of the Dell XPS series to the others that also recommend them. Since the XPS is available in both 13" and 15" versions, you should consider the tradeoff between screen size for ease of editing and portability. My 13" version fits in my smaller backpack, making it an easy carry on various flights. However, I don't do too much in Photoshop on it, reserving that for at home on my desktop.

Spec-wise, I have an i7, 16GB of ram and an SSD. You could get away with lesser processing speed and ram, but you might not have the patience for some of the filters, etc. in PS.

You should post this question on PentaxForums. More than one individual there does camera repairs and should be able to help. If you intend to use the camera, a CLA would probably be advisable, too.