Not quite. What you are describing is optical flash. The flash on the camera controls the off camera unit by optical means (a third flash). There is no radio involved. However in situations where you want to use HSS, the scene you are photographing will be quite well lit with ambient light. This can present a problem for optical triggering as not only does the off camera flash need its optical receiver to be in sight of the on camera flash, but it needs to be getting a bright enough signal. If it is inside a softbox for example it will be very hit or miss. That is where radio triggers like the Cactus units come in.

It can. I have not used HSS a lot but have given it a try in the past. You will need two transceiver units (I use Cactus V6II). One on the camera and one on the flash.

If you later wanted to add another flash into the mix you could just buy a Cactus RF60X which has a receiver built in.

I like it, very artistic

Agree with the last two comments. That's what you get with a 1.2 lens

K1 + FA* 24mm f2

Nice work, I must try this sometime.

Two years ago we took a holiday cottage high up on Askham fell in the Lake District. The owner said "you will see plenty of red squirrels up here" He was right. There was a feeder opposite our front door. We were told in no uncertain terms to put anything out for them as he took care of it all. Every morning as we ate breakfast so did 3-5 red squirrels. Closest I have ever been, and didnt bother taking a long lens that trip so no photos unfortuately !

.....that only a mother could love

If I remember correctly, with any Pentax camera HSS is a P-TTL only mode, but you can use flash comp.

The pheasant for me too. Perhaps a bit of selective brightening on the bird to bring it out a little more ?