Vivitar Series 1 PF 383 Pen
Ok, this is what I have learned about the Vivitar Series 1 PF 383 Pen on the Pentax K7. I don't know if it is the same as the Sunpack or not.
Although the manual is less than helpful, it will do fill flash on automatic. In the past I have always used it on manual because that is what I am familiar with. I am not terrifically satisfied with all the results I got but it is not too bad.
I set the flash at TTL, which according to the manual will interface with the Pentax P-TTL system. I set the camera on the Program mode. I then used the camera and set a -1.3 exposure compensation for the flash by using the camera flash controls. I took several pictures of myself at arms length in the afternoon, both in the shade and in the sunlight. The flash worked perfectly every time and the power level was appropriate. I then reduced the compensation further to - 2, and again it worked as it should, the power was visibly reduced both to my eyes, and to the results.
The shadows under the brim of my ball cap were alleviated in both circumstances. However, and this is where I still need to do some more work, the exposure to the sunlit,lower part of my face is definitely over exposed.
However, at this point I can state that the Vivitar PF 383 Pen does do fill flash automatically. As I said, it may take a bit more playing to get it where you want, but it will work.
Obviously I cannot say that the K5, or the 385HV, will work identically because I am unable to test that combination.
You will pardon my not posting the images right now as they probably are not fit for human consumption.