It's in the Bag - Vintage Pentax Glass on Modern Panasonic Electronics.
That led me to a prime lens, but which one. The DA21mm F3.2 would be a bit wide. The M50mm F1.7 would be a bit long and possibly move the camera-mounted mic farther than I wanted it. I ended up choosing an old Pentax M28mm F3.5 instead of the DA35mm F2.8 Macro Limited as I thought that the 28mm would give me the focal length I desired - a mix of subject and background.
One problem - the 28 had languished in a drawer for probably 15 years. Even when I jumped to Pentax dSLRs in 2009 with the K20d, it sat untouched as I was foolishly drawn to faster glass. But since I was shooting video solo and really couldn't spend time keeping focus locked, I decided to shoot at around F4 and hope the DOF would keep me sharp.
To make sure the lens still worked, I went into the backyard and took some test shots. I was pleasantly surprised with the result.
The lens draws nicely, with good contrast and colors and more than enough sharpness for 1080p video. For those scoring at home, 1080p is around 2 megapickles.
Things worked out great with the shoot. We found a picnic table in the shade. I cut down the light with a couple of Cokin filters (an ND and ND grad) and had a good conversation. The footage looks really nice.
Kudos Pentax for making such nice lenses 30+ years ago. And kudos Panasonic for making such a nice camera!