Originally posted by indianswift will DA 50mm be a good investmentor
I think so. Maybe you would prefer the DFA 50mm f2.8 macro in case you want to do product photo photography (macro lenses tend to be even sharper, with a very clinical look, which makes them well-suited for product photos and closeups). But it really depends on what kind of studio photography you will be doing. If you want portraiture, the DA 50mm f1.8 is an okay place to start, and the DA* 55mm f1.4 is the higher end for portraiture (along with FA 77mm ltd).
Keep in mind that for studios, there are many other important things to consider, like lights, backgrounds.. and space. If the studio is small, then you will have a hard time using, for example, 135mm lenses for portraits.
And the lenses that you already have should be okay for the workshop. I think for workshops they usually take care of lighting for you (and teach you how to do it). Try the 35mm, and if its FoV is too restrictive, try the zoom. A good thing with the Pentax system is that the gear is fairly compact, so you can bring along a couple lenses without trouble. They will probably teach you what aperture to use, White Balance settings, and Exposure compensation (EV +/-). And of course how to position yourself