Bonhour Nelepl,
Quote:
Pentax DFA 100 mm f2.8 Macro
Unfortunately, I have no experience with this lens.
Keep in mind a 100mm gives 150mm with a dSLR. Even for lens dedicated to dSLR, the old focal distance for film cameras (36 x 24 mm) is used. Since the sensor is smaller on a dSLR (23.4 x 15.6 mm), a 1.5 multiplier applies between focal distance for film cameras and focal distance for digital cameras. So, basically, you're going to have a tele-objective.
You may find useful information on
photozone, which is very interesting but rather technical. Here their
Pentax SMC-FA 100mm f/2.8 macro - Review / Lab Test Report, .
For a more user friendly approach, have a look a the many threads available in CamerLabs and, if necesary, open a new specific thread asking for feed-back on the Pentax DFA 100 mm f2.8 Macro
Fixed lens are said to be stronger than zoom, because there are no moving parts. The really nice aspect with a dSLR, you can add new lenses as you go and can afford

So that's a good strategy.
Good luck

_________________
--- rei_vilo
Pentax K-5 + BG4 + DA* 16-50 + DA* 50-135 + DA* 60-250 + AF-540FGZ
reivilophotography.weebly.com