This link is from a sticky in the lens subforum:
Pentax K-Mount Lenses Explained: The differences between various Pentax lens series. It explains the range of Pentax lenses.
Rena, you said you have the 18-55WR already and want to add a zoom. I'm not trying to be an ass but that is already a zoom. Assuming that you want a telephoto with more zoom, I heartily recommend the DA-L 55-300. It is a modern lens 100% compatible with the K7 and includes autofocus.
It is an outstanding lens for the price. You can currently get it for $200 new at Adorama. Here is the direct link
21897 Pentax SMC P-DAL 55-300mm f/4.0-5.8 ED Auto Focus Telephoto Zoom Lens, but please use the Adorama link that Adam has posted elsewhere so PentaxForums gets proper credit.
- The lens is grey market. Adorama rather than Pentax provides the warranty.
- The DA-L has more plastic than the regular DA. The build quality is still very good.
- The DA-L doesn't include a lens hood. The official Pentax hood costs around $45 extra. Or you can find an aftermarket hood on Ebay, or go with a generic screw-on collapsible rubber hood for ~$6.
You might find the DA-L 55-300 used for even less in the marketplace or at Ebay.
P.S. I just noticed you are in Canada. Not sure if ordering from Adorama in the U.S. hits you with exorbitant shipping or customs fees. I think ProDigital 2000's store on Ebay is based in Canada if that helps.