Originally posted by no694terry I got back into Pentax with a K3 18-135 kit. Love the lens but I'd like some better results. I was thinking a Pentax 16-50 or Sigma 17-50. For wider angle and little more speed. I had a Tamron 17-50 before and i liked the 17mm over 18mm, the F2.8 was nice too
And then adding a Sigma 50-500 non-OS for outdoors (i'm not rich).
What yinz think?
1) The Tamron 17-50mm is a winner in my book for price/performance. Photozone.de gave it nice ratings. There are several great options in that range, and you already know about them. They all have advantages and disadvantages. You cannot lose with any of them.
2) The real question is on the long end. If you are not shooting sports or moving wildlife, consider a couple of quality but older manual lenses. These lenses should be sharper than the Bigma you are considering. If you had more money, I'd suggest the Pentax D* 60-250mm and a tele-extender over the Sigma offerings. Since money is an object, one of the Sigma super-telephoto zooms will make the most sense. Consider buying one used, provided the seller has a return policy. As we all know, lenses drop in value as soon as they are sold (like cars). Getting a good used copy saves $ and allows you to get better glass for your money assuming you get a good copy. Over the years I had to return two "bargains" purchased on ebay because they had issues, but both sellers issued a full refund.
3) If you really want what the title of this thread requested--turning two lenses into one--consider doing more: turning whatever you purchase into multiple lenses (or "one" with a really massive range). Consider buying an inexpensive prime or two and making macros out of them using a $4 reversing ring or cheap extension tubes. For example, the 50mm M 1.8 goes for $40-$50, is sharp as can be by itself, and can double for macro work with a reversing ring or extension tube. Consider a tele-converter too, but beware (and double beware): It is essentially a magnifying glass that will make the lens "slower" and magnify any imperfections. They work best at a magnification of 1.4x or 1.7x, and almost never at 2.0x or above (where you would be better off cropping).