Did you know that an excellent DA18-55 lens usually shipped with Pentax DSLR cameras has very good close-up capability?
With minimum focusing distance of 0.25m (0.82ft) and at 55mm setting you could have a subject as small as 1.5x2.5" fill the frame? Perhaps DA18-55 is all you need? (And with camera it costs around $80.)
P.S. I see now that you have both DA18-55 and DA50-200. Consider then getting 52mm +1/2/4 close-up lens set for DA50-200. I am currently experimenting with that setup and at 200mm with +1 CU and 1.1m focus you can have 1.25x2" subject fill the frame.
But keep in mind the following:
1) Once mounted as filters close-up lenses prevent your lens from focusing beyond filter focal length, so you get macro-only and loose infinity until you remove close-up lens.
2) Dedicated close-up lenses (such as D-FA 100mm Macro) provide better quality, but at much higher price.
3) To avoid lens aberrations (especially CA) it is recommended to use f/8 or smaller apertures (f/11 or f/16). That may require flash or studio lighting.
Search eBay and on-line stores for "52mm close-up" for more details and prices.
Last edited by Ivan Glisin; 11-30-2006 at 02:42 PM.