Several good solutions are suggested above, but I will add my two-cent's worth anyway. You were not very specific about what you mean by "close up". In general, that means 1:2 to 1:5 reproduction ratio. True macro generally starts at 1:1. If you are mostly interested in close-ups (action figures, flowers, toys, etc.), most good zoom or prime lenses with close focus capability will do quite nicely.
Close-focus Examples:- Tamron SP 35-80 (mentioned above)
- Volna-9 50/2.8 (Yes, it is Russian...1:2 with great image qualities...and did I mention that it is cheap? See Volna Posting)
- Vivitar 28/2.8 CF (On APS-C, it is one of the better near-macro lenses that you can buy. See Vivitar 28/2.8 CF Reviews)
If you have the occasional need to go smaller, adding the Raynox to your close-focus lens is a super solution.
Edit: I just checked some current pricing on the Volna-9. Apparently the word is out about this lens and it is no longer dirt cheap.
If you are sure that you are wanting to photograph the truly tiny stuff and get great results, here are some of the cheaper options:
Cheap True Macro Options:- Older manual focus macro lenses (M42 and K-mount)
- Raynox (again)
- Reversing ring + 50mm lens (the absolute cheapest)
- Extension tubes + 50mm lens (the next cheapest...think Volna...)
- Bellows + 50mm lens (a little more money, but you can get some really incredible magnifications)
If you are considering an older macro lens, don't be put off by brands other than Pentax or by the lack of autofocus or need for an M42 adapter. Almost all dedicated macro lenses do an excellent job.
A few other things you might need for high magnifications:
- Tripod (Hard to do macro without one unless you have a good flash setup)
- Good flash setup (Really nice to have even if you have a tripod)
- Focus Rail (Used with tripod...in the macro range it is easier to move the whole camera to focus.)
Steve
(Uses a dedicated macro lens, bellows, and/or reversing ring...still needs good flash setup...)