Originally posted by gybp Hi, i actually have these lenses,
50mm f1.7, 50mm f1.2, 28mm 2.8, 18-55 kit lens, 70-210 f3.5
as you see i have no macro (actually i have a 90mm tamron macro but for my nikon camera that i dont use that often)...
First, the Nikon (Tamron) macro lens may work on the Pentax camera (without automatic functions) - try it.
Second, the magnification one can get with one lens reversed on another is about
:
Magnification=Focal_length_Primary/Focal_length_reversed
So for your lenses some of the practical magnifications are:
50/50 = 1x
50/28 =1.8x
(18-55)/28 = 0.6x - 2x
It is important that the reversed lens have a way for you to manually control its aperture (although it is not difficult to find a kludge solution if necessary.)
The first two lens combinations are essentially restricted to only the magnifications shown so aren't very versatile; the 28mm lens reversed on the kit zoom would give a nice range of magnifications and preserve all the automatic functions of the kit lens....the working distance would be small but usable - greater than a couple inches.
You might consider getting a $50 Raynox DCR 150 to put on your 70-210 zoom...it'd give you a nice working range & high image quality.
Lastly, consider reversing the 28mm lens directly to the camera body - this would typically give a magnification of around 1:1 and likely be of higher optical quality than any of the combined lens approaches, but would be strictly manual.
Maybe you should buy a lens-lens ring to reverse your 28mm on your kit zoom AND a ring to reverse the 28mm directly to the camera. This would give you some versatility at not much cost.