I have a RZ that came with the 110mm, wonderfully sharp lens but I don't think they make one for the RB. Predominately a landscape shooter, the next lenses I bought were the 50mm and the 65mm, gives me a choice of wide angles. Then I bought the 180mm.
The 90mm is exactly inbetween your 50 and 180. That, to me, makes it the logical choice if you are only looking at one more lens. But I would probably go for two more lensese to round out the outfit, the 65mm and 127mm. That way you would have a little more spread of focal lengths.
As far as macro, shooting my RZ with the 110 at full extension the other day, I could not get any where near enough to a pepper to fill the frame (I'm reading Weston's Daybooks so it was a homage to him). Just received from KEH a #1 extension tube (for a mere $29 that doesn't have a mark on it eventhough it was listed as BGN). Now I can fill the frame. Instead of the 90 or 127, you might want to look into the macro lens at that focal length.
Last edited by r-brian; 12-10-2010 at 10:49 AM. Click to view previous post history.