The difference is that mine attaches to atapibus, and this one to scsibus
  (as my usb stick does). Why ?

I also have this issue with a pentax optio s4i; my other camera
attaches via scsibus.  I believe there are multiple ways that umass
devices can behave, and my experience, now quite old, was that NetBSD
only works with the scsibus way.

But, it's been months since I tried - I use an external card reader
(Sandisk 8-in-1, Sandisk CF reader) and that has worked well.

-- 
        Greg Troxel <gdt@ir.bbn.com>