Again becuase I am at work and on my cell phone at the moment, my response will be brief. The 55mm is a good to very good lens but I found sample to sample variation and many have side's and corners that lag behind central resolution until well stopped down. Some had edges that never quite caught up to center sharpness. The lens is WR and is certainly light enough and focuses quite fast but personally its not my very favorite.Dave, thanks so much for your work in testing out the various lenses for the Pentax and also for your comments here.
No, this is not my first trip and hopefully not the last either
Do you think the 45-85 is a better choice than the 55 - I ask from the weight point of view and some reports that the zoom is soft at longer end.
I think as my experience with the 645 grows I will become more confident in its use as my primary camera, but I am a bit far from that right now. So the Canon system will definitely see quite a bit of use on this trip.
Pradeep
By contrast a excellent sample of the 45-85 has turned out a most useful lens amd optically very good to excellent especially between 45-65mm even when shot wide open. At these more open apertures, the 85mm focal length is softer in comparison but still decent and once stopped down a bit more comes close to the rest of the zoom range. All this is predicated on both a good sample as well as adjusting given lens for front/back focusing thru the 645z menu. (Fine tuning lens). This is important especially with this lens.
Bigger and considerably heavier than the 55mm and not WR, its a tradeoff but personally if it comes down to optics, I'd reach for the zoom. Many of my ley pages for professional jobs and very large format prints were taken with this lens.
Keep in mind I pixel peek at 100% of the entire frame and also often print crops of what would be very large prints before determining performance of a given lens.
Dave (D&A)