Olympus E-620 with 14-42mm f3.5-5.6 brand_Sigma clean optics (with minor dust)

clean optics (with minor dust) and excellent function

but it's secure and easy to use

Energizer Ultimate Lithium batteries are long-lasting

No effect on function- it's cosmetic

The Pentax 645Z is a digital medium format (33x44mm) camera with a 51mp sensor

Olympus E-620 with 14-42mm f3.5-5.6 brand_Sigma clean optics (with minor dust)Just to get it out of the way up front, the Olympus E 620 is a Four Thirds format DSLR, not a Micro Four Thirds mirrorless camera. It's compatible with Four Thirds SLR lenses, not Micro Four Thirds lenses, and it has a real optical viewfinder rather than an EVF. It's still a reasonably compact camera, though, and still packs a tilt swivel screen and an in body stabilizer. It's got a 12mp sensor, built in flash, and a pretty good live view system, too.