In this illustration, compare digital camera sensor sizes: full frame 35mm, APS-C, Micro Four Thirds, 1-inch, 1/1.7″ and 1/2.5” Type. For new digital cameras, a bigger sensor area captures better quality, but requires larger diameter, bulkier lenses.
To optimize the size of a serious travel camera, consider 1-inch Type sensor or up to APS-C sensor size. “Full-frame 35mm” sensor / film size (36 x 24 mm) is a standard for comparison, with a diagonal field-of-view crop factor = 1.0 In comparison, a pocket camera’s 1/2.5” Type sensor crops the light gathering by 6.0x smaller diagonally (with a surface area 35 times smaller than full frame).