Originally posted by Aegon Another consideration is that Pentax's DA line is designed for APS-C and, in most cases, does not cover FF. Whereas many of the bright primes for Nikon/Canon are FX/EF and are generally correspondingly bigger.
Umm, that's a lot of jargon. Pentax lenses are mostly designed to cover a smaller sensor size.
This is one of the worlds biggest lies, that full frame lenses are bigger and heavier than APS-c lenses. Just look at Pentax, the DA 300/4 is an APS-c lens but is heavier than the K300/4 and substantially heavier than the M or A 300/4. And a whole lot bigger too!
Especially for tele lenses there are only really three main things that determine the size and weight
- aperture, F4 on 300 mm requires a front element diameter of 75mm after aperture = focal length / diameter
- lens mount diameter. The K mount is the K mount, it has a physical size, regardless of what is inside it, the lens barrel size at the mount must be , as a minimum the mount diameter
- optical/mechanical design. Optical design elements and groups plus correction for aberration all add weight, telephoto factor, and by this I mean the amount of physical length reduction by adding lens groups , to achieve the apparent focal length adds weight but duces length. (Remember telephoto does to mean more than normal, but lenses which are physically shorter than the focal length as indicated by the apparent magnification) . As others have noted, mechanical design, integrated motors, integrated automatic aperture controlled in lens electronically (canon) integrated OS all add size and weight.
Although Pentax may be much lighter and compact compared to canikon, many of their current offerings are still heavier than past ones.