Originally posted by CarlJF Exactly. For the same aperture, m43 will have more depth of field which will give the impression of an overall sharper picture, for better or worse. The correct point of comparison would be to use the 16-45 at f8. Unless defective, it should be very good at this aperture. At f4, some parts could be out of the DoF sharpness zone, which is to be expected if not wanted.
Or as I've often pointed out, the larger the format, the more expensive the gear, the harder it is to use. If you are happy with cheaper gear, there are many ways to achieve that. If you aren't maximizing the use of your larger format gear, then something like m4/3 might be right up your alley. The only reason for using a DSLR in my mind is those images you can't take with a smaller set up. If you can shoot ƒ8 you can get 4/3 cameras that you can print up to 30x40 with. Almost no one needs better. What APS-c and FF do well is narrow depth of field, and less noise with low light. My 1:1.2 sensor camera can really only be used to ƒ4 without diffraction, and I prefer only 100 or 200 ISO. The range of useful f-stops is limited by diffraction. If you want to do this, you need a 300mm lens at ƒ2.8 on DSLRs will handle at minimum ISO 100-1600, 6400 for my K-1.
If you want this you want a larger format camera.
K-1 and Tamron 300 2.8 @ ƒ2.8. 1/800s, 100 ISO
If this is good enough then a smaller format will do.
K-3 DA 55-300 @300mm ISO 100, ƒ10, 1/800s
The larger format gives you a choice. You can do either, with 4/3 you're likely only going to get the second one. But if you're saying "at ƒ8 they are pretty much the same", that's true. And if you only want the ƒ8 images, why even buy APS-c or FF?
So the current strategy is to build lenses that anyone can do what they want with regardless of their style of shooting. For those who want less, there's legacy glass. But it's not surprising that Pentax went with "do everything" lenses first. I'm sure they'll get around to more specialized lenses later, like the coming 70-200 ƒ4.
There's not a lot of legacy glass that isn't pretty good at ƒ8.