Originally posted by pres589 A 12-28 full frame lens would be massive compared to a crop lens, same max aperture to same max aperture. I don't know that you'd want to tell a guy that he shouldn't expect something non-massive when there's the DA15 also sitting there on the shelf.
Something like an 18-35 f3.5-5.6 full frame might be really nice for crop guys as well, to take advantage of the center sharpness extending over more of his/her crop sensor's image circle. It would also give a nice wide angle option for folks that know they're going to give up some quality in the name of cost, weight, and size advantage. Seems like a nice product for someone that wants to shoot landscapes with their K-1 but doesn't want to buy or carry the 15-30 DFA.
The DFA 28-105 lens is about the same size as my 18-135, My FA-J 18-35 4-5.6 FF lens is one of the lightest lenses I own. There is absolutely no reason an 18-35 4-5.6 landscape lens couldn't be as light and high quality as any lens out there. Just going ƒ4 instead of ƒ2.8 cuts the weight in half just right there. The 28-105 doesn't give up anything to anybody, for IQ at 5.6 (APS-c) or ƒ8 on full frame. There's no reason an 18-35 couldn't be built the same way. Lots of LD and Aspherical elements, they don't have to be large.
My FA-J 18-35 4-5.6 weighs 218 grams with the front and back caps on it.. They could double the weight for improvements and still have a manageable lens. The 15-30 weighs 1040. Even doubling the weight of the FA-J 18-35, you'd still save 600 grams or a pound and a a third over a D FA 15-30. Anyone who loved the 12-24 on APS-c should be clamouring for an 18-35 ƒ4-5,6. The 12-24 is 418 grams... if anything a lens going to 18-35 mm should be smaller. Even if it appeals to only those of us who prefer the 28-105 over the 15-30 , 24-70, 70 -200 combo (two lenses to cover the range of one lens), even an 18-28 would be acceptable if the weight could be kept down.
Variable aperture doesn't mean lower image quality. It means more flexible design constraints, better (more efficient) use of the front element of the lens. They are cheaper in price, not necessarily in IQ. A fixed aperture zoom is by definition an inefficient use of the front element, for all but the longer focal lengths. At least with variable aperture, you get to use some of that front element on your wider angle images.
I rest my case.