Originally posted by ElJamoquio 1) The Sigma and Tamron are APS-C only.
2) It is very likely that a Pentax FF would have a 'crop' mode to use older glass, and many of the DA lenses already cover FF. Things like the 35mm F/2.4, 40mm F/2.8 (XS is cheaper of course) and 50mm F/1.8 are inexpensive 'DA' lenses that will become very, very capable on FF.
3) Why do you want a F/2.8 on APS-C and also an F/2.8 on FF? You're comparing a far more capable lens on FF to a much less capable lens on APS-C. On the other hand there may never be a F/4 or F/4.5 FF zoom for Pentax, so who knows.
2) never heard of crop mode...
3)Far more capable 2.8 = paying more , much more..For example the mighty 16-50 2.8 from Pentax have two big disatvatages for me: price and somehow weight...Even if i get the 16-50 lens for free i still have a hard time carring it around..It's not about laziness, it's about handling heavy system..I need the element of spontaneity not imposing.Heavy equipment needs more care..So my mental limit is a K-5 body + 560grams lens added combo ...Even here i still have problems but is still fine..
Only the lens is 1000euros//1300$ -- That's beyond what i want to pay..
For example i wouldn't buy a Nikon D600 because weight of the body and here i am not discussing brand preference..So
Weight (inc. batteries) 850 g (1.87 lb / 29.98 oz) ... 760g without batteries
K-5
Weight • No battery: 670 g (1.4 lb)
• With battery: 750 g (1.6 lb)
It may not seem like much but for my skinny hands it makes a difference...When i jumped from K-x to K-5 i felt it...But the WR really is desirable for spontaneity...
Of course this thing with weight is my personal specific problem...It is somehow my standard ..You guys have other physical bodies and you have other standards...Your hands may handle easily 1kg body only ...