Originally posted by aju3169 I have the older Sigma 70-200 F2.8 APO DG EX - works perfectly with the K1 and my k5 II. It is very fast focusing on both cameras although no HSM. It has very good user reviews and might be an option for those wanting this zoom range and aperture. It's a bit cheaper too if you can find one on the second hand market.
Correction: Actually have the oldest version, i.e., Sigma 70-200 F2.8 APO EX (not DG). As already mentioned - it works perfectly with K1 and suprisingly very fast AF speed given it is a screwdrive. NO scratching of K1 body - the mount flange outer diameter is 60.0mm. I heard the the HSM version was measured to 63.5mm - hence the problem with body scratching.
---------- Post added 05-12-16 at 12:04 PM ----------
I have been testing my Pentax DA 1.4X AW rear converter
http://https://www.pentaxforums.com/lensreviews/hd-pentax-da-14x-aw-rear-converter.html. All my tests have shown that it is full frame compatible with the K1 although the camera will set it to crop mode if set to auto crop so you will need to set crop mode to FF. These are the list of FF lenses that I have tested it with:
PRIMES:
Vivitar 13/2.8,
FA 20/2.8,
Tamron adaptall-2 28/2.5 PKA,
FA 31/1.8,
SMC DA 35/2.8 macro,
HD DA 40/2.8,
FA 43/1.9,
A50/1.2,
A50/2.0,
FA 50/1.4,
DFA 50/2.8 macro,
FA 77/1.8,
DFA 100/2.8 macro WR,
Vivitar series 1 A105/2.5 macro.
Zooms:
Sigma 70-200/2.8 APO EX,
F 35-70/3.5-4.5,
FA 24-90/3.5-4.5,
F 35-80/4-5.6,
Sigma 28-80/3.5-5.6,
NOTE: the SMC DA 35/2.8 macro is FF compatible (not sure on the edge focus) - just don't fully extend the built-in adjustable hood to avoid vignetting.