Originally posted by discharged I thought the reviews that compared it to FA 300 or DA 300, was exaggerated, but now I am not that sure any more. This lens will better any 70-200 F2.8 I could have gotten, Sure, I lose 1 stop of light but I gain 100mm on the long end. Also I will get nice biceps with the weight of the thing!
Very good choice and congratulations! I have the same lens and it is absolutely stellar on my K-30, so I can't wait to try it on a K-1. And f4 is surprisingly useful even on my APS-C camera, so on a K-1 it will be even more so.
I made the same lens recommendation to someone last week in another thread who was pondering which 70-200mm to get for his K-1. Like I told him, the 100-300mm is like having a 70-200mm with a teleconverter built in, but without any of the size or image-quality tradeoffs that a TC involves. So I strongly agree that the extra 100mm is well worth sacrificing f/2.8.
It looks like there is still another 100-300mm f4 for sale in the Marketplace for some other lucky K-1 owner:
https://www.pentaxforums.com/forums/24-photographic-equipment-sale/315204-sal...-300-f4-2.html