Originally posted by c.a.m A relevant and timely question, @Oakland Rob.
It would be useful if respondents could also give an impression of the lenses they use(d) with the K-3/K-3 II and with the K-1. I'm a K-3 II user, and one of my main concerns is the added weight and bulk that a K-1 combo would bring. I use a DA*50-135 frequently and a DA* 300 on nature hikes. I did have an opportunity to try a K-1 + D-FA 70-200, which struck me as a bit of a beastly combination for long hikes. Using smaller lenses wouldn't be so much of a problem for me.
- Craig
When I carried my K-3 I used a 16-85 a lot of the time. Naturally there are several primes I use too. The usual suspects are my primes. FA Limited and a manual fast 50. I carried my K-3 around the world at least twice. Maybe more than that.
The weight issue I don't think is that big of a deal. The only time weight will be an issue is for carry on luggage concerns. For a fully kitted out system it will be over the limit for a lot of carriers, especially little puddle jumper flights. Walking around I carry with a shoulder sling and I can carry a K-1 around all day without a problem. That said put on a huge heavy 70-200 or something giant like the 15-30 and no matter what you carry body wise it will be unwieldy over time. The shoulder strap is the way to go for walking around IMO. Makes all the size and weight questions moot for that aspect.
As for lenses and all that you will get substantially better low light performance out of the K-1. I use a 24-70 as my zoom choice, which basically gives up a little bit of reach on the long end in favor of constant aperture and substantially better low light performance. My primes amaze me. You can shoot in really really low light with the K-1 because of it's better ISO. Now add better ISO capabilities and fast lenses and you can open up a lot of worlds.
For example I was shooting in the moonlight one night as a test. I can do that with the K-1 whereas with the K-3 not so much. The bigger sensor just kicks everything up a few notches.
My main complaint about the K-1 is a lack of wide fast primes, but hopefully that gets fixed eventually.
I upgraded to full frame specifically because of better low light capabilities across the board.
See the pic below. I shot this walking around Shanghai at night and did it hand held. You would struggle to do this with a K-3 and almost any lens combo.