Had a bit of a shock last night. I have this Tamron 28-75 f2.8 lens and i was manually focusing it on a magnetic advertising sign on my refrigerator, 25 feet away from my easy chair.
1. I used the OVF on the K3 and tried to focus it that way. Also noticed that the AF blip showed up when i was close to focus - not that i could tell at that distance. print on the advertising is too small for my eyes to read. When i played the image back and enlarged it 8 times, it wasn't close to being in focus.
2. I then switched to live view and even enlarged the live view by pressing on the OK button. I could see some focus peaking effects when i snapped the picture. I then played the image back as in 1, enlarged 8 times. Better than 1, but still a bit blurry.
3. I then transferred the K-mount Tamron lens to my Nex 6 via a $19 dumb adapter. Unlike my k3, there was no stabilization system active with the Tamron in manual lens mode on the Nex 6. I took a picture under the same parameters as with the K3, i.e. 1/160s, 1600iso, 75mm, and f4. (although on this adapter, one can't tell the f-stop precisely) Taking the shot with the Nex 6, the phone numbers on the magnetic sign were more defined than they were with the K3 image.
So my Nex 6 with the Tamron 28-75 f2.8 lens manually focuses better than the same lens on my K3. My K3 cost me about $1300 and the Nex 6, cost about $650. How do i explain this difference. Well the explanation that makes the most sense to me is that the Nex6 has an EVF, and when you manually focus, its easy to brace the EVF against your face while the K3 in Live View mode must be held out at 1/2 arms length. So therefore, the Nex6 is better braced when in manual mode. So an APS DSLR costing twice as much as my APS mirrorless loses out in manual handheld focus mode.
The K3 is an Auto-focusing monster, it just lacks a bit in the manual focus mode. Probably on a tripod, it might be just as good as the Nex 6, don't know - didn't test for that.
I shot a technical rehearsal last night of a new play with my K5 with the 50-135 tele on it, and the K3 with a 17-70 wide angle on it. First time with 2 cameras at hand. Enjoyed the OVFs of both as i waited for actors to get in just the right spots. Got enough keepers to make the director happy. It was autofocus for the whole 2 hours. So there are advantages to the traditional DSLRs, but i'm convinced the market tide is changing direction in favor of the mirrorless cams. Pentax would be ahead if they made a mirrorless FF, but rest assured, i get no vote in the matter