I'm asking this in the lens forum because this seems more lens than camera related. Maybe its a bit of both. I find that using focus lock confirmation with MF in low light (0-2EV) is not working well with both the A50 1.7 and M50 1.4 I have. They seem to consistently back focus. This is with the center point locked on a rather large target, like someone's face. I find the 18-55 locks well usually (when it get get enough light to the AF module in bad lighting that is). As does my tamron zoom with marginal light. I have a k-7 and upgraded to a k-5. The k-5 AF seems a bit faster to me, but nothing mind blowingly better. It does handle low light a bit better it seems esp around 0-1 EV. Still its so frustrating to go back and find the wall behind your subject perfectly in focus when you know it confirmed lock on their face or their jacket. I understand that its only a f5,6 sensor array, I get that. Thing is with a 1.4 lens it should be much easier for the lens to pick up focus. I don't get it. Can someone explain to me why fast primes want to lock on focus incorrectly? Is it the size of the focus point? I mean they are pretty big.
Usually what I do is back focus off and then refocus and do this a couple of times until it seems perfectly sure. Shoot. Chimp. Grumble. In street you need the damn shot. You don't have time to miss. So with MF, I use catch in focus and hold the AF button if I need to recompose. I'm typically shooting around f2-f2.8 these days in low light and when I want a fairly shallow DOF, so missing doesn't leave you with much to take home with. I hate that its always the wall immediately behind someone. Has anyone else noticed this? In good light these lenses are usually tack sharp when in focus and give reliable focus locks. I've never felt the need to adjust any of my cameras for focus, thought I probably should see if I could tune up my 12-24, but its already pretty sharp.
Was just hoping I'm not the only one that has had this problem.
ps forgive any typos or bad sentences if there are. I keep falling asleep (twice now lol) while writing this and am far too tired to proofread. Its been a long day and some good pictures were taken. Thanks pentaxians.