k10 d focus

ok my sigma 28-300mm is working well and so is my 18-55mm pentax kit lens

know my new 55-300mm f4-5.6 will focus but after focus if i turn the focus ring (so it's out of focus along way say infinity ) it will only focus again some time and will fire when it's out of focus

any advice as I'm ready to throw it at the wall

Ps
this is all done on a t-pod and remote

James

Thank you John
I think you are right the sigma hasn't got this function as the focusing ring is solid

regards James

Agreed... however,
Not with my K10D.

With the half-press held, the green in-focus hexagon remains, even when I've quick-shifted way out of focus.

The behaviour is the same with both my 18-55 (Mk1) and 55-300.

agreed

the behaviour is the same with my k10

James

Perhaps "may" would have been a better word?

Having now tried it several times, it appears that the behaviour in AF is different than in MF.

Set to MF, with half-press held, the hexagon appears and disappears as you turn the focus ring. As you'd expect, the shutter will release whether in focus or not.

Set to AF, it focuses, and then the green hexagon remains lit after quick-shifting. You can still release the shutter at any time after the initial focus confirmation.

This behaviour is the same whether you have the Custom Menu set to AF on half-press or not - if not, holding the AF button pressed has the same effect as keeping the shutter release half-pressed if it is.


Worth knowing about this difference, perhaps - it might be possible to disturb the focus unintentionally while half-pressed in AF, and think from the hexagon that it was still in focus when it isn't.

Is it the same with the K20D and K-7?

The thing that's rarely mentioned is our eyes.

It may well be that many people are no longer used to seeing through a viewfinder. I know I've handed cameras to people before now and they've talken a look and said "I can't see through that" before rejecting it and passing it back.

When I look through a SLR viewfinder I can see if it's in focus or not. Pressing the shutter release half way makes a lens snap into focus, and I look at the image rather than the green hexagon. In fact, as I think more about it, I never look for the green hexagon.

Do people generally find it difficult to see that the lens is in sharp focus?

I think the test is to switch to MF, focus manually, and then press the button. If the focus confirmation comes up straight away, you pass the test. If you have to turn it a little, you failed it.

I tried it a few times - passed a few times, failed a few times too.

I think I'm aware of the confirmation more than I actively look for it. The AF snaps in, occasionally does a fine adjustment if the light is bad, and I'm aware of it finishing. I think I use the aural as well as visual cues without really noticing them, unless it takes an inordinate length of times thinking about it, as of course it does sometimes in near darkness or with low-contrast targets.

I take pictures in semi-darkness quite a lot, at dance events. Manual focus without a split screen or focus confirmation would be hard.

That's very interesting as I tend to shoot under disco lights using manual focus. No split screen either...

I suppose it just goes to show that we're all different and do things in very different ways.

As long as we get the end result it doesn't really matter!

I use the bleep to confirm the the shot is in focus!

Are you saying that this is wrong and will give me a false indicator in that i am in/out of focus.

James

i always look in the view finder and then the screen to view my shot

No, not at all, quite the opposite in fact. We're just commenting on the different ways people do things. All of them are correct. If it works for you, then you're using the right method.

That is impressive. I've been very lucky with my eyesight (still no need for glasses even at my advanced age of {redacted}, and I've always had very good low light vision too. It's not as good as it was, but although it's still better than people a lot younger than I, manual focusing fast enough in very low light isn't as easy as I'd like.

Sadly, I probably can't blame the (edit: camera) lenses for my failures...

Like John, I hardly ever look at the green hexagon, and tend to use my eyes...

I've resisted buying a split prism screen, partly because of the price, but partly because of the effect that these are reported to have on metering (and I have enough trouble with that already!).

This raises another question, though. When setting up to take star trails, or a very dark scene, using bulb mode, it's very difficult to confirm focus. On some of my lenses, infinity doesn't mean infinity, but somewhere beyond! (In other words, if I set the lens manually to infinity, I get OOF results, especially with telephoto lenses.) Any ideas?

For very low light focusing I illuminate the scene with my very bright LED torch. I have been known to use it as a light source for the image as well.

For star trails I'd just use the stars themselves as the point of focus - they will be sharper points when in focus.