[davea66]

Hi

I have the above lens on my K-r, and it's a really versitile lens and produces some good images for my level of photography

However if I am trying to autofocus on a very distant object ( > 50m for example or near infinity) at short focal lengths, the autofocus will not lock on. I can make it lock on if I zoom in, lock on, and zoom out again, or switch to manual, but both are a pain, when it shoudl be able to focus.

I was wondering if it was a lack of contrast when zoomed right out for a wide landscape shot?
Seems to happen in all lighting conditions too.

I have heard that Tamron zooms can be slow and noisy when focussing (true) but cant figure out why it won't lock on.

Does anyone else get this, or can suggest a fix?

Cheers!

[mick711]

Your Pentax KR have the last Firmware or other ? For information last is 1.14

Can you test your lens on other Pentax device like K5 or other ?

It's possible a Firmware bug of the KR or hardware or a lens problem just you need to know the bad device

[wax]

Hi

I have the above lens on my K-r, and it's a really versitile lens and produces some good images for my level of photography

However if I am trying to autofocus on a very distant object ( > 50m for example or near infinity) at short focal lengths, the autofocus will not lock on. I can make it lock on if I zoom in, lock on, and zoom out again, or switch to manual, but both are a pain, when it shoudl be able to focus.

I was wondering if it was a lack of contrast when zoomed right out for a wide landscape shot?
Seems to happen in all lighting conditions too.

I have heard that Tamron zooms can be slow and noisy when focussing (true) but cant figure out why it won't lock on.

Does anyone else get this, or can suggest a fix?

Cheers!

Is lens matter. my Sigma 18-200mm DC also struggles to focus on low light at long focal lenght. I believe it´s min f6.3 aperture fault. Try to focus on contrasts objects near to your target. or use it on manual.

[mick711]

Is lens matter. my Sigma 18-200mm DC also struggles to focus on low light at long focal lenght. I believe it´s min f6.3 aperture fault. Try to focus on contrasts objects near to your target. or use it on manual.

18 200 lens i agree i have this issu to but now for sport i use 70/200 Sigma 2.8 HSM EX DG

[davea66]

Sorry for not replying to you guys earlier!
In the end I solved this problem by investing in a Pentax 18-135mm zoom. What a difference, best lens I have ever bought and now rarely leaves my camera!

[wax]

Sorry for not replying to you guys earlier!
In the end I solved this problem by investing in a Pentax 18-135mm zoom. What a difference, best lens I have ever bought and now rarely leaves my camera!

Jajaja(lol)
I did the same thing replaicing my Sigma 18-200mm when my K-5II came with a 18-135m as a kit. The Pentax is greatly better lens than the Sigma. No more halo around subjects.

[veedee]

Hi everybody,

I just bought that lens on ebay and I seem to be having exactly the same issues with it like davea66, although it looks brand new:
at18mm the AF would hardly ever focus on anything that is futher away than about 3m. wide angle landscape pictures are next to impossible....
Which means: I have to zoom in, then aquire the focus, kepp half pressed, and then zoom out and take the picture. or go manual.
And the AF is loud, indeed.
I updated my firmware about a month ago so that is not the problem here.

Any ideas? (other than getting rid of the lens and buy a sigma zoom)

[matt_not_andrew]

I had the same issue with mine refusing to autofocus. I sent it back and bought a second hand Pentax 18 250 for less money and have had no problems since. Never found out what the problem was though.