K20D and 50mm FA 1.4 problem

Merry Christmas Everyone,

Have a little problem and wonder if anyone knows a solution. My Pentax FA 50mm 1.4 lens seems to have a problem focusing to infinity. It can focus on anything else and seems sharp but when I go beyond it's 10mm mark it just doesn't want to lock. K20D just has a flashing green light saying can't lock on.

I tried other lenses and they work fine. This problem also exists if I try to manually focus. Lens's range indicator says i'm at infinity but camera doesn't lock.

Anyone had this problem or know a reason for it?

Lens worked fine but I'm guessing a bump inside a bag might have caused some misalignment to take place. I got the lens from SRS a few years ago so it's not under warranty anymore.

Cheers for any help

Dan

What are you aiming the lens at, and has the problem ocurred on more than one day or with more than one subject?

The subject needs to contain a certain amount of contrast. An overcast sky or misty scene may not be good enough, for example. Try focusing on different parts of the subject until the camera does lock on.

This lens may be more difficult to focus than your others due to its shallow depth of field while it is wide open.

ps. You don't need it to lock on in MF mode. Then you can just ignore the focus indicator and shoot.

Hi Pete,

I have tried different subjects and various distances. It's not locking on. And in manual focus camera offers a assist by letting you know you focused but it doesn't do it in this case.

Dan

As a first step I would clean the contacts on lens and camera with a soft cloth. Then remount the lens and try again.

Check that the lens focusing rotates fully whilst the lens is off the camera and also check manual focusing when on the camera. In the latter case ignore the green hexagon and trust in your eyes to see what is happening. Then finally switch to AF and try that again.

Hi John,

I have given that a go, cleaned the contacts, then tried the lens on again. Lens rotates fine off and on the camera but when it gets to a certain point (more than 10 meters) it just fails to be in focus. I double check the viewfinder adjustment slider too to make sure that was all okay and used lens in manual focus mode just trying to get a sharp picture inside the viewfinder but it's not happening. My other prime lens Tamron 90mm seems to be fine.

I also check that the rubber focusing ring is correctly in place and doesn't get in a way.

Dan

It's very difficult to see what else may be amiss without having the lens and camera to hand. Do you know someone else with a Pentax SLR who could try the lens on their camera?

I had the same problem with a Tamron and that was due to a bump.
Not saying yours is but its certainly a possibility.

Hey,

I got a friend who has a K-m I can try the lens on, will see him tomorrow. I'm rather confused by the problem myself. It focuses fine close up but not on far off subjects. I dropped that lens months ago from about knee height onto a carpet and it was fine until today.

Mike, how did you fix your Tamron lens?

Cheers all for replies

Dan

Mine was dropped from about the same height onto a hard tiled floor. Was the same, could focus close up but no chance on subjects further away .. also I could manual focus but no confirmation and it was all blurry
Sent it to the main UK Tamron repairer/importer (Intro2002) who had it for 7 months before deciding they couldn't fix it and so sent me one in Canon mount(as it's no longer made, they had destroyed mine trying to fix it and they are as rare as rocking horse droppings in Pentax mount).

Interesting, I don't trust repair services either. My friend sent in his sigma 17-70 f2.8-4.5 for repair once and it never did 2.8 at 17mm again after that.

I just had a look and a photo i taken couple of weeks ago (12/12/09) of a bridge, and that looks sharp. 50mm wasn't used much this past two weeks but I did screw on a skylight filter on it when it was snowing a few days back to grab some pics (never did that) so it was just sitting in my bag. Maybe something pressed on it or it was bumped against something hard.

Puzzle. Might take it to SRS and see what they say. I can still shoot portraits with it though.

If it still misbehaves on another body it might be worth getting Asahi Photo to have a look at it. They did a good job of sorting out a Pentax zoom of mine which had taken a knock a few years back, for reasonable money.

http://www.asahiphoto.co.uk/

Kevin

Hey Kevin,

Cheers for that info, I'll give them a call next week.

Dan

Just an update. I tried my friends K-m with the FA50 and it started to focus fine again. Put it back on my K20D and it's all good again. Can't say this is something I can explain. The only thing that springs to mind is lens was reset on K-m to original focusing alignment somehow.

It was a Christmas miracle I guess

Thanks for all the help guys.

All's well that ends well!