Focus Lock Problem with ist DS

Dear All

I have a *istDS with the latest firmware.
I have it set to use AF-S, i.e. single shot AF mode.
I use the apertue priority mode.

My problem is that I expect the camera to lock the focus when pressing the shutter button half way *and* the focus lock indicator is lit. This works most of the time but sometimes when I go to press the shutter fully, the camera shifts focus again before taking the shot. E.g. if I depress halfway, lock focus, move camera slightly keeping button halfway depressed - it can make the camera hunt again for focus. Is this normal?

If I change the settings such that the OK button does the focussing, this seems to work. In fact this is a useful feature as I can focus with OK button, release it and then press the shutter button to take the shot.

Anyway, I was wondering if I have a faulty camera regarding the above problem? I seem to remember seeing some reference to this a while ago when trawling the net for answers.

If there is a fault, does anyone have any idea how much it would cost to fix? I ask this because I am thinking of upgrading from to K20D and would like to 'donate' the DS to my partner but only if it works properly the normal way!

Thanks

Lee

Doesn't sound right to me.

Most likely, I think, is that either your finger is coming off the button momentarily before fully pressing, or the button is faulty.

First I would double check it really is on AF-S mode (check the menu setting), and Av. (Sport mode puts it on AF-C).

Thanks Pete. I think I have checked every combo possible. I'll have another look.

Lee

Before I send the body off for a repair quote can anyone think of a legitamate circumstance where this would happen?

i.e. I press shutter button half way, get focus lock confirmation in viewfinder and audible beep and then when pressing shutter button fully, camera refocuses before taking the shot?

Lee

I found that it happened very occasionally and focusing on something else instead always cured it. Maybe under some circumstances the AF system is confused and doesn't lock properly.

AF systems dont like horizontal lines eg venetian blinds