K3 centre focus point issue

I think I “may” have a problem with the centre focus point on my K3 in certain low contrast situations.

In some what might be described as low contrast situations i.e. a leaf or branch within a bush or the shadowed grooves of a door surround my K3 set on centre focus point refuses to lock focus, it goes through the motions a couple of times then just stops without achieving focus However, if I change the focus point to one of the surrounding eight points focus lock is achieved immediately which leads me to believe I have a K3 with a dodgy centre focus point.

This happens with all my AF lenses although it is most notable on the DA*16-50 and DA 100WR Macro, has anybody else has come across the likes before I pack it off to JP Solutions?

I think mine does something like that in low contrast situations. It seems to give up and focus on something close by.

Hi Dave,

I saw your other post regarding focus issues, I'm still not certain I have a problem K3 but it's getting more likely every day.

Today I spent some time with the camera on a tripod and AF fine adjustment with my long lenses, DA55-300, DA*300 and Sigma 150-500 OS and a cornflakes packet.

I'm still evaluating the results but with my eyesight and varifocal glasses I'm not at all certain I can evaluate the images correctly.

One thing I did find out that may help if using the rear AF button to focus, in menu page "AF Button" and with "Enable AF2" selected you can fire the shutter when focus has not been acquired or confirmed, if it is set to AF1 the shutter will not fire until focus has been confirmed.

I don't have this issue with mine, see other post for my thoughts. It works really well with the 150-500 and with all other lenses tried so far.

Regards
David

Hi Dave

Does setting AF2 allow you to release the shutter when the images is not in focus?

It depends on another menu setting, if using 'AF.S', item 15 in the menu allows you to specify if the shutter can be fired whilst the subject is not in focus. I just leave mine on option 2 which is 'Release Priority', i.e. the photographer has control over when the shutter fires, whether the subject is in focus or not. As an aside, I almost always use 'AF.S', I prefer to press the AF button again if I need to re-focus, rather than the camera doing it automatically.

Regards
David

OK, looks like I do have a problem then

In the custom menu items 15, 16 and 17 are all set to Focus Priority.

In the Button Customization menu.......

AF Button" menu set to AF1 the shutter will not release till focus is confirmed with focus priority set for AF.S in the custom menu.

AF Button" menu set to AF2 the shutter can be released without achieving focus even though focus priority is set for AF.S in the custom menu.

Do I have a problem body?

Just magnify the image preview in the camera. that's what I do

After a bit a Google research and playing with my K5ii (forgot I had this on the shelf what I describe above appears to be normal.

That's a good suggestion but you have no idea what it's like trying to compare 2 scenes with varifocals, they are a nightmare for photographers (even worse when one eye is dominant and the other is useless, Amblyopia).

You don't have to compare two scenes when calibrating lenses, or am I missing something?

I find it easier to shoot the same images at different calibrations, then compare them side by side in the Photoshop 'tiled' view at various magnifications. This gives direct comparison between the images on the same computer screen. Once I've narrowed down a range of adjustments, I'll re-shoot a few more at the narrower range and then choose the best compromise at different focal lengths. This doesn't take long to do and has always worked for me.

Regards
David

I just take a pic ( usually at an angle on a sheet of text ), magnify it in camera and see if it FF's or BF's. I may repeat that a few times for consistency's sake.

I'll then change AF parameter accordingly and reshoot a few pics ( checking them each time in cam ). If that's nailed it great, if not I'll adjust some more. it only takes a 2 or 3 adjustments at most to nail it.

If it's a zoom I'll do some at different focal lengths


I'll then spend a few minutes just shooting all kind of stuff just to confirm.

Once I'm satisfied I'll bulk delete all the pics from the card and move on to the next lens


I couldn't be doing with all the hassle of loading them onto the computer then then loading them into some program to tile them side by side. You must be a glutton for punishment.

If eyesight is so bad would it not be better to use an alternative process that removes this constraint?

i.e. autofocus on something like a wall parallel to your camera back using LV/CDAF then switch to optical and AF again. If the lens moves when refocusing then adjust its fine calibration until it doesn't.

Ha!! you pre-empted my next question Rob.

Does dialling in lens AF fine adjustment affect both CDAF (on sensor) and PDAF (viewfinder) auto focus?