LX100 Focus Issues

LX100, 1 Area AF, center, AF box size 4/15

A few days ago  I made a sequence of photos of a group of people moving across in front of the camera. (not the photo above) I decided to use Manual Focus and set up prior to the sequence of shots. I focussed on a part of the scene which was about the distance from the camera which I estimated would give me sufficient depth of focus at the aperture in use.

Had I allowed AF to operate the camera would have focussed on the closest person which was not what I wanted.

So I set the LX100 to manual focus and used peaking to find the in focus point.

I made the series of exposures and on review found them all out of focus even at the distance which I thought was in focus.

Back at home I did some experiments comparing accuracy of AF with MF. For manual focus I tried 

Peaking on and off, high and low.

With a range of different subjects at different light levels I found the AF frames were usually sharper than the MF frames.

Why ? 

In the process of focussing manually several hundred times I discovered that the peaking effect is not peaky enough for consistently accurate focus. I had to turn the focus ring a substantial distance to pass from one side of the peaking display to the other.  The on screen analogue style virtual distance display moved a considerable distance during the to and fro process as I was trying to find the peak of the peaking. 

I had no better luck with peaking switched off. 

I found no significant difference in accuracy between the high and low peaking settings.

Conclusion  In my hands AF is more consistently accurate with most subjects than MF.  It is also much faster.

A better Way:   AF + AF Lock

For those times when I want to set and lock focus for a sequence of exposures I use the following:

1. In the Custom Menu Page 1/9 set the AF/AE-Lock button to AF Lock.

2. Next tab down set AF/AE Lock Hold to ON.

3. To focus place the AF box over that part of the subject required to be in focus and press the AF/AE-L button.

4. The AF box changes from white to green and a little green dot appears top right on the image preview indicating focus is achieved.

5. Many frames can now be shot each at the same focussed distance.

Notes:

*  Focus is cancelled if the zoom lever is moved.

*  If [AF+MF]  is ON (Custom Menu Page 3/9) then manual focus is activated by turning the lens ring. This cancels focus lock. I find it too easy to bump the lens ring which turns at the slightest touch,  so I have [AF+MF] OFF. 

I find this method is usually faster and more accurate than trying to focus manually.

However……………

Sometimes autofocus gets it wrong

I have found that Panasonic cameras, including the LX100 which use contrast detect autofocus have an excellent record of AF speed and accuracy. But there are still some subject types which can give problems with any of these cameras.

* Obviously a featureless flat surface provides no contrast on which to focus.

* The AF system is not responsive to a subject with horizontal lines (in landscape orientation) if there are no vertical lines or texture.

* Multiple small lights like those used in Xmas decorations are often rendered out of focus.

* Other types of lights in the AF box can unsettle the AF system although less frequently than the small spherical decorative ones.

I suspect the problem here is that local flare around an in focus light source is difficult to distinguish from a slightly out of focus rendition of the same subject element.

* Dense, fine foliage seems to present a problem for the AF system in my experience.

I find I can usually manage subjects such as those described above by:

* Being aware of potential problem subject types.

* Selecting a more AF friendly part of the subject (with clearly defined shapes or vertical lines) and using the AF Lock/Hold strategy described above.