Weird behavior - quick refocus when zooming DA*16-50/2.8 PLM on K-3 III

Hello MarBa

MarBa wrote:

Hi everyone,

I noticed that sometimes when zooming with the DA*16-50 lens, the K-3 III camera would activate AF (red light turns ON for a short moment) and refocus the lens quickly back and forth (very obvious in the OVF!). This happens always at the same focal length when zooming in or out .. but it does not seem to be always the exact same focal length on different occasions (not 100% sure about that). Interestingly, the "MF" symbol also appears in the viewfinder at the same time when AF is activated. I tried to clean contacts on the lens and the camera but it still happens. But often .. a bit later in the day .. it just stops doing that ... so it's weird, not perfectly reproducible.

Anyone noticed something like that? With this combination, or other lenses/cameras?

Best,

M

I have not this lens and also not this camera, therefore I need your help for to answer your question:

1.) You are at 16mm and focus - now you switch off the camera - than you zoom to 50:

Is the 50mm position very unsharp now ?

2.) you switch on the camera - get the 50mm position now suddenly in focus ?

When you think that the camera use a focusing:

start again with step 1.)

and than: cover the lens with the cap, switch than on the camera, wait a little bit, switch off the camera - put off the lens cap: is the 50mm position suddenly sharp ?

My 55-300mm PLM must change the position of the focusing lens group, when I zoom, for that the lens is able again to focus from infinity to the min. distance in this other zoom position. This happens not mechanical by changing the zoom position.....it is done by the PLM itself, who move it's focusing lens group to a new position. But it do this so good, that the lens looks like a parfocal lens. Maybe your lens do the same, and all what you see is that after this generell position change (do to a zoom position change) your camera do a new focusing at specific changes for to stay very precise on the focus you had before you zoomed.

best regards. KPM2