20mm 1.8 autofocus jumping

[Amadeus2020]

Hi. I have a brand new SONY 20mm f1.8 lens. SEL20F18G, attached to an A7iii.  When in continuous focus, the image on screen jumps in and out considerably as the autofocus is moving around. Is this normal? It 'zooms' in and out quite a lot as the internal mechanism moves forwards and backwards trying to find the focus. I have never seen it before on a SONY lens (I have the 55mm prime). It does not occur when the camera is in Auto, but is quite pronounced when it is in AP mode. 

[Peter_S.]

Hi Amadeus,

Try to use a different aperture other than 1.8.

Guess there's too much light getting onto the focus sensor.

Cheers

Peter

[Amadeus2020]

Hi. Thank you for replying. Actually, it is far worse at f8, 9, 10 and higher. When it's at 1.8 it's pretty stable.

[Joe_Dohn]

Does this happen on the latest software version as well? I recall seeing some restrictions on this lens with the camera which recommended the latest software version (if I'm not mistaken).

[Amadeus2020]

Thank you. Software? Do you mean the firmware for the A7iii? I have googled it and found nothing. Sony has no updates that I can see pertaining to the 20mm.

[Win_88]

Hi @Amadeus2020

I found a firmware update on the Sony website for the A7III:

https://www.sony.co.uk/electronics/support/e-mount-body-ilce-7-series/ilce-7m3

Win_88

[Amadeus2020]

Thank you that's helpful. I've updated. But Sony tell me that's completely normal for this lens because of the internal mechanism (!).

[Win_88]

Hi @Amadeus2020

Having had experience with Sony support myself, If you were given that answer, it must've been the result of an investigation and the info is accurate. It must be within specifications.

Win_88