I have just finished posting for sale the ebook versions of Photographer’s Guide to the Sony DSC-RX10 II, a follow-up to my earlier book on the RX10. The new book has 318 pages in the printed version, and more than 450 color photographs or illustrations. The book covers all features, menus, controls, and functions of the RX10 II camera. For more information, please see the book’s main page at this site.
I just learned that Sony has released a firmware upgrade to Version 1.20 for both the RX100 IV and RX10 II camera models, which are quite similar in their menu options and operation. The upgrade provides the same change for both cameras. According to Sony, the purpose of the new firmware version is to “improve a focus shift condition with HFR (High Frame Rate) recording.” That problem evidently is the one discussed in this thread at the dpreview.com forums.
That is all the upgrade is designed to do, so, if you don’t use HFR recording (super-slow-motion video recording), you may not need the new firmware. However, I always install new firmware versions as they become available, and it probably is a good idea to install this one as well.
To get the new version for the RX100 IV, you can go to this link at Sony’s support site. You then have to select your computer’s operating system to get to the page with the file to download and the instructions for installing the update. Here is a link to the similar page for the RX10 II.