Sony DSC-HX90V Manual page 26

[5] How to Use Before Use
Adjusting the viewfinder (diopter-adjustment)
Adjust the diopter scale to your eyesight until the display appears clearly in the viewfinder.
1. Slide the Viewfinder pop-up switch (A) down to raise the viewfinder.
If you slide the Viewfinder pop-up switch when the camera is off, the camera will turn
on.
If you stow the viewfinder inside the camera, the camera will turn off.
2. Grasp both sides of the eyepiece (B) and pull it towards the monitor side until it clicks.
3. Slide the diopter-adjustment lever.
Adjusting the viewfinder