Manual focus has been my biggest challenge so far. Today I decided to wear a pair of readers and then adjusted the diopter accordingly. I generally wear progressive glasses and do not wear them when I'm shooting photos. This is proving to be an adjustment.
When you shoot at f4.0 or f5.6 you get a larger sweet spot then if you are shooting at a smaller aperture, such as f2.5 or f2.8. Since it is recommended, as a beginner, you start with f4.0 or f5.6 looking through the viewfinder is a bit darker than shooting wide open, but the area of focus is larger. It is still a bit difficult to see clearly with my old eyes and strong readers. At the end of the day, I found it a bit easier to see the sweet spot of focus with the readers and I think I'm making some progress.
Tonight I started in the photo cube where I could control the light. I also used a tripod since I'm finding that the smallest amount of camera shake is obvious. Here are a few images. You can see the area of focus, although it wasn't exactly where I thought it was going to be. Still need work and practice.
The next two 'practice shots' were taken in the early evening sunshine. Just by looking I think these were probably at f2.8 or f2.5. I was happy with the texture and blur of the background behind the raspberries and the sharp areas of focus in the iris photo.