On certain Sony DSLRs and mirrorless cameras, you can set the auto-focus feature to lock on a subject in the middle of the screen. To use Center Lock-on AF, select Menu > Focus Mode > Continuous AF (AF-C) > Focus Area > Lock-on AF: Center. Then, compose your photo so that the subject is in the on-screen frame, press the shutter halfway, and push the shutter button completely to take the picture.