A photo of a whiteboard or a printed page is often just legible enough to be frustrating. Adjusting the tones usually fixes it.
Text is readable when it separates clearly from its background. Most unreadable photos of text are not out of focus, they are low contrast, so the letters and the paper sit at similar brightness. Widening that gap does more than any sharpening.
Removing colour helps more than people expect. Whiteboards photographed under fluorescent light go slightly green or blue, and dropping to black and white removes that distraction entirely, leaving only light and dark.
Genuine blur cannot be fixed. If the camera moved or missed focus, the detail was never recorded and no adjustment recovers it. Retake it if you still can.
Take Black and white to 100 percent and raise contrast to somewhere between 130 and 160 percent. That separates dark letters from the light page. Add a small amount of brightness if the whole picture is dim, and leave saturation alone, because colour adds nothing to text.
If the next step is reading the words with Image to text, a high contrast black and white copy usually gives better results than the original photo. Save it as PNG so the edges of the letters are not smudged.
No. If the detail was not captured it cannot be restored. Low contrast can be fixed, blur cannot.
Often yes, especially for whiteboards and printed pages under artificial light.
No.
Between 130 and 160 percent works for most photos of printed pages. Too high and thin letters begin to break up, so check the preview.