Few things are more disappointing than reviewing a promising shot on your computer only to find the focus landed on the wrong thing or the whole image is softly blurred. Sharpness problems are among the most common frustrations in photography, and they rarely come from a single cause. Understanding the handful of factors that determine whether an image is crisp lets you diagnose your own misses and fix them systematically rather than guessing. Separate the Two Kinds of Blur The first diagnostic step is distinguishing focus blur from motion blur, because they have completely different solutions. Focus blur means the focal plane landed in the wrong place; one area is…