One of the most important questions people ask is, how large of a picture light do I need? It's important to remember that there are general guidelines but no hard and fast rules. The general guideline for traditional picture lights that have a two inch diameter shade, such as these House of Troy antique brass picture lights, is that the light should be at least half the width of the image you are trying to illuminate. Meaning that if you have a 20 inch wide image, you need at least a 10 inch wide picture light.
