Photographers' Formulary Excel Film Enhancer will give your favorite film developer increased shadow detail and film speed ability, while reducing the grain and developing time. It gives crisp, easy to print negatives without blocking the highlights. EXCEL is an easy to use non flammable liquid concentrate, which can be used with diluted or undiluted developers by keeping the ratio of 30 ml per liter. Excel is excellent for low light photo sessions and improves push processed films. Shelf life is 1 year in a tightly sealed bottle.