Rediscover - Understanding Sharpness

By Michael Reichmann - Originally Published March 11, 2011
 What Are We Talking About?
Photographers as a group are pretty hung-up on sharpness. I'm no exception. Unfortunately for some seeking the holy grail of ultimate image sharpness becomes a substitute for creating interesting and worthwhile photographs. Since the concept of sharpness is a means, not an end in itself, I thought it worthwhile to look at what is meant by the word sharpness as used in photography.
It actually consists of two separate concepts —  resolution and acutance.
With this article, I hope to explain these two concepts and the role each plays in our perception of what is sharp.
Photographed with Canon D30 at ISO 400. 1/250th sec @ f/5.6 with a Canon 300mm f/2.8L IS .  RAW Mode.
What You Get May Not Be What You See
The traditional measure of image sharpness is stated in line pairs per millimeter — abbreviated as lp/mm. In other words the ability of the human eye to discern the number of high-contrast pairs of l...