Sharp vs. Focused, and Depth of Field
Written by: Tiffany Joyce
A photo has to be in focus in order to be sharp, but a photo does not have to be sharp in order to be in focus.
This photo is sharp (click to see original size):
Zoomed in to original size, you can see that every detail of the motorcycle and motorcyclist are very clear, with defined lines and crisp edges.
Now, this photo, while not sharp, is still in focus (click to see original size):
This technique is called “soft focus”. Zoomed in to original size, you can see a slight smudging of the details, and the lines and edges are not as defined. Yet, when viewed in its entirety you can see that while soft, the focus is clear.
A photo can have aspects that are both tack sharp AND in soft focus, or out of focus completely. This is especially true of macro photography and when using very large apertures. You see, basically speaking, sharpness is related to how much motion is introduced to the photo while in the process of being taken – or “camera shake”. A perfectly still camera will result in a “tack sharp” photograph.
Focus has to do with the image plane and circles of confusion… which has a long and drawn out explanation so, to put it simply, focus is directly related to your depth of field. “Depth of Field” refers to how much of the photograph is in focus. You may think, but wait, isn’t the whole thing supposed to be in focus? Sometimes the answer is “yes,” but sometimes it is better to have only specific parts of the photograph in focus. The amount of focus in a photograph helps to draw the viewer’s eye toward the key component of the scene. It can be a powerful tool for creating atmosphere and mood, for communicating a message, and for compelling emotion from the viewer.
This photograph has a wide depth of field (in this case f/16) – notice all aspects are “tack sharp”:
This photograph has a shallow depth of field (f/2.8) – notice the buds of the cactus are in sharp focus, but the remainder of the photo has increasing levels of softness until it falls out of focus entirely:
As you prepare to take a photograph, it helps to envision the subject or scene in front of you as a series of vertical layers or planes – the literal depth of the field of vision in front of you. The point immediately in front of you is one layer, a point a few feet beyond that is another layer, a point beyond that is another layer, and so on. A shallow depth of field may reveal the first one or two layers in focus. A large depth of field may reveal all of the layers in focus, out to the horizon.
As you can see, sharpness, focus, and depth of field are all related, but are not all the same thing. The terms are often used interchangeably, so I hope this has helped to clear up some confusion! Here are some additional articles that you might find to be helpful:
Photo credits (in order of appearance):
- “The Doctor” by Tiffany Joyce.
- “Rose” by Stephen A. Wolfe on Flickr Creative Commons.
- “Portland Head Light” by Tiffany Joyce.
- “Cactus Bud” by Tiffany Joyce.
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