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Film - Digital

How does focal length of a lens affect depth of field?

When a smaller focal length lens like a 28 mm on a 35mm camera is used there is more areas of the images in apparent focus due to the increased depth of field. Correspondingly with a longer focal length lens such as a 135mm on a 35mm camera the depth of field is very much reduced. when using longer lenses the focus become critical. Also the lens may need to be used on a tripod due to camera shake .

Again note that there is less depth of field closer to the camera position from the point of focus than in the distance. Remember to allow for this by focusing on a point closer than mid way, about 1/3  to 2/3 is the general rule.


Two other factors play a part in depth of field:
subject distance



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