Why are f/8 to f/11 commonly recommended for landscape photography?
Asked 6/14/2020
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If a distant subject like mountains is already within the depth of field at a wider aperture, why do landscape photographers often still choose around f/8 to f/11? For example, with a 70mm lens on full frame, hyperfocal distance at f/2.8 may already put distant scenery in acceptable focus. What practical advantage does stopping down to f/8 or f/11 provide?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
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Depth of field refers to the distance between the nearest and farthest objects that appear "acceptably in focus"; it does not convey information about absolute sharpness in the resulting image. All lenses suffer aberrations of various kinds, and these aberrations tend to be the strongest at the perimeter of the lens, where they are harder to correct for. Stopping a lens down reduces the contribution to the image from these peripheral parts of the lens and thus tends to increase sharpness in the plane of focus. At very small apertures diffraction comes into play and reduces sharpness again.
For a typical small-format lens, the sweet spot that minimizes information loss occurring from both aberration and diffraction is likely to lie close to f/8, hence the "universally agreed" rule of thumb you mention. To illustrate, here is a series of 100% crops of a book cover photographed from a distance of about 0.3 meters using a 50mm lens on an APS-C sensor (the detail is about 1cm x 1cm):
f/3.5 – largest aperture of this lens. The subject is in focus but not necessarily very sharp.
f/8 – this is better
f/22 – smallest aperture of this lens. Again, the subject is in focus but now appears blurry because of diffraction.
Originally by user83032. Source · Licensed CC BY-SA 4.0
user83032
6y ago
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Because depth of field and maximum sharpness are not the same thing. A wide aperture like f/2.8 may already place distant mountains within acceptable focus, but many lenses are not at their sharpest wide open. Lens aberrations are usually stronger toward the outer parts of the glass, and stopping down reduces those aberrations, often improving image sharpness at the focus plane.
For many lenses, the best balance between aberrations (worse wide open) and diffraction (worse at very small apertures) is often around f/8, which is why it became a common landscape rule of thumb.
Another major reason is composition: landscapes often include foreground elements as well as distant scenery. Using f/8 to f/11 increases depth of field so nearby objects are more likely to look acceptably sharp too.
That said, it is not a universal rule. If your scene has no important foreground, or you prefer a different look, a wider aperture can be perfectly valid. Choose the aperture based on your priorities: overall sharpness, foreground-to-background focus, shutter speed, or creative effect.
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