Effect of Aperture on
Single Frame Depth-of-Field and
Rik Littlefield (email
rj.littlefield at computer.org)
Shallow depth of field is a
problem when photographing small
things. Stopping down the lens is not a complete solution.
some optimum point, stopping down the lens reduces geometric blur but
makes the entire image fuzzy due to diffraction effects. When
photographing something the size of a housefly, the optimum point is
typically f/8 or wider, and the useful depth of field ("depth of
detail") for a single picture is often 0.1 mm or less. The
problem becomes more severe with smaller subjects.
Page written May 11, 2005,
Revised August 19, 2005,
Last minor edit April 25, 2009.
below are typical results, obtained with a Sigma 105 mm f/2.8
macro lens at 1:1, on a Canon Digital Rebel camera (22.7 x 15.1 mm
sensor size). The subject
is a Small Pearl-bordered Fritillary (Boloria
selene), tipped at roughly 45
degrees to the optical axis. A single full frame is shown at
right; crops showing more detail appear in the series below.
If the goal is maximum detail, then
the optimum aperture for this lens under these conditions is only
around f/8-f/11 (see series below). Stopping down farther results
in progressively less
detail. Resolution is obviously degraded even at f/16 and becomes
worse with smaller apertures. At f/45 the image would be noticeably
fuzzy even in a 4x6
Unfortunately, at f/8 the depth of high resolution in a single frame is
0.015 inch (0.375 mm).
Extended-depth-of-field software, such as Zerene Stacker, Helicon Focus and CombineZP,
allows high resolution to be achieved
over great depths. The images labeled "f/8 + EDOF" result from
compositing 35 frames spaced at 0.015 inches, resulting in a total
depth of field of 0.525 inch (13.1 mm).
References and Credits
To the best of my knowledge, the earliest solid technical discussion
of this topic is a June 1960 article by H. Lou Gibson,
"Magnification and Depth of Detail in Photomacrography" (J. Phot. Scty. Amer., 26, 34-46).
It includes a detailed mathematical analysis. An
extended and much more approachable discussion can be found in the
Technical Publication N-12B, "Photomacrography", copyright 1969, now
out of print but still commonly available through used book
In Kodak's N-12B, Figure II-82 provides "A photographic demonstration
of detail ... [using] a butterfly wing tilted away from the camera at
45 degrees". That figure served as the model
for the illustrations appearing in this web page.
The work presented here is a personal publication of capabilities and
techniques developed by the author. You may link to this page,
but please do not reference in archival publications; contact the
author instead. All images and text
are copyright Rik Littlefield, 2005-2009.