Photography Lesson 2
Pinhole Camera
Lenses
The Pinhole Camera
• as light strikes an object, it is reflected, scattered
in all directions
• here we see the light that is scattered from a
single point on this apple. the light travels in
virtually every direction simultaneously, and
strikes a flat surface multiple times
• here we see the light that is scattered from a
single point on this apple. the light travels in
virtually every direction simultaneously, and
strikes a flat surface multiple times
• Imagine that there is a wall with a tiny opening in it
between the apple and a reflective surface. Only the light
that is traveling in a straight line from one particular point
on the apple will pass through the opening.
• if we follow the path of light from any other point
on this apple, the same result occurs
• if we follow the path of light from any other point
on this apple, the same result occurs
• if we follow the path of light from any other point
on this apple, the same result occurs
• every point on the apple will reflect light that will
travel in a straight line through the aperture. The
light from each of these points forms an inverted
image on any surface opposite the aperture.
• every point on the apple will reflect light that will
travel in a straight line through the aperture. The
light from each of these points forms an inverted
image on any surface opposite the aperture.
• when the back wall is enclosed in a darkened
chamber, this simple design is known as a
pinhole camera. Typically, light sensitive film
would be placed against the back wall.
• when the back wall is enclosed in a darkened
chamber, this simple design is known as a
pinhole camera. Typically, light sensitive film
would be placed against the back wall.
• Pinhole cameras require very small apertures
that are typically made with a pin-prick. As light
passes through the small aperture, it produces a
small, accurate circle of colored light.
• Pinhole cameras characteristically let very little
light in through their small openings, and
therefore must compensate with relatively longer
exposures.
• A larger opening on a pinhole camera would not
produce satisfactory results. The light that
enters a larger opening spreads out before it hits
the surface of the film.
• Soft, overlapping circles result, producing an out
of focus image. While the exposure time will
certainly be lessened, this comes at the expense
of focus.
• a Lens solves both of these issues, allowing
sharper focus and shorter exposure time.
The Lens
From Pinhole to Lens
• A pinhole, as small as it is actually admits
a cluster of light rays. Coming at slightly
different angles, these rays continue
through the hole in slightly different
directions.
• A Lens creates a sharp image with
relatively short exposure. To get sharp
pictures, the image of a tiny point should
also be a tiny point
• The most important way lenses differ is
in their focal length.
• Technically, focal length is the distance
between the lens’s rear nodal point and
the focal plane when the lens is
focused at infinity.
• Focal length controls magnification, the
size of the image formed by the lens.
The longer the lens, the greater the
size of objects in the image.
• Focal length also controls the angle of
view, the amount of the scene shown
on a given size of film
• Normal-focal-length lens, also
called a standard-focal-length
lens, approximates the
impression human vision
gives. - faster
• Long-focal-length lens
provides greater image
magnification and a narrower
angle of view than a normal
lens. Long lenses are excellent
when you can not or do not
want to get close to the
subject. – slower
• A short-focal-length lens
increases the angle of view
and shows more of a scene
than a normal lens used from
the same position. – wide
angle lens
Zoom Lens
•
•
•
•
•
Zoom lenses are popular because
they combine a range of focal
lengths into one lens.
Using a 28 – 105mm zoom is like
having a 28mm, 50mm, 85mm,
and 105mm lens instantly
available, plus any focal length in
between.
Zoom lenses tend to be a little bit
heavier, more expensive, and
bulkier.
Zoom lenses are best used where
light is ample because they have a
relatively small maximum
aperture.
Zooms that keep the same
aperture at all focal lengths are
complex designs and therefore
relatively expensive.
Macro
• A macro lens is useful for extremely close
shots
Fisheye
• For the widest of wide-angle views,
consider the fisheye lens.
Focus and Depth of Field
• As we’ve discussed, You can use the
aperture to control the depth of field.
• There are two other ways to control or
adjust your depth of field.
– Focal length
– Distance from the subject.
Again, the smaller the aperture, the greater the
depth of field.
same focal length, staying at the same distance
• The shorter the focal length of the lens, the
greater the depth of field.
• Same aperture, set at same distance
• The greater the distance from the subject, the
greater the depth of field.
• The pic on the left was taken at 3ft, the pic on
the right, from the same lens and focal length
with same aperture from 10ft farther away.
• Why does a lens of longer focal length produce less depth of field
than a shorter lens used at the same f-stop?
Equivalent Exposure
• f/2.8 @ 1/500 =
f/5.6 @ 1/125
f/22 @ 1/15 =‘s
f/16 @ ?
? @ 1/250