John G Evans c 2019
my honest attempt to comprehend the photographic focal planes within the camera
lens I consulted a brilliant photography colleague of mine whose name I shall
not reveal at this time having no consent to mention her name. However, she
brought to light the mystery hidden within the complex world of photographic
focal planes. Essentially speaking the higher the f/ number the more focal
planes we come to know as being in focus. So, I encountered a PDF online
entitled Basic Principles of Photography by David Capel.
Capel explains illustratively that the Latin ‘Camera Obscura’ = “Dark Room” he explains
also that “light passing through a small hole produces an inverted image on the
opposite wall. Leonardo DaVinci and other artists during the 15th
century made use of this creative technique to sharpen their artistic imaginings.
refinements were designed were utilized by 18th century artists as Canaletto.
The first original photograph was created by Joseph Niepce in 1825 upon light
sensitive silver chloride plates. Thus, I suspect the originating feature
whereas silver film became a useful tool for creating the image upon. I learned
this factor working for a micrographics firm creating silver film and diazo
film images we now call microfiche. I did this for 6 years working in a micrographics
production facility. Looking back, I can now visualize what I was creating,
how, and why.
goes on to further demonstrate that the first production camera (Daguerreotype),
designed by Louis Daguerre (1840’s) became the prototype we all benefit from in
our world today. So, if we fast-forward 150 – years we discover that early
photographers used silver halides on a mirrored – polished hard surface we call
film. But as David goes on to explain present day fundamentals of photographic
reception, we learn digital cameras employ electronic sensors consisting of
large number of square cells or pixels.
smaller aperture or opening means we receive little light or subject matter
visibility. A larger aperture or opening means we receive more light rays or
subject matter visibility. With the lens we add to the camera we receive rays
of light on a singular point creating a sharper image.
also demonstrates as I have aspired to explain as correctly as I am able as a somewhat
novice/want-a-be-portrait-photographer a formula (that which I have discovered
useful), that shows us 1/D’ + 1/D = 1/f. This formula translates to points at
distance D are focused on D’ plane results in the subsequent turning of the focus
ring to move the focal plane rendering us a more focused image (whether on film
or a censor or even in a pinhole camera a wall). So, the field of view depends
upon the focal length f that is a distance from the aperture to the censor (or
doubling the focal length, we receive half the view. Essentially, a short focal
length we see a wide field of view, but, a long focal length we see a narrow
field of view. For a known or given film size s and focal length f plus the
angular field of view the formula would look as such:
= 2 arctan s/2f
a Perspective Convergence your short focal length (wide FoV), images tend to
exhibit pronounced perspective effects. A wide FoV near to subject parallel lines
converge, and with a narrow FoV far from subject parallel lines remain
parallel. By increasing focal length and moving further from subject we can
drastically change the composition.
problems I encountered over a specific composition I was working with first at
f/1.2 then f/5.6 and still being out of focus as I was told by a colleague was
motion blur as opposed to focal planes, but in the process of discovering why
my focus was not sharp, I thought more light was necessary on the subject to be
able to focus clearly on her closest eye. Once in focus everything within that
particular focal plane should be in focus. f/1.2 gave me a wider aperture
opening to receive more light rays and subsequent image transferred TTL (through
the lens), and when I modified the focal plane to f/5.6 I remained out of focus
with the exception of the model’s face. So, my friend instructed me to photograph
at f/4.0, 1/160 s, ISO 100, with a lamp power decrease to 1/64s. This
was a super starting point.
a determination to manipulate the camera and lens to work to my advantage I
begin at this point. Adjustments are made until I am completely satisfied with
the end result.
this point I wish to thank David Capel for his photographic evaluation of focal
planes and focal lengths through his valuable article in a PDF format. Without
his research I never would have understood more clearly. All credit is and
should be rendered to David Capel for assisting me to write out the measures he
has taken to research, write, and illustrate this 44 – page PDF article I used
to try and understand more about focal planes and focal length. Thank you,