 | |
Night Photography, Canon EOS 5D, 17-28mm, Canon Lens @ 20mm, ASA 1200, f/22, 30 second exposure, Copyright Allison M. Fleetwood Jr. 2007 www.amfjphotography.com |
Welcome to my Blog everyone! You will find herein many tutorials, personal and professional experiences, and a wide range of the images I've created over the previous 20 years. If you have any questions, please feel free to email me at allison@amfjphotography.com, and I will be happy to respond as my schedule allows. I hope you'll visit often, and will find the insights I provide both enlightening and entertaining. I've found through the years that many people who love art, enjoy creating photographs, and yet find the technical aspects of photography a daunting task to be avoided. Reading through technical manuals, and LCD menus on the cameras themselves, often leaves people feeling confused and overwhelmed by the unique language inherent to the science of photography. Anything called an f-stop should be a place to buy gas and grab a bite to eat; while shutter speed and ASA sound like terms Ferrari mechanics would find sexy, but leave everyone else scratching their heads. Demystifying the technical linguistics of photography, and approaching the science in a common vernacular, places the magic of imaging in everyone's hands. Achieving this end, and sharing its applications from the personal and professional side of the house, is this blog's raison d'etre. If you're a lover of dry, purely technical manuals, my blog probably isn't for you. But I certainly invite you to stick around and try something new. If your mind is severely weighted to left brain, logical, linear functioning, at the expense of the right brain's abstractions, who knows, perhaps you'll find my blog of some assistance. A fresh, artistic approach to a hard science might be just what the doctor ordered. And you can always return to those stale manuals if the colorful language makes you woozy. ;-)
My first tutorial begins later today. But first, a bagel with cream cheese and chives, and three, piping hot cups of hazelnut coffee must be consumed. No, not by you, silly, by me. Go get your own writing ritual. This one's mine. ;-)
-- Insert cute, squiggly little line here representing a short intermission (Blogger doesn't have one, so use your imagination. We're talking art here, and you can consider it practice for coming events ;-) --
Okay, freshly bageled and coffeed, I'm ready to begin...
- A Slightly Humorous Aside -
If you feel like raising your hand, sorry, but you'll have to squelch that for the moment, and email me your question. While this is a class of sorts, if you'll notice, you're looking into a computer monitor. You're not sitting in a brick and mortar classroom. If that point escaped you, perhaps a class in abnormal psychology will better serve your current interests. Come back later when you're ready, and I'll be here teaching. These tutorials are meant to be fun and helpful to everyone interested in mastering photography. However, they might also inspire a serious interest in pursuing the business of art. If this proves to be the case, I would be remiss in failing to mention that careers in art, though often misperceived as being cakewalks, are in fact, not for the faint-hearted. Yes, some artist's career trajectories are Apollo spacecrafts right off the launch pad. But most rise in the same manner as do those in any other business endeavor, by means of talent, brains, and soul-wrenchingly disciplined work. Cakewalks aren't applicable. But who wants to walk through cake anyhow? Cake's tasty stuff to eat. But all that sugar would make your feet stick to the floor and slow you down. And in today's fast-paced, ever changing world of the technically driven arts, success in no small way depends upon one's ability to quickly and accurately adjust to new methodologies. Speed inhibiting factors and fanciful expectations don't help. That said, on to the first series of lessons...
Learning To See Through the Camera's Eyes; F/Stops, ASA/ISO, & Shutter Speed
The following is a tutorial I recently wrote to a friend of mine, who is a Commander serving on active duty in the United States Navy. I believe it provides a sound beginning, and presents the fundamental essentials in an easily digestible manner. Enjoy.
Letter sent, December 28, 2011
Hi Charles,
I hope you and your family are doing well, and are enjoying
the Holidays, sir!
On photography for beginners, I will start with the basics,
and if you have questions, let me know and I will get back with you promptly.
Once you feel you've grasped these lessons, I'll move on to the next, more
complicated set.
First, to learn photography well, in my opinion, it’s best
to buy an inexpensive, five feet high tripod with an extender neck, that will
allow the tripod’s head to rise at least another foot. Then shoot with the
camera affixed to it at all times. I'll explain why later, but for the moment,
just trust me in this. Second, always shoot with the camera on Manual. Using
the camera's preset settings (P, AV, SV, TV, etc.) will confuse you until you
understand the basic rules of how cameras record our environment. And third,
turn the camera's flash unit off. Once you understand how the camera sees, then
we'll move on to enhancing photographs with light produced by flash units (also
called strobes), and light produced by what we call “hot lights”. Hot lights,
unlike strobe lights, are most often tungsten balanced light sources that
produce constant light, whose bulbs become quite hot, thus the name. That said,
here are the first three, primary basics of photography, f/stops, ASA/ISO, and
shutter speed.
1) F/Stops are measurements of the opening (or aperture) of
the iris in each lens. The iris is an interior component of all camera lenses,
and plays two, crucial roles in A) achieving correct exposure, and B) altering
what’s called “depth of field”. The iris is formed by overlapping, retractable,
metal leaves within the lens barrel. The rule to remember relevant to f/stops,
is that the smaller the f/stop number, the wider the opening, and therefore the
greater amount of light the lens will admit onto the CCD (charged coupling
device). The CCD is the rectangular, electronic plane within the body of all
digital cameras that receives the light and translates it into an image - it’s
the component that replaced film. The rule on CCD’s is Do Not Touch. Oils from
finger tips make it behave very nastily. Happy CCD = Happy day shooting Aunt
Bessie. Unhappy CCD = Aunt Bessie will want to shoot you. But not with a
camera. ;-)
2) Understanding the relationship between f/stops and
shutter speeds at any given ASA/ISO setting is essential. ASA/ISO stands for
American Standard Association/International Standards Organization, and is the
term used to designate baseline measurements of what used to be termed
"film speed", meaning specifically the film's sensitivity to varying
amounts of light. Rule number one relevant to ASA/ISO is the higher the ASA
number, the greater sensitivity to lower amounts of light in the environment.
These days, the term ASA/ISO remains relevant in digital
cameras in the same way. The only difference being that instead of having to
change a roll of film from one of a lower ASA to a roll with a higher ASA, one
may simply change the ASA setting by navigating through the camera's menus to
the ASA/ISO function, and simply dialing in the desired ASA speed.
ASA/ISO is important as a baseline measurement in attaining
correct exposure in any environment at any given f/stop and shutter speed,
because higher ASA's will allow for much smaller f/stop settings and longer
shutter speeds.
For instance, most people used to buy a roll of 24 or 36
exposure, ASA 100 film, pop it into their cameras and, say, go shoot the kids
at the beach on a sunny day. But another popular film was always ASA 400, which
is better for shooting indoors, because the film was more sensitive to the
obviously lower amounts of light indoor environments offer. The highest film
speed Mike and I shot with on the New Orleans was 3200 ASA, which is a film
speed that's very sensitive to low light conditions.
Using 3200 ASA film allowed us to go into a dark park in San
Diego, late at night, put the camera on a tripod to keep it still, open the
f/stop (again aperture) up to, say, f/5.6 (very wide, lots of light pouring
onto the film through the lens), set the shutter speed to, say,10 seconds
(meaning specifically that when the shutter release button is pressed to take
the photograph, the shutter will remain open for ten seconds), and though the
park was barely visible to the human eye, once the film was developed and
printed, the park would appear almost as if it had been shot during daylight
hours. Pretty neat, huh?
This example gives you a pragmatic understanding of the
meaning of "film speed", or ASA/ISO, and should help to clarify the
effect that higher ASA/ISO settings--available within all digital camera
menus--will have on the degree of sensitivity to low light conditions in any
environment. The highest ASA setting on my Canon 5D is a whopping ASA 12,000,
and the Canon 5D Mark II has an available ASA setting of ASA 25,000. The
cameras of the near future will probably make available an ASA setting of
ASA/ISO 100,000, such that you could shoot a park on a moonless night, with the
camera on tripod (again, to keep the camera perfectly still) set the f/stop to
f/5.6, set the shutter speed to 1/60th of a second, and despite not being able
to see your hand in front of your face, take a shot of a guy lighting a match
at 25 yards and, not only will appear as if it was captured during daylight,
the lit match will appear as a bright white streak. A good way to think of ASA,
is that ASA 100 registers light onto CCD’s at approximately the same baseline
receptivity of the human eye, while ASA 3200 (and all higher numbered ASA’s)
register light at the same baseline receptivity of a cat peering into the dark
of midnight.
3) Okay, now, on to the nature of f/stops. As I wrote
earlier, f/stops are simply incremental measurements of the opening of the iris
in all camera lenses, and specifically, they are precise measurements of the
diameter of this opening. The diameter of the opening is crucial in attaining
correct exposure, and also produces an effect which is called "depth of
field".
In addition to capturing "correct exposure, creating
varying "Depth(s) of field" is one of the primary functions of
f/stops. Depth of field is a term that defines the area, or the extent of the
subject matter, that is "in focus" within the field of view in front
of the lens, from the lens to infinity. The rule to remember relevant to
f/stops, is A) the wider the opening, or aperture, the smaller the f/stop
number, and the less depth of field, and B) the smaller the opening, or
aperture, the larger the f/stop number, and the greater the depth of field.
Said another way, A) Smaller f/stop number = shallow depth of field, and less
area in focus, and B) Larger f/stop number = greater depth of field, and more
of the subject matter in focus.
For instance, when shooting in a large field on a sunny day,
with trees very close to the camera, and also trees extending three miles into
the distance... at an f/stop setting of f/3.5 (very shallow depth of field),
when one focuses on a tree that is 20 feet in front of the lens, only that
specific tree will be in focus. Here’s the clincher: all the trees from the
lens to 18 feet away will be out of focus (or blurry), and all the trees
approximately 22 feet from the lens, out to infinity, will be out of focus. The
shallow “depth of field”, caused by using a wide open aperture (small f/stop
number) is also known in photography as “Selective Focus”, which is a
self-explanatory term.
Conversely, if one changes the f/stop to f/22, which allows
for a very long depth of field, or what we simply call an “excellent depth of
field”, then all the trees near the camera (say, one foot away) all the way out
to infinity, three miles away (and beyond), will be in sharp focus.
This should help you understand the nature of the term
"depth of field", and beyond this, f/stops are merely a way of
altering the amount of light falling onto the CCD, and achieving correct
exposure. Bear with me though, because it’s also crucial to understand that
f/stops, as I will explain, work in tandem with shutter speed and ASA/ISO
settings, in achieving “correct exposure”. And before I proceed, if the term
“correct exposure” still isn’t clear by example or implication, it simply means
a perfectly lit photograph, that isn’t either too dark, or too light. We all
know those photographs shot by well-intentioned Uncle Bob last Christmas that
are “incorrectly exposed” and are either so dark, Aunt Bessie’s face reads like
a gray-faced clown protruding from a bed of ash, or they’re so light (or “blown
out”) that Aunt Bessie looks like someone dropped 500 gallons of white paint on
her and the room in which she sits. And remember, Aunt Bessie likes both
correctly exposed photographs, and guns. ;-)
The final thing to remember about "good" depth of
field (depth of field in which all subject matter is in focus) is that it
begins at f/11. F/stop numbers higher than f/11 will produce excellent depth of
field; f/stop numbers lower than f/11 will produce imagery whose subject matter
is only partially in focus.
4) So let's move on to shutter speed. You now understand
f/stops are measurements of the diameter of the opening of the iris in all
camera lenses. You know that the smaller the f/stop number, the wider the
opening, the more light pouring onto the CCD, and the smaller the depth of
field. You know that the greater (or larger) the f/stop number, the smaller the
iris opening, the less light falling onto the CCD, and the greater the depth of
field. The first thing to remember about shutter speed is that these facts
concerning f/stops remains true at all shutter speed settings.
A shutter is simply a metal curtain within the body of the
camera, positioned between the lens and the CCD, that opens for a very precise
amount of time, and while open admits light onto the CCD. Shutter speed
settings, in most digital cameras currently made for the average consumer, vary
from approximately 1/3,000th of one second to 30 seconds. The basic rule to
remember wherein shutter speeds are concerned, is that fast shutter speeds stop
motion, or “freeze” motion in the physical environment that is being
photographed.
For instance, a very fast shutter speed setting of 1/3000th
of a second will freeze a humming bird’s wings in flight, such that the bird
appears as if it was floating in air, attached to an invisible string. At a
shutter speed setting of 1/60th of a second, the humming bird's wings will be a
blur. A key rule to remember about stopping motion in virtually all situations
(other than humming birds) is that a shutter speed of 1/250th of a second stops
motion. Humming birds are rarities, and require still faster shutter speeds to
stop motion. But, for instance, on the New Orleans, when shooting helicopters
rising off the deck, whose rotors were spinning at probably 2,500 rpm, shooting
at a shutter speed of 1/250th of a second made each rotor perfectly visible, as
if each blade was perfectly still, and the aircraft was floating inexplicably
in midair.
In low light conditions, such as your well-lit living room
at night, with five or seven, normal 75 or 100 watt, incandescent (tungsten)
light-bulbs, a shutter speed of 1/250th of a second is far too fast a shutter
speed, and far too short an amount of time to allow enough light to pour onto
the CCD and capture the correct exposure. Thus if you shoot a photograph in
your living room at 1/250th of a second, even at f/3.5, and an ASA of 400, the
image will be an underexposed, dark, black rectangle - in other words, you
won't have an image, unless you’re really into black rectangles. ;-)
Think of light as individual particles (photons) falling
through a lens onto a CCD. Physics, of course, also thinks of light as a wave,
but that's a discussion for another day. In the case of the light in your
living room at night, small amounts of photons travel into the camera lens and
onto the CCD. This small amount of photons requires the shutter be left open
for longer periods of time, so that enough photons have enough time to bombard
the CCD and create the image you see with your eyes. Too small an amount of
photon particles = not enough photons to create a correctly exposed photograph,
and the image will be dark. Too many photons (leave the shutter open for too
long) = too many photons to create a correctly exposed photograph, and the
image will be too light (too bright).
Usually, from my
experience, in a photographic exposure scenario, concerning an average sized
American living room, lit with, say, seven, 100 watt tungsten bulbs, the
correct shutter setting to capture the correct exposure at f/22 (excellent
depth of field), at ASA 100, is approximately 4 seconds to 6 seconds (on tripod).
Again, such a photograph can only be captured by setting the camera on a
tripod, because the human hand cannot hold the camera perfectly still for 4 to
6 seconds, thus without the tripod the image will be blurry.
Note that people moving around in the room, at that shutter
speed, will appear as ghostly streaks of blurred motion. Also note that it is
an accepted fact within photography that the slowest exposure speed for
photographs created by human, “hand-held” cameras, whose subject matter will be
in focus, must be captured at a shutter speed of 1/60th of a second or faster.
All shutter speeds above (or faster) than 1/60th of a second are captured so
quickly that the natural, slightly shaky human movement inherent to human
bodies, while hand-holding cameras, becomes less significant. That said, it
still remains true that if you set the shutter speed to, say, 125th of a
second, point it at a subject, and intentionally jerk the camera in any
particular direction while capturing the shot, you’ll achieve a blurry, out of
focus image. The same goes for images created while jerking the camera even at
a shutter speed of 1/250th. All of which is to say, that shutter speeds and the
results they achieve are based upon the presumption that the person who is holding
the camera and capturing the photograph is doing their best to hold the camera
relatively still.
Moving on...
In a room lit only by firelight from a well-lit fireplace, with the camera sitting perfectly still on a tripod, the shutter speed at f/22, 100 ASA, might well be approximately 30 seconds. Firelight is very low light, and does not emanate many photons, therefore, the shutter must be left open to allow that small a number of photons to stream into the lens, bombard the CCD, and create a correctly exposed photograph.
Now I think you're beginning to see how cameras think, and how they see, and how they record the world of light around us. Okay then, the next thing to understand is how these three, f/stops, ASA, and shutter speed, work together, and how changing any one of the three alters the other two, in achieving correct exposure. The hard science of photography is, of course, a highly logical, linear process, comprised of precise numbers and measurements, all of which correspond mathematically in exactingly predictable manners. In order to understand the incremental continuum upon which these linear inter-relationships occur, we must first understand the term “Equivalent Exposure”.
5) "Equivalent Exposure", is the primary rule, well-known to all professional photographers, which forms the baseline of all exposures, and begins by understanding what is called "The Sunny 16 Rule". This rule defines the correct exposure for shooting all, fully sunlit subject matter, on a sunny day, at noon, with no clouds, at an exposure setting of f/16, at 1/125th of a second, at ASA 100.
To understand the inter-relationships of f/stops, shutter speeds, and ASA, one must first memorize (or certainly at least understand) the standardized increments that define them. The point to bear in mind relevant to these increments, is that each of them is the precise equivalent of the increments on each of the other scales. When one increment changes, in order to maintain equivalent exposure, one of the other two increments on one of the other scales must be changed by the exact same increment.
And here they are:
The standard f/stops are:
f/3.5, f/5.6, f/8, f/11, f/16, f/22, f/32, etc.
The standard shutter speeds are:
30 seconds, 15 seconds, 8 seconds, 4 seconds, 2 seconds 1 second... 1/4 of one second, 1/2 of one second, 1/8th of one second, 1/15th of one second, 1/30th, 1/60th, 1/125th, 1/250th, 1/500th, 1/1000th... 1/2,000, 1/4,000, 1/8,000, 1/16,000th, etc.
The Standard ASA's are:
50, 100, 200, 400, 800, 1600, 3200, etc.
The “Sunny 16 Rule” states, that if you change the f/stop to f/11, which is one, full f/stop less than f/16, then in order to maintain the correct exposure, keeping the ASA at 100, we must change the shutter speed to 1/250th of a second. Why? Because changing the f/stop or aperture, to one that is even slightly more open (by only one f/stop) is therefore admitting more light onto the CCD. Therefore, in order to keep the same exposure, we must speed up the shutter speed making it remain open for precisely one half the time.
Now then. If, however, one wishes to alter the exposure, and for instance on a sunny day, shooting at f/16, at 1/125th, at ASA 100, and instead of shooting a subject upon which normal, full sunlight is shining, shoot a person sitting in the shade of a tall stand of trees, we must alter one of our three settings. The Sunny 16 rule is still applicable, however, the light falling onto the subject sitting in the shade beneath the trees is perhaps a full three f/stops less than the person standing in full sunlight. So, as in my previous examples of Aunt Bessie, if either the shutter speed, or the f/stop, or the ASA isn't changed, the person in the shade will be recorded as being very dark, and incorrectly exposed (by three full f/stops).
Taking into account the fact that adjusting the shutter speed three, full, equivalent increments to achieve correct exposure, while hand-holding the camera, would require a shutter speed setting of 1/15th of a second, using this option will create a blurry image. So obviously, scratch that. And let's say we want excellent depth of field because the trees behind the subject are quite beautiful. If we alter the f/stop three, full, equivalent increments to adjust the exposure and lighten the subject, we'll end at f/5.6, and this setting creates a fairly shallow depth of field. So scratch that as well. Given our objectives of creating a sharp (non-blurry) image, and one with excellent depth of field in which the trees are also in focus, two options are closed. But not to worry. We have one left. ASA. Alter the ASA setting three, equivalent increments to ASA 800, and voila! We have ignition, and a correctly exposed photograph, Houston! And if the subject in question, sitting in the shade beneath the trees was Aunt Bessie, we also avoid an unpleasant trip to the Emergency Room to have small pieces of lead removed from our fannies. Everybody wins!
I believe these examples and the definitions of the precise science behind them should be sufficient to help you and Amber begin to understand the essentials of photography. I wrote the first draft of this tutorial, technical essay last night, and edited it again as a second draft tonight. I pray you find it helps you both well. When it comes to this type of technical writing, I always like to give the finished piece a third polishing. But I didn’t want to leave you two hanging in the wind after promising to provide you a series of succinct, important insights into the primary essentials of the science, that can be difficult to find in any one book.
As I wrote last night, if you have any questions, sir, fire them at me and I will respond promptly.
All the very best to you, Amber, and your family!
Happy New Year, Charles!
Al
