Lesson 1: Camera Parts and Basic Terminology; A Primer

For my Treasure Quest friends who requested some photo lessons, here goes...

First things first
You must get to know the basic parts of your camera and some common terminology.  This isn't the fun and glamorous part of the photographic arts, but it is imperative that we have a common understanding of some basic terms and references or everything else will be difficult.

Disclaimer and Assumptions
Like almost all photo classes, this set of lessons will be built on the assumption that you have a digital Single Lens Reflex (SLR)camera, or at least a camera advanced enough to control aperture and shutter speeds.  A typical point-and-shoot will likely not allow you the control that a creative photographer will require.  You will also need a tripod.  Although a variety of focal length lenses is desired, I will try to avoid a need for specific focal lengths during the program.  There will be a couple assignments that explore the use of various focal lengths, but through the communal learning process we'll experience, it won't be necessary for you to go out and buy additional lenses.  (I'll just give you the ammunition to use on your significant other to try and persuade your argument for those capital expenses!)

Lens
Obviously, this is the optical part of the camera that focuses the image onto the film/sensor plane. In most of the point and shoot cameras, this is not an interchangeable item. For those more serious about photography, you need a camera with interchangeable lenses. Why? One size does not fit all! We'll get to more on that later.

There are a few important things to know from the start about lenses. The lens is arguably the most important part of the camera.  A poor lens will never yield excellent results -- maybe good or mediocre, but not excellent.  You're recording the light that passes through the lens.  During the process of recording the image, the one and only thing that stands between your sensor and the subject is the glass of the lens (and any filters you may put on the front of it). 

Lenses come in various focal lengths, some fixed lengths (primes), and some of variable length (zoom) capability.  In 35mm parlance (the old film size reference), a 50mm lens was considered a "normal" lens, rendering scenes generally as seen by the unaided eye.  Longer focal length lenses (telephotos) add magnification for rendering more distant objects with greater detail and shorter focal length lenses (wide-angle) allow compression of a broader cone of vision into the rendered image.  There are macro lenses that allow close up photography, micro lenses for really close up photography, and a variety of specialty lenses for special instances, such as tilt-shift lenses.  We'll discuss all these in later sessions.

You've maybe heard the term "fast lens".  How can a lens have a speed?  This reference is to the maximum aperture of the lens -- the ability of the lens to transmit light.  A "fast lens" is one that allows more light to pass through resulting in a faster (shorter) shutter speed under the same conditions as a "not so fast lens".  Sounds like mumbo jumbo, but this is key to future lessons.  This leads us to a discussion of  apertures and f-numbers, f-stops, etc.  We'll address filters later.

Aperture/F-number/F-stop
In photography, the lens aperture is typically specified as an f-number.  An f-number is the ratio of the focal length to the effective aperture diameter -- that's not too important in application so don't get overly concerned over the discussion to follow.  In application, much of this will become far more clear. 

Lenses typically have a series of marked/indexed f-numbers, or "f-stops".  One f-stop is defined as the square root of 2 change in f-number (e.g., going from f2.8 to f4 is one f-stop difference) and happens to correspond to a 50% reduction in transmitted light.   If a lens has a maximum aperture (f number) of 2.8, when the lens diaphragm (the light controlling function of the lens) is wide open, the amount of light transmitted would be twice that of a lens with a maximum aperture of 4.   What's important in application is understanding that a smaller number means more light coming through the lens, allowing for faster shutter speeds.  We'll come back to this principle in your first assignment towards the end of this lesson.  This will also be an area we will return to again and again throughout this "course".  Just note that the diaphragm within the lens is generally held wide open to allow the most light for focusing and viewing and must spring to it's set f-stop prior to the shutters firing to record the image.

Depth of Field (DOF)
The depth of field in an image is a descriptor of the range of distance in front of and behind the plane of focus that still yields acceptable resolution/focus.  An image with a shallow depth of field is characterized by a very narrow plane of focus, objects in the image just in front of or behind the focal plane appear soft or blurry.  An image with a high DOF is characterized by a very broad plane of focus with little of the image being soft or blurry.  DOF is dependent on both the magnification of the lens and the aperture.  Small apertures (high f-stops) yield increasing DOF, whereas open apertures result in increasingly shallow DOF.  Larger magnification lenses result in lower DOF at the same aperture than do low magnification lenses.

Mirror
On an interchangeable lens SLR camera, there is a mirror that diverts the imaged light passing through the lens up through a prism (to invert it so things appear right-side-up) and onto the focusing screen that is viewed through the viewfinder.  When the shutter release is pressed, the tell-tale click is in part, the mirror slapping up and out of the way of the light just before the shutters fire.  You've probably heard tell of "mirror-slap" -- the vibration that results from this movement -- causing image degradation.  For this reason, most higher-end SLRs will have a mirror lock-up feature that enables locking the mirror up prior to taking the exposure.  We'll explore this further at a later time. 

Shutters
Yes, I said "shutters".  The modern camera generally has two shutters unlike the single shutter cameras of old.  These focal plane shutters (I'm not going to discuss leaf shutters) are the timing device that controls the time the image sensor (or film) effectively sees the light passing through the lens. 

In their starting positions, the first shutter is closed, like the curtain before the play begins.  The second is actually open.  In a long exposure (greater than about 1/200th of a second), the first shutter opens -- for simplicity, let's assume it opens by lifting upward -- and after fully opening and the set exposure timing reached, the second shutter closes -- also by moving upward -- to again block the incoming light. 

The timing here is important.  As I noted, for long exposures, the first shutter opens and then the second shutter closes.  For short exposures, the second shutter follows the first, traveling at the same speed as the first, but before the first ever fully opens.  As a result, the sensor/film sees a traveling slit of light and the duration of which any section of the sensor/film sees the light is the set shutter speed, which may be less than  1/64,000th of a second!  The shortest shutter speed at which the full sensor is fully exposed between the first shutter opening and the second shutter closing is called the "sync speed" of the camera.  This gets important when we start to discuss flash photography.

Sensor/film, ISO and ASA
In the old days, cameras relied on film to record the image.  Various films had different sensitivities to light.  Slow films had a low ASA/ISO number, fast films, a higher number -- you can look up the definitions if you like, but they aren't too satisfying and not too important, really.  Slower films had an advantage of fine grain resolution, ergo better detail recording ability.  Faster films where characterized as grainy.  The trade-off was in the amount of light required to capture the image.  Faster films meant motion-stopping shutter speeds even in low light, whereas slower films meant longer exposure times.

The modern digital camera still has a sensor sensitivity setting and to a lesser degree, high ISO settings result in grainier images but for far different reasons.  The important thing to know is that changing the ISO setting of your digital camera by a factor of two (e.g., from 100 to 200) results in a one f-stop change in light sensitivity.  (Consider this: a scene is properly rendered into an image at an f-stop of 4, shutter speed of 1/250th of a second, and ISO of 200, to change the f-stop to 8 and keep the same shutter speed, one must change the ISO setting to 400.)

Metering
One can spend an eternity discussing metering and various metering modes of cameras and other devices, but for now, consider the basics.  Most things in this world, taken in aggregate, reflect about 18% of the light incident on them.  In black and white terms, this means they are gray.  Cameras generally use this principal in metering a scene.  We'll discuss this further in later sessions.  For now, read your camera manual to learn about the metering options and how to control them. We'll discuss some tricks of the trade for metering later.

White Balance
Digital SLRs have a function called white balance.  Simply speaking, this is a way to adjust the tonality of the picture to record the scene properly regardless of the lighting situation.  You may have noticed that not all light sources produce the same spectrum of light, i.e, they are of different colors.  The color spectrum of light produced by the sun is very different than that of an incandescent bulb.  Adjusting the white balance allows for the photographer to correct for the different color spectrum when taking the picture.  A whole lot easier than making the corrections in image editing software later!  We'll discuss the principals of making this correction at a later time.

Tripod
I think everyone knows what a tripod is.  Get one -- enough said.

Flash/Strobes/Hot Shoe/PC-sync
Everyone likewise probably knows what a flash or strobe is.  This is another areas we could spend sessions discussing, and we will spend some significant time in this arena.  Some of your cameras will have built-in flash/strobes.  Hopefully, they will also have a sync connection for external strobes.  Often, this will take the form of a "Hot Shoe", that place on the top of most SLRs that accepts a portable flash with one to five electrical connectors.  In some cameras, they may also have a PC-sync terminal to allow connection of a sync cord for flash.  If your camera has neither of these, we'll discuss what you can do to adapt to enable off-camera lighting.  In general, we'll discuss the flexibility that artificial lighting provides and the many ways to modify light.  Much more on this to come.


Enough rambling!  Since a picture is worth a thousand words, I want you to do a simple assignment.

Assignment 1
What you will need:

• Camera
• Lens
• Tripod (or a sturdy place to brace your camera for consistent images capturing the same scene repeatedly)
• Your camera manual
• Stationary 3-dimensional subject to photograph
• Constant ambient light (no flash except for steps 3 and 4, if desired)
• Creativity

Objectives:

• To force you to learn how to adjust your camera basic settings of aperture, shutter speed, and ISO.
• To make you aware of how these three settings inter-relate to produce an image.
• To begin to explore the effect of different apertures on the Depth of Field (DOF), that range of distance from the lens either in front of or behind the focal point that maintains focus within the image.
• To get you started experimenting with the basics of photography.

Steps:

1. With your camera in a set position, focus on a specific point of the object and take a picture with your widest open aperture (smallest f-stop), noting the shutter speed, aperture, and ISO settings.  This will be your reference picture.  You may have to dig through the manual for your camera to find out how to discover the various settings and controls.
2. Adjust your f-stop by closing it down two (or more) full stops.  You will have to increase your shutter speed by a factor of 4 (or more), or increase your ISO by a factor of 4 (or more) to accomplish this. With everything else the same -- same focal length, focusing on the same point, and from the same location -- take your second picture.  Compare it with the reference photo from step 1.  What is difference?  You should observe a difference in the DOF.
    
(NOTE:  Take a look at the distance scale on your lens(es).  On either side of the index mark, you may see one or more index lines, possibly with f-stop numbers like "32" or "8" associated with them.  These are not as common in modern auto-focus camera lenses as they were in their manual focus predecessors.  There used to be a full series of markings for various f-strops to each side of the index line.

 
A typical DOF scale from an old manual focus lens    

This was a tool for the photographer to use in determining the DOF.  A photographer would focus to the closest point in the image that he desired to have acceptably in focus, then to the farthest, each time noting where these points lit in the range scale.  Then the photographer would set the focus about 1/3 of the way from the nearest point to the farthest and set the aperture appropriately to yield the desired result.  Today, many cameras come with a DOF preview button.  Pushing the button will step down the lens aperture to the selected setting allowing you to preview the image as it will be rendered to the sensor instead of at the normal wide-open aperture setting.  In some systems, like the Canon EOS line, this button will also fire strobes in a sustained burst -- actually a series of very short high frequency bursts -- to increase the lighting for this operation.  If your camera has a DOF preview button, learn how to use it.)

3. Compose a photo exemplifying an aesthetic use of shallow depth of field (open aperture).
4. Compose a photo exemplifying an aesthetic use of deep depth of field (closed down aperture).
5. Share photos from 3 and  4 on the Lesson 1 thread on TQ.

An example image with a shallow DOF

An example of an image with a deep or high/large DOF

A walk in the snow

We finally got some snow, so out with the camera go I. Fighting bitter cold (sub zero temps, 30 mph winds) and wading in knee deep snow, the numbing cold tests my reserve as I strip my gloves to work the cold steel controls of my camera; I stalk the "essence of cold" amid the Jemez Mountains of Northern New Mexico. Thank goodness for the miracle thermal fabrics of today, providing warmth in an unforgiving environment as I practice my art.