Digital Photography: The Basics
This information is Copyright January 2006 by
http://www.santaclausca.com and Loring Windblad. References for
this article include the author's personal knowledge and
experience, but also incude Digital Photography Quick Steps by
Doug Sahlin and other printed and internet sources. Additional
pertinent information compiled by Kathryn Whitaker
http://www.digital-camera-guides.com, T. J. Teirney
http://www.goldenirishlight.com, Ron Swerdfiger
http://www.purelygadgets.co.uk, Gary Hendricks
http://www.basic-digital-photography.com, Roy Barker
http://www.photographic-photography-resource.com, and Jack
Shafer http://www.jandmjewelrydesign.com is available and may be
found very useful. This article may be freely copied and used on
other web sites only if it is copied complete with all links and
text, including this header, intact and unchanged except for
minor improvements such as misspellings and typos.
You have decided on going digital. But it doesn't end there -
you go out and buy a digital camera and you're off and running!
You need to identify the kind of digital camera you are going to
make your first digital acquisition. To do this you need to know
what you are going to be using your digital camera for. You will
also have to consider what you are going to do with your digital
images. And your first step must be to learn a few basics of
digital photography to understand just what digital photography
is and how it differs from film photography.
To begin with, there are new terms relating to digital
photography you need to become familiar with. And there are
things you learned in film photography which still apply to
digital photography. Finally, most people relate their digital
photography to 35mm film photography; I certainly do. So here
goes.
Parallax: This deals with the relationship between "parallel"
and the resultant angles produced between the lens and the
photographic subject. You don't need to know or remember the
term parallax; what you do need to understand is that the closer
you are to your subject the more distorted the final
photographic result will be. Thus, if you are taking a picture
of a person from 3 feet away, the facial features could be
somewhat distorted; chubby cheeks, small ears, prominent nose;
versus taking the same picture of the same subject from 10 feet
away.
This effect is identical for both digital and film pictures.
Thus, if you want to take portraits you should be 10 feet away
using 3X optical zoom rather than 4 feet away with 1X zoom.*
This relationship corresponds to the same differences you would
get if you were using film and a 135mm lens at 10 feet rather
than a 50mm lens at 4 feet.*
Focal Length: Technically speaking, for a thin double convex
lens, all parallel rays will be focused to a point referred to
as the principal focal point. The distance from the lens to that
point is the principal focal length f of the lens. For a thick
lens made from spherical surfaces, the focal distance will
differ for different rays, and this change is called spherical
aberration. The focal length for different wavelengths will also
differ slightly, and this is called chromatic aberration. The
most important characteristic of a lens is its principal focal
length; related to 35mm film photography the typical "standard"
focal length is 50mm to 55mm. Most digital camera focal lengths
will be compared to film camera focal lengths.
As an aside, the inverse is used most often in optometry and is
called the lens strength or lens "power". Optometrists usually
prescribe corrective lenses in terms of the lens "power" in
diopters and both telescopes and binoculars are rated in "power"
also.
Pixels: In film photography we deal with round "dots" of color
or shading. In film photography we say a picture is "grainy" -
meaning we can see the individual dots. In digital photography
we deal with square "pixels" of color or shading. We say that
the picture is "pixielated" or "out of focus" when we can see
the effects of the individual "squares" of color or shading.
Megapixels: Megapixels refers to the number of pixels contained
in 1 square inch of photographic information. It stands to
reason that the more pixels you can get inside your 1 square
inch the smaller those pixels will be, thus the higher your
resultant resolution (the better your focus) will be. However,
this is only part of the "resolution" equation.
Focus: Focus deals with two very related concepts: In film
photography it is concerned with the "fineness" of the film
(size of the dots) coupled with the "quality" of the lenses. In
digital photography it is concerned with the "number of pixels
per square inch" (size of the squares) coupled with the
"quality" of the lenses. 10 million pixels per square inch
should provide higher resolution than 1 million pixels per
square inch? But if it is coupled with poor quality lenses you
could get better results from a high quality lens on a
1-megapixel camera. In film photography "camera cost" is
generally related to "lens resolution"; in digital photography
"camera cost" is generally related to both "image resolution"
and "megapixels per square inch". In digital photography "image
resolution" is expressed as "X ppi".
Boiled down to layman's terms, "image resolution" is a product
of "focal length" and "color correction". Remember the
discussion above concerning the focal length of a given lens
having both spherical and chromatic aberration? It is the
"chromatic aberration" with which we are concerned here; the
ability of a lens to "focus" all wavelengths (colors) at its
primary focal length. This is lens quality. So when you purchase
your digital camera you should make your decision based upon
both "megapixels" and "image resolution".
JPG, JPEG: This is the "coding" standard which refers to digital
still images as put forth by the Joint Photographic Experts
Group (JPEG). Their web site, and information on standards, is
located at http://www.jpeg.org/.
MPG, MPEG: This is one of two major standards for digital moving
images as put forth by the Moving Picture Experts Group (MPEG).
Additional information on MPEG-1 (Video CD and MP3), MPEG-2
(Digital Television and DVD), MPEG-4 (multimedia for fixed and
mobile web) MPEG-7 (description and search of audio and visual
content) and MPEG-21 (multimedia framework) can be found at
http://www.chiariglione.org/mpeg/.
AVI: This is "Audio Video Interleave. It is a special case of
the RIFF (Resource Interchange File Format). AVI is defined by
Microsoft. AVI is the most common format for audio/video data on
the PC" as found at
(http://www.jmcgowan.com/avi.html#Definition).
SLR: This is Single Lens Reflex, which means that when you look
through the viewfinder you see exactly what the picture is going
to be, whereas if you see the framing through a separate
viewfinder your exact picture will be slight offset from the
framing of it you see through the viewfinder. In a long-distance
landscape it generally makes no difference but in a close-up
portrait or snapshot it could mean cutting someone's head off at
least partway.
Digital Picture Preview: This displays a digital image on the
back of your digital camera which fairly corresponds with the
image you would see with an SLR camera - that actual picture
that you will be getting as opposed to a view through a separate
and offset viewfinder window.
These are the basic things you need to understand about
photography in general and digital photography in particular
before you decide to purchase a digital camera. It helps to
understand that most digital cameras come with either MPG or AVI
video image capability but that SLR digital cameras do not have
digital video capabilities. It also helps to know that AVI video
format is more easily edited than is MPG video format, but that
both can come with built-in Audio tracks.
What you need to understand about your "built-in" audio track,
however, is that your audio volume will be very low, actually
too low unless you are very careful. However, you can, when
composing a video presentation, use "silent" MPG or AVI footage
and add a soundtrack recorded separately. This is very easy to
do if you have a computer with Windows XP SP2, which comes with
both a sound recorder (it came with all versions of Windows) and
a Windows Movie Maker.
You can see examples of the audio level problem and solution if
you view both video presentations at
http://www.santaclausca.com.
The final pieces of choosing your digital camera are determining
just what you are going to use the camera for and how much money
you have available to invest in your camera. Your considerations
should be 1) your purpose for using the camera, 2) quality of
product (particularly the lens), 3) megapixel rating of the
camera and 4) buy the best camera you can afford.
* - refer to my next article, Digital Photography: Choosing Your
Camera.