Digital Photography: The Basics

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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.

About the author:

Loring Windblad worked as a freelance photographer for more than 20 years. He and his wife presently own and regularly use 1 VHS camcorder, 2 digital 8 camcorders and two digital still cameras. His latest business endeavor is at: http://www.santaclausca.com

Written by: Loring A. Windblad
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