Digital Camera Basics

By Joel Taylor

Digital Camera Basics... The Vocabulary

Shopping for a digital camera can be a difficult task considering the sheer number of choices out there. The number of manufacturers, models, and price ranges that need to be sorted out make the process difficult enough, but throw in all the buzz-words that need to be understood, and even a short list of cameras can become difficult to analyze.

This Tech Tip will take a look at a few key words that may come up when researching a digital camera, and will hopefully reduce the headaches associated with the process.

Pixels

Digital images are composed of thousands or millions of tiny squares called picture elements, or pixels for short. Each square has its own color assigned to it, and the compilation of all of these little colored squares allows for images to appear smooth when viewed at original size. If an image is magnified several times, the appearance of the pixels can become more obvious, and at high magnifications each colored pixel can be distinguished individually.

Megapixels

Basically, the term megapixel means one million pixels, and it is used to describe the maximum number of pixels found in an image produced by a digital camera. It is generally the criteria used to classify cameras, and checking the Geeks.com selection (http://www.geeks.com/products.asp?cat=CAM) shows that their cameras are all sorted into ranges of megapixels (MP).

Many people assume that because cameras are marketed so heavily by their megapixel specification, that this is the single most important criteria when choosing a camera. More megapixels do not necessarily equal better images, they mean larger images (both in physical size and in file size).

The megapixel count is achieved by multiplying the number of pixels in one horizontal line by the number of pixels in one vertical line. So, if a camera can produce images at a maximum resolution of 1600 by 1200 pixels, it is a 1.92 megapixel (1,920,000 pixel) camera.

It is not fair to assume that the images from the 5.0 MP Kodax CX7525 are automatically better than those from the 4.0 MP Kodak CX7430 strictly based on their megapixel count. All it means is that the maximum image size of the CX7525 is 2560 x 1920 and the maximum image size of the LS743 is 2408 x 1758. Many other features in the cameras can impact the quality of the images they produce, and may be far more important for the typical user to consider than the maximum overall size of each image.

Larger image size may do nothing for a user who only wants to view images on his computer screen, or for use on the web, but the higher megapixel images are important for those looking to make prints of their images. Generally, higher pixel counts in an image translate to the ability to create larger prints.

Sensors - CMOS and CCD

Digital cameras use a small sensor to capture the image before transferring it to flash memory for storage. Equivalent to a negative in a film camera, these sensors come in a variety of sizes, with most being between 20 and 40 millimeters squared. There are two types of sensors that may be found in cameras: CCD (Charged Couple Device) and CMOS (Complementary Metal Oxide Semiconductor). CMOS sensors are usually found in cheaper cameras and offer lower image quality than a CCD sensor that would probably be found in a more expensive camera.

There is an exception to the rule that CCD is better than CMOS, and that is with the Digital SLR-type (Single Lens Reflex) cameras. They use a much larger sensor (greater than 300 millimeters squared) and can provide excellent image quality, but the quality does come with a much higher price tag.

Zoom - Optical and Digital

Most digital cameras offer some sort of zoom, but it is important to identify which type is being provided. Optical zoom functions just as on a film camera, where the lens physically moves to produce the magnification. Digital zoom uses circuitry to enlarge a portion of the standard sized image and crops the content outside of the zoomed area. The quality of images produced using digital zoom suffer due to the nature of the process, and optical zoom is a far more desirable feature.

The price of a camera with optical zoom may be a good deal more than one with digital zoom, but the quality of the images cannot be compared. The Kodak CX7330 and the Kodak CX7300 are comparable cameras in many regards, but the CX7300 features only digital zoom, while the CX7330 features both optical and digital zoom for about $30 more.

Memory - Digital Film

The two important things to consider when choosing flash memory for a digital camera is that the right format is chosen, and that a quality module is chosen that can record quickly and be ready for the next picture as soon as possible. A photographer looking to snap a rapid series of high resolution images on their Kodak DX7440 has many options in SD (secure digital) memory to choose from but, they would be far better off with something like the SanDisk Ultra II SD card capable of a sustained write speed of 9 MB/s, than with a generic SD card capable of a burst speed rated at only 2.5MB/s.

Aliasing

Even if you think you know the basic definition of this term, it may seem confusing in the context of digital cameras. Aliasing refers to the appearance of jagged edges generally seen on diagonal or curved surfaces in images. This effect is caused by the fact that all pixels are square, and that even non-square shapes in an image need to be created with square components.

The solution to aliasing is not surprisingly called "anti-aliasing." Through software, the edges generally affected by aliasing are blended and the jagged appearance can be made much smoother. Video game enthusiasts may be familiar with anti-aliasing and the impact the varying levels of it can have on the overall performance of game play. Although the technology is similar, the personal importance of having the best digital images possible makes applying anti-aliasing just about a no-brainer.

Aspect Ratio

Aspect ratio describes the shape of a digital image, or any image for that matter, where the first number represents the width of the image and the second number represents the height. People may be familiar with the term as applied to televisions (as 16:9 wide screen televisions are now all the rage to replace traditional 4:3 units), and the concept is the same here.

Standard film cameras generally use an aspect ratio of 3:2, but most digital cameras have adopted a 4:3 aspect ratio so that images better fit on a standard computer monitor. Monitors with typical resolutions of 800x600, 1024x768, or 1280x960, for example, all have an aspect ratio of 4:3, so it only makes sense to produce images that will fit well on these screens. Although images can be manipulated to print on any size paper, special photo-quality paper is available to allow for high-quality prints to be made at the correct aspect ratio.

Connectivity

The pictures taken by a digital camera have to be extracted by some means in order to get them onto a computer, or perhaps directly onto a printer. In general, cameras provide a cable to connect to a computer either via serial, USB, USB 2.0, or Firewire.

Serial ports are just about extinct at this point due to their slow connection speeds and lack of plug-and-play support, but some older or lower-end models may still offer serial connectivity.

USB may be the most common form of connectivity, and if speed is important to you, look specifically for USB 2.0 support, as it is up to 40 times faster.

Some specialized cameras may take advantage of the high speed Firewire protocol for connecting to a computer. Just about all modern computers come with at least a pair of USB ports, but not all computers include Firewire. Firewire capabilities can be added to any computer with an available PCI slot by using an expansion card such as this one.

Some cameras don't require any cables at all, as they can transmit the images to a PC wirelessly. The Concord EyeQ is such a camera that utilizes Bluetooth technology in lieu of wires.

Even with all the modes of transmitting images listed so far, one other method may serve as a universal replacement for all of them. Many people find flash memory card readers to be a quick and convenient alternative to using the camera's native means of connecting. You simply remove the memory from the slot on the camera and pop it into the appropriate slot on the reader, and then the computer system can access the card like a local disk drive.

Final Words

Every high-tech field has its own set of specific buzz words, and digital photography is no different. Although by no means an exhaustive resource of digital photography terminology, this Tech Tip provides insight to a few key terms worth knowing in order to make shopping for a digital camera just a bit easier.