Understanding and Comparing Primary Features

What are some of the primary features to look at when comparing digital photography equipment?

Those features which are most commonly used to determine the best camera or camcorder in general are listed below. While these are far from the only features which can be considered, they cover the basic considerations of usability and image quality. Platform, connection type, memory and batteries directly affect the connection and after-sale cost of the equipment. The remaining eight features greatly affect the image quality and can be used to quickly compare two devices.

• Windows: Microsoft® operating system for PC computers.
• Macintosh: Apple® operating system for Apple computers.

• OS/2: IBM® operating system for PC computers
• Linux: Open source operating system for PC or Apple computers (not typically supported out of the box).
• Unix: AT&T® and Berkeley University for PC or Apple computers, primarily workstations (not typically supported out of the box).

Connection to a television or VCR for viewing or dubbing typically uses a composite video cable. Connection speed is standard, unless both the digital equipment and the VCR have a high-speed dubbing feature.

Connection to a computer for editing and sharing is typically done one of three ways:

• Infrared (IR): Infrared connection requires that the digital device has an infrared output and the computer has a digital input. Infrared connection uses these ports to convert the electrical information into an infrared signal, which offers moderate speed and eliminates the need for cables but which can be affected by interference from ambient light.

• Direct Cable Connection: A direct cable connection uses a particular cable type to physically connect the camera or camcorder to the computer.

• Composite Video Cable: If you have a video card with a composite video input, you can use the composite video output and a standard RCA patch cable to connect the camcorder to the computer. Speed will depend on the speed of the video card.
• Serial Cable: Offering the slowest cable connection speed, serial connection has the primary advantage that it uses an older port style which is found on most of the older computers (which may not have the newer port styles).
• USB Cable: Offers a fast connection speed using a port style commonly found on most computers sold recently. Most new computers will have at least one USB port built-in.
• Firewire: Using the IEEE-1394 standard, Firewire offers the fastest connection speed presently available. Because firewire ports are not yet standard on new computers, you may need to install a firewire port in order to use this connection type. A major advantage of Firewire connection is that it provides a perfect digital copy, without decompressing or recompressing the data, which occurs when the video is transferred as video rather than a digital signal.

• Memory Card Reader: A memory card reader allows you to plug the memory card from your camera or camcorder into a reader connected to your computer. There are three basic types, described by how they connect to the computer. The reader would need to be capable of reading the recording memory card used by your camera or camcorder.

• Parallel Port Card Reader: Slowest.
• USB Card Reader: Fast.
• PCMCIA Card Reader: Fastest.

• PCMCIA Cards: Short for Personal Computer Memory Card International Association, PCMCIA cards come in three types, with Type II and Type III being the most common.
  • Type I: up to 3.3 mm thick.
  • Type II: up to 5.5 mm thick.
  • Type III: up to 10.5 mm thick.
• CompactFlash: There are two types of CompactFlash memory card available.
• Type II: Type II CompactFlash cards can be used with multiple brands and types of devices and offers the highest maximum size of the memory types.
• Type 1: Type 1 CompactFlash cards can be used with multiple brands and types of devices. While they have a higher maximum size than SmartMedia cards, they are more limited in memory size than Type II CompactFlash.
• SmartMedia: SmartMedia cards can be used with multiple brands and types of devices. While they have a smaller maximum size than CompactFlash cards, they are also generally cheaper than CompactFlash cards.
• Sony® Memory Stick: The Sony Memory Stick offers a range of sizes. However, it is currently a proprietary media type and typically only used with Sony products.
• 3½" Disk: This was an early form of recording memory used in some cameras. It had the advantage of easy connectability. However, the memory limitation is a significant drawback. It was usually found on cameras offering a lower resolution.

• DV Tape: ¼" metal evaporate tape standard for recording high-quality digital video in NTSC format (United States) or PAL format (outside the United States). DV tape records significantly higher-quality video than other consumer video formats.
• MultiMedia™ Card: MultiMedia cards offer a high storage capacity in a remarkably small package, being about the size of a postage stamp. They are often used in camcorders designed with size as a primary feature.

• Premium Alkaline Batteries (AA, AAA): These will last the longest of the battery types. However, they are single-use and may be more expensive over the long run.
• Rechargeable NiMH Batteries (AA, AAA): These will not last as long as alkaline batteries. However, they generally have a higher capacity than high-capacity Ni-Cd batteries. The cost per unit is higher than alkaline, but the ability to recharge the batteries will make them less expensive over the long run.
• Rechargeable High-Capacity Ni-Cd Batteries (AA): These will typically have the lowest capacity of these three types. As with NiMH batteries, the cost per unit is higher than alkaline, but the ability to recharge the batteries will make them less expensive over the long run.

Pixel is short for "Picture Element" and refers to a point either in a display screen or in an image file. The display or image file is made up of a grid of these points. Increasing the number of pixels increases the clarity and quality of the image and increases how much the picture can be enlarged before pixelation occurs.

• 1280 x 960: 4" x 6" print
• 1600 x 1200: 8" x 10" print

• Optical resolution is an absolute number based on the number of pixels or photoelements in the image sensor. As the optical resolution increases, so does the amount of image information in the image file.
• Interpolated resolution uses software built into the camera to increase the number of pixels in the image by adding pixels based on the color and brightness of the pixels surrounding the new pixel. This is the same process used when editing the image using software on your computer. Using interpolation to increase resolution does not increase the amount of image information.

• TIFF (Tagged Image File Format): 24-bit image, no loss of image data
• GIF (CompuServe® Graphic Image Format): 24-bit image, image data reduced to a maximum of 256 colors.
• RAW: image output directly from the sensor, requires software designed to convert the image data
• BMP (BitMaP): up to 24-bit image, with each individual pixel mapped.

• JPEG (Joint Photographic Experts Group): 24-bit image, image data is averaged in blocks of  8x8 pixels.
  Note: The data is averaged each time the image is saved in this format, with a loss of image data each time. When working with JPEG files, you should save the file as few times as possible.
• DPOF (Digital Print Order Format): on-card format, which allows you to indicate which images should be printed from a storage card, using either a home printer or a printing service.
• EXIF (EXchangeable Image File): as JPEG, with the additional feature of storing extended camera information (time, date, ISO-speed, shutter speed, aperture, etc.) in the header of the JPEG file.

• CCD: The most common type of sensor is the CCD sensor (Charge-Coupled Devices). A CCD sensor contains thousands of photoreceptors which convert the light allowed in by the shutter to electrical data stored on the recording media or memory. CCD sensors are more reliable due to having been manufactured longer and are more sensitive than CMOS sensors.
• CMOS: The newest sensor type is the CMOS sensor (Complementary Metal-Oxide Semiconductor). CMOS sensors are cheaper and easier to produce and require less power than CCD sensors.

• Total Number of Pixels: This is the complete number of pixels on the sensor. However, not all pixels are actually used to record the picture. In order to get a correct image, the sensor needs the image data for a completely black pixels. To allow this, some of the pixels on the edge of the sensor are painted black.
• Effective Number of Pixels: This is the number of pixels actually available to record the image. This number more accurately represents the sensor's capabilities.

• Red-eye Reduction: This "pre-flash" reduces the red-eye effect by causing the pupils to dilate, which reduces the red reflection from the back of the eye.
• Flash Options: This refers to the number of flash settings (Flash On for all shots, Flash Off to never flash, Automatic Flash for the camera to determine whether a flash is needed, etc.).
• External Flash Support: Some higher-end digital cameras and camcorders allow you to connect an external flash, which in turn allows you a greater range of lighting effects.

• Focal Length: Simply speaking, the focal length is the distance from the center of the lens to the sharp image of a distant subject. Increasing the focal length narrows the angle of view, as with a telephoto lens. Decreasing the focal length widens the angle of view, as with a wide-angle lens.
• Autofocus type:
• Active autofocus uses an infrared signal to determine the distance to the subject.
• Passive autofocus calculates the distance based on the amount of light and the contrast in the subject.

• A digital or CCD shutter works by electronically limiting the sampling time of the sensor.

• A leaf shutter, or "iris" shutter, uses overlapping metal blades which can open and close to vary the size of the aperture. An illustration of the appearance of an iris shutter is given at right.

• A focal plane shutter uses two curtains to control the exposure. The first curtain exposes the film or sensor, and the second curtain moves after the first to cover the film or sensor.