Resolution
This term refers to the quality and clarity of an image. In the digital world it is generally measured in pixels. For printing, pixels per inch is the measurement (sometimes also "dots per inch," though the two are not identical in meaning). In the case of cameras, megapixels is the measurement. Resolution is the one of the most important aspects of any digital camera purchase.

When it comes to deciding what level of resolution is right for you, the biggest question you need to ask yourself is: "Am I going to want to print enlargements and/or crop and edit my photos before printing them at regular size?"

If you never print anything besides 4" x 6" pictures, a 2 megapixel camera should serve you just fine. However, if you would like to have the option to enlarge your pictures to 5"x7", 8"x10" or larger, consider a 3, 4 or 5 megapixel camera. This also holds true if you want the option to perform significant edits on your digital photos, such as cropping and resizing.

Basically, bigger is better when it comes to megapixels, although when shooting at higher resolution you will need more storage capacity as your image file sizes will be significantly larger.

CAUTION: Beware of the term "interpolated resolution." It refers to the camera's software adding pixels to the image after it is captured. Interpolated resolution is useful in some cases, but "effective resolution," which reflects the actual number of pixels in the camera's image sensor, is the most important for determining maximum print size and editing flexibility. Be sure you're comparing "effective resolution" when shopping for a camera or you may not get what you are really looking for.

Lenses (Optical Zoom)
Most mid-level and higher digital cameras have great zoom lenses. On digital cameras, optical zooms are measured by their magnification factor: 2x, 3x, etc. For comparison purposes, it is often easier to ask what the 35mm equivalent is. This is because the magnification measurements don't specify what size lens it is that's zooming.

For instance, a 2x zoom lens could mean a 28mm-56mm zoom, a 35mm-70mm zoom, or a 50mm-100mm zoom (expressed in 35mm equivalents). These lenses would all have different properties, so it is worth asking for 35mm equivalents to be sure you understand what you're getting.

CAUTION: Be sure to look for the "optical zoom" rating on a camera and not for the "digital zoom" rating, which can be much higher. Digital zoom merely crops away photo information and resizes the image, leaving you with a lower quality end product. Also, to get the most flexible zoom options, it is best to look for at least 4x optical zoom and then ask for 35mm equivalents.

Exposure Modes
Will the basic "automatic" mode suit your needs? Do you want shutter priority for sports? Aperture priority for portraits? Spot metering for difficult light. There's a real range of available features in this area, even on cameras of similar prices. Since exposure is the most important aspect of any photograph, you want to get as many exposure options as you can afford. Here are some particulars to look for:

• Shutter Priority
• Including fastest and longest speeds and whether bulb and time modes are offered
• Aperture Priority
• Including widest and narrowest
• Spot Metering
• Exposure Value Compensation
• ISO Settings
• Black and White Mode
• Noise Reduction
• This can be a critical feature for anyone considering long exposures and high ISO settings as important
• White Balance

Batteries
Digital cameras gobble batteries compared to film cameras. And the reason? Film cameras only need to open and close a shutter, advance film and occasionally charge a flash bulb. Digital cameras on the other hand must operate an electronic image sensor, LCD viewfinder, and image processor, and it is a lot of fun to regularly review photos onscreen after taking them.

This means you should give serious thought to the type of batteries a camera requires, be they AAs or a battery pack unique to your camera. Some pros and cons to consider include that standard AA batteries are readily available but require you to carry two sets of spares and throw more batteries out.

In contrast, camera-specific rechargeable battery packs usually last much longer, and you won't be adding more batteries to a landfill, but you will need to purchase at least one back up battery and perhaps a more sophisticated charger than comes with the camera.

Shutter Lag
Unless you are spending a significant amount of money on a digital SLR (single lens reflex) camera, you will likely notice a brief pause between when you press the shutter release button and when the picture is taken.

This pause is known as "shutter lag" and it can vary widely between different digital cameras. If you take sports shots or other action shots, try out a few cameras to make sure you'll be happy with the shutter responsiveness when shooting.

Click-to-Click Processing
Another important speed factor is the time it takes your camera to be ready to take another shot. This will vary depending on the photo quality settings you choose, whether you use a flash, and whether that flash is built in or not. Why the difference processing speeds? There are two main reasons.

First, the higher the quality of photo you take, the larger the image file that must be processed by the camera. In entry-level to mid-range cameras, it is rare to have a processor capable of reading and writing the largest image files the camera can generate in less than a few to several seconds. These processors are often up to the task of reading your lowest quality photos quite fast, but not usually the largest ones, especially if the camera is adding interpolated resolution to the file.

Second, built-in flashes often take a few to several seconds to recharge, because of the energy required. When you combine this energy requirement with the fact that a lot of energy is also required to process photo information and operate the camera's LCD screen the delay is not surprising. Often it can be avoided completely by using a good, off-camera flash that has its own energy source. To take advantage of this option, you will need to pick a camera with a flash shoe.

Viewfinders
When it comes to digital camera viewfinders, you should look at the following:

1. Does the camera have TTL (though the lens) viewfinding?

• TTL viewfinders are best because they are most accurate. With TTL, you get what you see, meaning the camera presents to you what is seen as it will be recorded.

2. What is the size and accuracy of the LCD viewfinder on the back?

• Larger LCD viewfinders screens are much easier to use and make it more fun to pass your camera around so photos can be reviewed and shared instantly. That said, they also consume more energy.
   
• On most digital cameras, your final photo will include less than what shows on the LCD viewfinder – anywhere from 2 to 15% less around the edges. At the upper limit, you will have to keep this inaccuracy in mind all the time and not crop photos too closely, which can be hard to remember.

3. What is the accuracy of the standard viewfinder?

• Some standard viewfinders on entry-level digital cameras can be significantly misaligned, while those on more expensive cameras can still be noticeably off. As with LCD viewfinders, take a few photos in the store with marker objects at the edges of the viewfinder and then compare by reviewing the photos on the screen to check for accuracy.

4. Is the standard viewfinder optical or a smaller LCD screen?

• In many cases you may want to turn off your LCD viewfinder to save battery power. You will get the best savings if the standard viewfinder is optical, rather than another LCD screen.
   
• Also, if you simply prefer to use an optical viewfinder rather than look at an LCD screen that gets blurry when you move the camera around, check to make sure you will have that option.

Image Sensors
There are two main types of image sensor, CCD and CMOS. While CMOS is quicker, it is usually associated with lower quality unless included in high-end digital SLR cameras. CMOS is also not widely available yet, so when shopping for entry-level to mid-range cameras, you will likely be comparing CCDs.

The most important questions regarding CCD image sensors involve resolution and physical size. When comparing CCDs, physically bigger is better for two reasons. First, because of the size of the pixels. Larger CCDs have larger pixels and larger pixels mean less noise due to a better signal to noise ratio.

Second, the larger your CCD, the more effective your optical zoom magnification becomes. Magnifying an image on a 1-inch square CCD 4 times is better than magnifying an image 4 times on a ¾-inch CCD.

Typically, CCD size is measured in the following ratios for entry-level and mid-range digital cameras:

• 1/1.5-inch CCD or 0.66 inch area
• 1/1.7-inch CCD or 0.58 inch area
• 1/1.8-inch CCD or 0.55 inch area
• 1/2.5-inch CCD or 0.40 inch area   
• 1/2.7-inch CCD or 0.37 inch area    

Memory Cards
The card that comes with your camera will be too small...period. Most cameras ship with an 8MB or 16MB card, while a 32MB card is the smallest you would want to have to be able to store a reasonable number of medium resolution images. Take this into consideration when purchasing and keep in mind that you'll want a larger card right away, so you won't have to stay near to your computer to download your photos when your card fills up.

File sizes will vary considerable depending on your camera's resolution capabilities and the quality settings you choose. However, in general, using the small memory card shipped with your camera will limit you to taking about the equivalent of a single roll of 24 to 36 photos at medium quality before you run out of space. The investment in a larger card, preferably a 64MB card or larger is definitely worth it.

Camera Size
Digital cameras with very similar features come in a real range of sizes, from ones as small as cigarette packs to ones as big as 35mm SLR cameras, which can be as bulky as a shoe box when packed with lenses attached.

Compact size usually comes with a higher price tag, so give some thought in this area before making a decision. Definitely consider a smaller camera if you think its size will make it more likely that you will bring it with you on outings.

Copyright 2005 ACD Systems Ltd. All rights reserved. Article used under license by Ipswitch, Inc.