Ottawa PC Users' Group, Inc.
 Product Review


PRODUCT REVIEW
Choosing a Digital Camera
 by Michael Murie

If you've upgraded to Easy CD Creator 5 Platinum or Toast 5 Titanium (you have, haven't you?), maybe you've begun to explore the new VideoCD creation features, which include making slide and movie shows, and perhaps you've played with the new versions of Photo Relay (in ECDC) or iView Multimedia (in Toast), which let you make family photo albums and much, much, more.

While you can used scanned-in photos for either task, a digital camera will greatly ease the process. With a digital camera, you can just hook it up directly to your computer and download the pics, no scanning necessary. Also, the quality of the images produced by digital cameras has improved so much that many people are finding that they don't use their film cameras any more.

Fortunately, it's a great time to buy a digital camera. The cost is coming down, the image quality is going up, and there's a wide range to choose from. If anything, there are almost too many to choose between. And digital cameras still aren't for everybody. So here's a guide to help you decide if it's time to buy, and if so, what features you should look for.


Advantages of Digital Cameras:

Computer friendly: They are the best way to get images onto a computer for use in Web pages, CDs, and e-mail. You can make your own albums, or just distribute individual photos to friends and relatives. No film and paper costs: Until you print them, images cost virtually nothing (and wasted photos can be deleted for nothing).

Editable: With a printer and image editing software you can edit and print to any size. Editing can involve anything from color correction to compositing one or more pics into one.

Review: With the LCD display included on most cameras you can review the picture right after it's taken, and be sure that you got a good picture before it's too late to take another one.


Disadvantages:

You need a computer: While it's possible to store and print pictures without a computer, it's not yet easy and convenient to do so. But if you're reading this newsletter, we assume you have that base covered!

Expensive: A good digital camera is still expensive compared to a film camera of comparable quality. But prices are coming down, and with no film or developing costs, digital cameras can be cheaper in the long run, depending on how many pictures you take.

Higher per-print cost: Printing costs may actually be higher (if you print every picture) but if you find you only print one or two pictures (and send the rest via CD or e-mail) then you will save money.

Longevity problems: While inkjet printers can produce photo- quality images, the prints may not last as long as traditional prints. New archival papers have come out to address this issue.

Low light sensitivity: Film is available in a wide range of speeds (up to ISO 1600 or higher) Digital cameras tend to be slower, and images get noisier when pushed. Also, digital cameras tend to have noise problems when used for very long exposures.

Once you've decided to buy one, it's time to start looking at the different features and functions. With such a variety to choose among, you need to determine how much you want to spend, and what features are important to you. Let's look at the major features you should consider when looking at cameras. But it doesn't cover some of the extras you might find important, such as the ability to capture video sequences, or audio along with pictures. So it still behooves you to check out several cameras in your price range.


Cost

How much do I need to spend? The answer to that should emerge after you determine what resolution you need. Digital cameras with a resolution of 2.1 million pixels cost about $500, while top-end 3.1-megapixel cameras cost $700-$1,000 (US). Prices will continue to come down as resolution improves.


Resolution

What is resolution? For digital cameras, resolution is defined as the number of pixels in the image produced by the camera. You'll hear terms like 2.1 megapixel, where megapixel means millions of pixels. In their literature, manufacturers often refer to the number of pixels in the CCD (picture-taking element), which can be different from the number of pixels in the images recorded. The Nikon CoolPix 950, for example, is advertised as a 2-megapixel camera, though the images it produces are 1600-by-1200 (1,920,000 pixels.) This difference is due to masking and other issues which reduce the number of physically usable pixels. Some cameras actually enlarge the images they capture using interpolation, and the manufacturer will quote this enlarged number, even though the image has a lower actual resolution. How many pixels is big enough?

Here, the first question is what do you want to do with the images? If you want to use them for display on a computer screen only; for example to e-mail to friends, or to place on CDs and web pages, then you probably want an image from 640-by-480 to 1024-by-768 (the size of most screens). Even if that's the case, I'd still recommend getting a slightly larger camera (a 2.1 megapixel) just for the increased flexibility. With a larger image you can crop or reduce resolution easily, but you can't go the other way.

For printing, resolution is more complicated. What size image do you typically print? 4-by-5 or 8-by-10? After determining this you have to do a calculation to determine what resolution you need, based on the printer you are using.

As an example, the popular Epson Stylus Photo printer prints at 720 dots per inch. But you don't need to send the printer an image that is 720 pixels per inch (ppi). This is because the printer uses solid colored dots (cyan, magenta or yellow) at each dot, whereas each pixel of the computer image can be any one of 16 million colors. So if you send a 720 ppi image to a 720 dpi printer you'd be throwing away color data. The best sizes to send to the printer are either 360 or 180 ppi. Better images are produced if you use an even divisor of the resolution of your printer for the image you are printing (i.e. 720 divided by 2 or 4). So, if your printer is 600 dpi, use 300 or 150 dpi images.

Divide by 2 or 4, which is best?

Here's where it becomes a tradeoff between detail and performance. You will see a marginal difference between printing a 360 ppi image and a 180 ppi image on a 720 dpi printer (or between a 300 and 150 ppi image on a 600 dpi printer.) There will be some detail differences between images because sudden changes in brightness will be more accurately rendered in the 360 image than in the 180, but the color differences will be marginal. However, with the larger image it will take you longer to manipulate and print. So do a test first on your printer to see the differences, and then decide which resolution you prefer. Once you know which size you want, multiply the image size by the resolution:

10 inches x 180 dpi = 1800

8 inches x 180 dpi  = 1440

So to print an 8 x 10 you'd ideally like to have a 1800-by- 1440 pixel image. A 1600-by-1200 resolution camera produces images that are a little smaller than ideal. Still, it's 'close.' And if you only print 8-by-10s occasionally, probably fine for most purposes. If you prefer 360 dpi images, however, you should get a 3-megapixel camera.

A little-considered issue is the other meaning of the word resolution: the ability to capture fine detail. Two cameras producing the same image size might produce very different quality images. In other words, you might be able to see smaller changes in the image in one picture versus the other. This is different from being able to zoom in closer to see more detail. Image quality can be affected by the quality of the lens, any manipulation done by the camera (rescaling and color calculations) and the compression used on the image.

Most cameras use some kind of compression, typically JPEG, when saving the images. Most cameras have two or more different compression options (high, medium, or low quality, for example). No matter which setting you use, the resulting image size in pixels remains the same, but the file size (in kilobytes) will be smaller for the more compressed images (low-quality). To compress the image, resolution (detail) is thrown away. Of course, the more compression used, the more images you can capture before the memory card is filled. Again, you should experiment with your camera to determine which compression choice gives the best detail, versus an acceptable number of images captured. You can always buy a larger memory card if needed.

Lenses

Optical Zoom

Most cameras feature some kind of zoom lens. It's important to distinguish between optical and digital zoom, however. An optical zoom uses lenses that move to scale the image (technically speaking, the focal length of the lens is being changed), whereas a digital zoom scales the image electronically, without actual additional picture information. There is therefore a big difference in quality between these two techniques. Optical zooms are always preferable, although many cameras offer a combination of both, using optical up to a point, then switching to digital.

When comparing lenses, we are most interested in the field of view of a lens (how wide or narrow the lens is.) Unfortunately, historically the focal length of the lens has been used as an indication of the field of view of a camera. For 35mm cameras, a 50mm is considered a "normal" lens, 28mm is considered "wide" and 150mm is a "long" lens. This measurement is based on the size of the image (in the case of a 35mm film camera, it's the film size), but in the case of digital cameras, the CCD chip is much smaller (in some cases 1/3 or 1/2 an inch.) So focal length is different. Since more people are familiar with the measurement for 35 mm cameras many digital camera manufacturers actually quote the range of a lens focal length converted to a 35mm camera equivalent.

The most common optical zoom lenses are 2X and 3X. A 3X means three times from widest to longest lens setting (i.e., 38mm to 120mm is a 3X, 38mm to 75mm is a 2X) There are a few cameras that come with long lens, a 6X or 10X. However be aware that as the lens gets longer, it gets more difficult to hold the lens steady enough while the picture is being taken. One manufacturer includes an image stabilization system in their long lens camera precisely because of this problem.

Digital Zoom

A digital zoom is software in the camera that "zooms" the image by scaling it. Essentially it does the same as what happens when you use an image editing application to enlarge an image. In its simplest form, to double the size of an image, the software duplicates every pixel. Ideally, the algorithm will average two adjoining pixels to create the new extra pixel; this is called interpolation.

Digital zooms aren't usually continuous: you can't zoom smoothly from one focal length to another, as with optical zoom. Instead, the zoom jumps from one multiple to another. The most obvious is 2X, which is multiplying each pixel by two. The real problem with digital zooming is that it doesn't really do much more than can already be done with a software application after the picture is transferred to the computer. It really just increases the file size in the camera unnecessarily, using up valuable memory card space.

So, consider a digital zoom only as a nice-to-have feature, and go for an optical zoom whenever possible.

Macro

This is the ability of the lens to focus on objects that are very close to the lens. Even with a zoom lens, if you want to take a close-up of an object, and the lens won't focus on something closer than four feet, you won't be able to fill the frame with a postage stamp. So if you plan to take close-ups you will want to make sure the camera has macro capability.


Bottom Line:

Define your needs!


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Ottawa Personal Computer Users' Group (OPCUG), Inc.
3 Thatcher Street, Ottawa, ON  K2G 1S6

The opinions expressed in these reviews may not necessarily
represent the views of the OPCUG or its members.