by Arthur H. Bleich <firstname.lastname@example.org>
Since last year at this time, the winds of change have swept though the digital camera industry, blowing away most of the first generation failures and replacing them with a solid base of megapixel digital cameras that are a hair's breadth away from producing film-quality images. If 1999 looks to be the year you choose to become a digital photographer, this article will help you make sense of this often-confusing field.
I highly recommend that you check out the articles I published in TidBITS last year, as they cover many basic digital camera conventions, such as screen and print resolution, in more detail.
Resolution Recap -- When you begin researching digital cameras, you'll likely find yourself swamped by various numbers, such as pixel dimensions and image file sizes. In most cases, these refer to a camera's resolution, simply defined as the capability of a device to record fine details in an image, like individual threads in a sweater or separate grains of sand on a beach. Images from digital cameras (and scanners) are made up of little squares or rectangles called pixels. (Pixel is short for "picture cell" or "picture element.")
A digital camera's imaging surface is made up of rows of tiny individual light sensors (the sensor array) that capture color and light information, which is then electrically converted into digital data - the cells or pixels that make up the image. If a camera is capable of capturing an image that consists of 640 horizontal by 480 vertical pixels, it is said to have a resolution of 680 by 480 pixels, or 307,200 pixels (arrived at by multiplying the two dimensions).
The total sensor array is a charge-coupled device (CCD) and is used on most digital cameras now on the market. However, some cameras are being built around complementary metal oxide semiconductor (CMOS) devices, which are more reasonably priced and require very little power compared to CCD sensors. However, under certain conditions CMOS cameras sometimes produce undesirable electronic noise in the image.
If you can pack more pixels into a given area, you increase the resolution, which produces an image with finer detail. Think of it as using graph paper to help you draw a picture: the more squares per inch, the more nuances you can render.
If you want to make prints ranging from 5 by 7 inches up to 11 by 14 inches, consider buying a camera with as high a resolution as you can afford. Reasonably priced digital cameras are now available in the 800,000 to 1.6 megapixel range that will easily satisfy that requirement. However, if your images will be displayed on a monitor (or printed not larger than 4 by 6 inches), then a digital camera in the 640 by 480 range is all you'll need to accommodate the relatively low resolutions of most monitors.
Optical versus Interpolated Resolution -- Specifying digital camera resolution has become tricky lately, because some cameras offer both optical resolution, the actual number of sensors in the array, and interpolated resolution, a software-based method to increase the resolution of the optically obtained image by artificially adding more pixels.
Depending on the camera, interpolation can work well. For example, Agfa's PhotoGenie software, which comes with all but its lowest-priced camera, does an excellent job of interpolation when images transfer to your computer. You can also interpolate a picture from a low resolution camera within an imaging program, usually allowing it to be blown it up to a larger size without losing too much quality, depending on the quality of the original image. However, you can only interpolate (or "upsample") so much before your picture turns to pixel pudding, at which point no amount of digital manipulation can make it any better.
From Autofocus to Zoom -- Even though the terms are not unique to digital cameras, let's define autofocus and fixed-focus (or focus-free). Autofocus cameras automatically and accurately pinpoint whatever you aim at and record it as the sharpest object in the picture. Fixed-focus cameras have their lenses fixed (or locked) at an arbitrary distance calculated to keep most everything acceptably sharp from a few feet to infinity.
Because lenses used on digital cameras are of extremely short focal length, they have extraordinary inherent depth-of-field, allowing subjects both near and far to remain in focus, even when the lens aperture is wide open. So if your camera doesn't include an autofocus feature, it's no big deal unless you shoot big close-ups with a fixed-focus lens or expose without flash under low-light conditions (subjects or objects in the foreground may appear blurry). To compensate, some cameras feature settings to shift the point of focus manually, depending on whether you're shooting close-ups, portraits, or general subjects.
Finally, zoom lenses for digital cameras now come in two flavors: optical and digital. To make matters even more challenging, some cameras incorporate both. On a digital camera with an optical zoom, the resolution remains the same regardless of the focal length you choose. But a digital zoom uses only part of the sensor array and, unless it is interpolated, ends up exactly as if you'd cropped the image yourself - with resolution dropping accordingly. The Olympus D340L, for example, features a resolution of 1,280 by 960, but using the telephoto mode or the sequence shooting mode produces images that are only 640 by 480. Just remember: "Optical zoom, good; digital zoom, not so good," unless you shoot only for the Web or for CD-ROM multimedia productions, in which case it usually doesn't matter.
Recharge Your Batteries -- If rechargeable batteries don't come with the camera, I highly recommend getting some. Most digital cameras eat batteries like candy (the number one user complaint), especially since they must power the flash and the LCD screen used to preview and post-view shots (if the camera has an LCD). The best batteries I've found for most digital cameras are Quest nickel metal hydride (NiMH), made by Harding Energy and now sold everywhere.
Quest batteries hold a near-constant voltage when in use, and I've found they last four times longer than standard alkalines and at least twice as long as nickel cadmium (NiCad) batteries. And you can fully recharge them anytime, since, unlike NiCads (which photographers detest), they don't suffer from memory problems whereby they remember previous power levels instead of fully recharging. Although they can take up to 16 hours to recharge (from full discharge), Quests are so inexpensive (4 batteries and a charger for $35) you can buy several sets to always have enough on hand. If fast recharging is a must, a special charger has been promised soon.
For even longer-lasting power, I recommend one battery pack above the others. The Emberley ProPower 2.45, a featherweight NiMH rechargeable powerhouse that could put the Energizer Bunny into warp drive. Lasting more than twice as long as a set of Quests, it can double as an AC adapter, (which can cost as much as $65), and sells for about $99.
Storing Your Images -- Most digital cameras now use removable storage cards, with the two main types being either Compact Flash or SmartMedia. I've found them to be equally good, although presently Compact Flash cards have higher capacities. This can be a double-edged sword, though; it would be like using a roll of film that could hold 100 pictures, handy in one way but a little risky in that all your photographic eggs would be in one basket. Furthermore, it would take a long, long time to go through those images in the camera's playback mode if you had to. The main advantage to cards with more memory capacity is that they'll be able to store higher resolution images produced by the next generation of digital cameras.
SmartMedia cards are less expensive than their Compact Flash cousins and they can also slip into a FlashPath adapter ($99) can then be inserted into the Mac's floppy drive. Images then transfer faster than through a cable connection. (Don't confuse this capability with Sony cameras which use standard high-density floppy disks.) Both Compact Flash and SmartMedia are firmly established standards, so buy your camera based on its attributes and don't worry about the storage it uses.
Whether you store images on removable cards or the camera itself, you'll soon realize after transferring them to your computer that digital photos can quickly consume hard disk space. Higher-resolution images create larger file sizes.
Fortunately, many cameras allow you to select the degree of compression depending on the ultimate picture quality you require. On the Nikon CoolPix 900s, for example, available compression ratios are 1:4 (Fine), 1:8 (Normal), and 1:16 (Basic), with lower compression yielding better image quality than higher compression. In all modes, resolution remains the same. On some cameras, though, resolution also changes, so check the specifications. If a high degree of compression is acceptable, you can store more images in the camera or on its memory card. Expect to see compressed images grow from roughly five to twenty times in size if you open them in an image-editing application.
Also keep in mind that cameras compress the images using JPEG (Joint Photographic Experts Group) compression, which is a lossy method - some data is thrown out to conserve space. When you bring the image into your imaging program, save it as a TIFF-formatted file before doing anything. This eliminates the risk of it being closed as a JPEG file (which throws out more data) and becoming further degraded each time you save it.
Don't worry if you don't own an image-editing program such as Adobe Photoshop. Many digital camera manufacturers now include their own stand-alone programs that allow downloading to a folder, and some even have limited imaging capabilities. Another possibility is Adobe's cross-platform PhotoDeluxe, which is bundled with most cameras; other good software, like Microspot's PhotoFix (also bundled as PhotoStudio), should be given serious consideration. These programs are very inexpensive (under $100), easy to learn, require only a small amount of RAM and hard disk space to run, and have many features photographers will appreciate.
Until you pick the digital imaging program you want to marry - divorce not being an easy option in this field - you can do a bit of refining with those programs and then print your results. Some cameras, such as Epson and Olympus, allow you to bypass your computer entirely and print directly to one of their photographic quality printers, but in return for the convenience, you give up creative control of the final image.
Printing Images -- Although low resolution images are fine for the Web, printing them on paper changes things drastically. A 640 by 480 pixel image can be printed as an 8.8 by 6.6 inch photo, but the results could end up fuzzy or pixelated. If you want to print pictures as large as 5 by 7 inches, the camera should have 768 vertical pixels or more. Larger print sizes will usually require a camera with at least 960 vertical pixels (the vertical pixel number is the smaller one when resolution is described). However, some cameras with lower resolutions may be able to equal the results of those with higher pixel counts depending on the quality of their lenses and other design factors. Incidentally, many cameras offer a choice of high and low resolution modes. Use the higher one if you want prints, and the lower one for Web images or for sending photos as email attachments.
Into the Next Generation -- Digital cameras have now settled comfortably into their second generation. The 640 by 480 resolution cameras are mainly for snap-shooters who want to display work on the Web or make prints up to 4 by 6 inches. Megapixel cameras in the 1.2 to 1.6 million pixel range produce beautiful 8 by 10 inch prints (and larger) when output on inexpensive Epson 1,440 dpi PhotoStylus printers (the best, incidentally). The difference in resolution between 1.2 and 1.6 million pixels is often negligible.
Things improve every day. For example, some cameras can now even take multiple shots per second, whereas a year ago you would have been evaluating which camera had the shortest time lag between shots. (However, only a few, such as the new Olympus D620L can take multiple shots at their highest resolution settings - and you may still have to wait a minute or more after each half-dozen shots are taken for the camera to process the images.)
In the next installment of this article [which may have to wait a week or two because of Macworld Expo news -Adam], I'll offer my top picks for digital cameras currently on the market. Now that competition is heating up, there are some real bargains out there.
[Arthur H. Bleich is a photographer, writer, and educator who lives in Miami. He writes for major publications both in the U.S. and abroad, and is Contributing Editor of Digital Camera Magazine. He invites you to visit his Digital PhotoCorner, where you can find resources mentioned in this article, plus take an interactive course he'll be teaching called DIGIPHOTO 101.]