Image Resolution and Memory Capacity

The first number you see in a digital camera description is its megapixel rating. A pixel (short for picture element) is one tiny colored dot, one of the thousands or millions that compose a single digital photograph. (One megapixel equals one million pixels.) You can't escape learning this term, since pixels are everything in computer graphics. The number of megapixels your camera has determines the quality of your pictures' resolution (the amount of detail that appears). A 5-megapixel camera, for example, has better resolution than a 3-megapixel one. It also costs more. How many of those pixels you actually need depends on how you're going to display the images you shoot.

1.2.1. Resolution for Onscreen Viewing

Many digital photos never get further than a computer screen. After you transfer them to your computer, you can distribute the images by email, post them on a Web page, or use them as desktop pictures or screen savers.

If such activities are the extent of your digital photography ambition, you can get by with very few megapixels. Even a $100, 2-megapixel camera produces a 1600 x 1200-pixel image, which is already too big to fit on the typical 1024 x 768pixel laptop screen (without zooming or scrolling).

1.2.2. Resolution for Printing

If you intend to print your photos, however, your megapixel needs are considerably greater. The typical computer screen is a fairly low-resolution device: most pack in somewhere between 72 and 96 pixels per inch. But for a printed digital photo to look as clear and smooth as a real photograph, the colored dots must be much closer together on the paper150 pixels per inch or more.

Remember the 2-megapixel photo that would spill off the edges of a laptop screen? Its resolution (measured in dots per inch) is only adequate for a 5 x 7 print. Enlarge it any more, and the dots become visible specks. Your family and friends will look like they have some unfortunate skin disorder. If you want to make prints of your photos (as most folks do), keep the following table in mind:

Table 1-1.

Camera Resolution

Max Print Size

0.3 megapixels (some camera phones)

2.25 x 3 inches

Camera Resolution

Max Print Size

1.3 megapixels

4 x 6 inches

2 megapixels

5 x 7 inches

3.3 megapixels

8 x 10 inches

4 megapixels

11x14 inches

5 megapixels

12 x16 inches

6.3 megapixels

14 x 20 inches

8 megapixels

16 x 22 inches

These are extremely crude guidelines, by the way. Many factors contribute to the quality of an 8 x 10 printincluding lens quality, file compression, exposure, camera shake, paper quality, and the number of different color cartridges your printer has, among other things. You may be able to print larger sizes than those listed here and be perfectly happy with them. But these figures provide a rough guide to getting the highest quality prints.

The other important advantage that a camera with multiple megapixels gives you is the ability to create high-quality prints of select portions of your photo. Say you've taken a great shot of your kids, but they occupy just a smidgen of the overall picture. No problemif your camera's got a lot of megapixels under the hood. Just crop out all the boring background and keep just the juicy parts (you'll learn about cropping in Chapters 9 and 10). If you try that same maneuver with a picture that comes from a 2 megapixel camera, you'll end up with a photo filled with unsightly pixels.

1.2.3. How Many Pictures per Card?

Instead of popping in rolls of film, you use a memory carda wafer thin sliver of reusable storageto store your photos on a digital camera. The memory card that comes with most cameras is a joke. It probably holds only about six or eight best-quality pictures. It's nothing more than a cost-saving placeholder, foisted on you by a camera company that knows full well that you have to go buy a bigger one. When you're shopping for a camera, it's imperative to factor in the cost of a bigger card.

Note: Most cameras come with three picture quality settings: draft, normal, and best quality (or, in the Starbucks-speak you'll often see in the camera's manual: normal, fine, and super-fine). Pick either of the two highest-quality settings if you plan on printing your photos.

It's impossible to overstate how glorious it is to have a huge memory card in your camera (or several smaller ones in your camera bag). Since you're not constantly worrying about running out of space on your memory card, you can shoot more freely, increasing your chances of getting great pictures. You can go on longer trips without dragging a laptop along, too, because you don't have to run back to your hotel room every three hours to offload your latest pictures. Your camera's battery life is more than enough to worry about: The last thing you need is another chronic headache in the form of your memory card. Bite the bullet and buy a bigger one.

UP TO SPEED The File Format Factor

Just about every digital camera on earth saves photos as JPEG files. JPEG is the world's most popular photo file format, because even though it's compressed to occupy a lot less space, the visual quality is still very high.

But JPEGs aren't the only format you'll run across, especially once you start editing your photos, which is covered in Part 3 of this book. While there are a zillion graphical formats known to computer-kind, there are really only two, besides JPEG, that you, the digital photographer, need to know about.

TIFF. Most digital cameras capture photos in the JPEG format. Some cameras, though, offer you the chance to leave your photos uncompressed on the camera, in what's called TIFF format. These files are hugein fact, you'll be lucky if you can fit one TIFF file on the memory card that came with the camera.

TIFF's advantage is that these files retain 100 percent of the picture's original quality. Note, however, that the instant you edit a TIFF-format photo, most image editing programs convert the file to the lesser quality JPEG format. That's fine if you plan to order prints or a photo book. But if you took that once-in-a-lifetime, priceless shot as a TIFF file, don't do any editingdon't even rotate itif you hope to maintain its perfect, pristine quality. Instead, make a copy of the file and use that copy when it's time to edit. Then hang onto the TIFF so you'll always have a master version of your original shot.

RAW format. Most digital cameras work like this: When you squeeze the shutter button, the camera studies the data picked up by its sensors. The circuitry then makes decisions pertaining to sharpening level, contrast and saturation settings, color "temperature," white balance, and so onand then saves the resulting processed image as a compressed JPEG file on your memory card.

For millions of people, the resulting picture quality is just fine, even terrific. But all that in-camera processing drives professional shutterbugs nuts.

They'd much rather preserve every last iota of original picture information, no matter how huge the resulting file on the memory cardand then process the file by hand once it's been safely transferred onto the PC, using a program like Photoshop Elements (coverage begins starting in Chapter 8). That's the idea behind the RAW file format, which is an option in many pricier digital cameras. (RAW stands for nothing in particular, and it's usually written in all capital letters like that just to denote how imposing and important serious photographers think it is.)

A RAW image isn't processed at all; it's a complete record of all the data passed along by the camera's sensors. As a result, each RAW photo takes up much more space on your memory card. For example, on a 6-megapixel camera, a JPEG photo is around 2 MB, but over 8 MB when saved as a RAW file. Most cameras take longer to store RAW photos on the card, too.

But for image-manipulation nerds, the beauty of RAW files is that once you open them up in a RAW-friendly image editing program, you can perform astounding acts of editing on them. You can actually change the lighting of the sceneretroactively! And you don't lose a single speck of image quality along the way.

Until recently, most people used a program like Photoshop or Photoshop Elements to do this kind of editing. But amazingly enough, humble, free programs like Picasa and EasyShare (both covered starting in Chapter 5), offer some RAW format capabilities.

Not every camera offers an option to save your files in RAW format. Why are only some cameras compatible? Because RAW is a concept, not a file format. Each camera company stores its photo data in a different way, so in fact, there are dozens of different file formats in the RAW world. Programs like Elements must be upgraded periodically to accommodate new camera models' emerging flavors of RAW.

The following table helps you calculate how much memory card storage you'll need. Find the column that represents the resolution of your camera, in megapixels (MP), and then read down to see how many best-quality photos each size card holds.

Table 1-2.

Camera Resolution

2 MP

3.3 MP

4.1 MP

5 MP

Card Capacity

How many pictures?

32 MB

30

17

14

8

64 MB

61

35

30

17

128 MB

123

71

61

35

256 MB

246

142

122

70

512 MB

492

284

244

140

1 GB

984

568

488

280

1.2.4. Memory Card Types

As the years go by, high-tech manufacturers figure out new and better ways to fit more pictures on smaller cards. If you were the first on your block to buy a digital camera, it probably used CompactFlash or SmartMedia cards, which now look gargantuan compared to, say, the xD-Picture Card. CompactFlash cards, on the other hand, have stayed the same size but greatly increased their capacity.

When comparing memory card formats, look at price per megabyte, availability, and what works with your other digital gear. The following list will help you compare the currently available card types.

CompactFlash cards are rugged, inexpensive, and easy to handle. You can buy them in capacities all the way up to 8 GB (translation: hundreds upon hundreds of pictures). Pro: Readily available; inexpensive; wide selection. Con: They're physically the largest of any memory card format, which dictates a bigger camera. A name brand 512 MB CompactFlash card costs less than $45.

• Sony's Memory Stick format is interchangeable among all of its cameras, camcorders, and laptops. Memory Sticks are great if you're already knee-deep in Sony equipment, but few other companies tolerate them. Pro: Works with most Sony digital gadgets. Cons: Works primarily with Sony gear; maximum size is 256 MB. A 128 MB Memory Stick starts at about $35, depending on the brand (Sony's own are the most expensive).

• The Memory Stick Pro Sony's newer memory card, is the same size as the traditional Memory Stick but holds much more. Sony's recent digital cameras accept both Pro and older Memory Sticksbut the Pro cards don't work in older cameras. As of this writing, you can buy Pro sticks in capacities like 512 MB ($45), 1 GB (about $65), 2 GB ($115), and 4 GB ($300).

• Secure Digital (SD) cards are no bigger than postage stamps, which is why you also find them in Palm organizers and MP3 players. In fact, you can pull this tiny card from your camera and insert it into many palmtops to view your pictures. Pro: Very small, perfect for subcompact cameras. Con: None, really, unless you're prone to losing small objects. 1 GB cards are now around $65 and 2 GB models are in the $100 range.

• The xD-Picture Card, tinier still, is a proprietary format for recent Fuji camera and Olympus camera models (see Figure 1-1). Its dimensions are so inconveniently small that the manual warns that "they can be accidentally swallowed by small children." Pro: Some cool cameras accept them. Con: Relatively expensive compared to other memory cards (256 MB = $35, 512 MB = $55, 1 GB = $75). Incompatible with cameras from other companies. Also incompatible with the memory card slots in most printers, card readers, television front panels, and so on.

Figure 1-1. The tiny Secure Digital card (middle) is gaining popularity because you can use it in both your digicam and palmtop. The even tinier XD-Picture Card (left) works only with Fuji and Olympus cameras. The larger CompactFlash card is still the most common (especially in larger cameras).

Some CompactFlash cameras can also accommodate the IBM Microdrivea miniature hard drive that looks like a thick CompactFlash card. For a while, 1 GB drives were popular with pros, but they're slipping in the polls now that you can get CompactFlash cards of up to 8 GB.

Tip: If you're shopping for your second (or third, or fourth) digicam, you may feel obligated to buy one that takes the same kind of memory card as the old one. Don't let the memory cards you've got limit your options. Memory cards are getting cheaper all the time; buying a new supply is not the big deal it once was. And since photo printers, card readers (Section 4.2), and photo kiosks now accept a variety of card types, you can, too.

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