Digital Photo Myths Dispelled

Megapixels, Web accelerators, batteries, memory cards, and more.

Dave Johnson

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Feature: Digital Photo Myths Dispelled

There's a common perception that we as a society have become jaded and cynical. People don't accept anything at face value; and they rarely believe what they hear and read. Ironically, that's just another myth we choose to accept. After all, we all know someone who has been duped into believing urban legends about imminent e-mail taxes, a pet being microwaved by accident, or a $250 Neiman Marcus cookie recipe. I submit that not all of us are quite as cynical as we may believe.

So I've been thinking: Are there some common digital photography myths that need busting? What common-sense, seemingly obvious digital truisms need to be exposed for what they really are--myths? This week, let's do some debunking!

"All 3-Megapixel Cameras Capture the Same Resolution."

A casual inspection of the shelf at any camera shop will reveal a wide selection of seemingly identical 3-megapixel digital cameras. Likewise, there are many cameras that boast 4, 5, and 6 megapixels.

But cameras that boast the same number of megapixels don't necessarily give you the same resolution. Even if you set aside optics and other differences that affect picture quality, they simply aren't always providing the same number of pixels. It can be helpful to read the fine print on the box, since pixels can be measured many different ways.

Some cameras advertise the total number of pixels on the image sensor, only a fraction of which are actually used to take the picture. A better measure is the effective pixels, since that's closer to the camera's "real" resolution--but even that number includes pixels that have nothing to do with imaging. The output pixels are what end up creating your final picture. But that number can be very different than the actual number of sensor pixels--consider, for instance, FujiFilm's SuperCCD technology that creates 6-megapixel images from 3-megapixel sensors.

Bottom line? If you're comparing similar cameras, read the specs to see how the manufacturers describe the pixel ratings. That way you don't try to compare effective pixels to total pixels, for instance. Personally, I think that effective pixels are the most accurate measure of resolution--so try to use that rating to make apples-to-apples comparisons.

"A 6-Megapixel Camera Is Twice as Good as a 3-Megapixel Camera."

While there are other factors to consider than just the sheer number of pixels, I will agree that more is usually better than less. If I had a 6-megapixel camera, I could make larger, sharper prints than I could with a 3-megapixel camera. But 6 is not twice as good as 3--not in the sense that I can make a print that is magnified by 2X.

The reason is that megapixels measure potential area, the length of a picture multiplied by its width. So consider a typical 3-megapixel image, which measures 2048 by 1536 pixels. At 300 dots per inch, that's a 5-by-7-inch print. A 6-megapixel image measures 3000 by 2000 pixels and can print at about 7 by 10 inches. So the 3-megapixel image isn't magnified by a factor of 2--that would result in a 10-by-14-inch print.

"An Internet Accelerator Will Speed Picture Uploads and Downloads."

There was a time way back in the mid-nineties when people upgraded their modems to get faster performance. By the late nineties, though, the 56-kilobits-per-second modem represented the fastest way to send information through traditional phone lines. And it still does.

If you want to share digital photos via e-mail and the Web, get a broadband connection like DSL or cable. The Internet accelerator software commonly advertised on television and on the Internet can't make your 56-kbps modem go any faster--it's already pushing the phone lines to their theoretical speed limit. All that accelerator programs do is cache Web pages to make Web surfing seem faster.

"NiMH Batteries Don't Suffer From the Memory Effect."

Nickel cadmium batteries, which were the most commonly used rechargeable batteries in portable devices a dozen years ago, were subject to something called the memory effect. If you consistently topped off a NiCD battery when it was only partially discharged, the battery would quickly lose its full original capacity. To mitigate the memory effect, manufacturers recommended that you regularly run your battery completely down, then recharge it.

Nickel-metal hydride batteries, which succeeded NiCDs in many applications, were originally thought to be free from memory-related problems. It didn't take long, though, for users to find that NiMH batteries suffer from their own memory issues. Technically, it's something that engineers call voltage depression--but the effect is basically the same with NiCD batteries (though it's not as severe). To avoid NiMH memory loss, you should fully discharge these batteries once every six or ten uses.

But there is good news: Lithium ion batteries, used by many new digital cameras, are free of memory-related problems. They also hold a charge better over time, so that you can expect to pick up the camera you charged up last week and expect it to have a virtually full tank. The older NiCD and NiMH batteries lose their retained charge fairly quickly--even if they are not being used.

However, no rechargeable battery is free from the degradation that comes with use over time. You'll eventually find that the number of shots you can take per charge has dropped to about two-thirds or less. If you use your camera regularly, you'll likely have to buy a new set of batteries once a year.

"Removable Memory Cards Are Damaged by Airport Security Measures."

The digital camera and memory card industries agree that memory cards--and the pictures stored on them--are 100 percent safe from damage by metal detectors in airports. And I generally stand by that assessment, since I've flown with my digital camera dozens of times with no ill effects.

But I'm slowly changing my opinion on this one. Recently, a number of PC World readers have sent me letters complaining that their cards have seemed to die after passing through airport screening systems, which include both metal detectors and X-ray machines.

I believe that X-rays and memory cards get along just fine. However, I'm willing to admit that the jury is out on the new high-powered metal detectors: They may be affecting digital photography hardware. I'll let you know if the major card manufacturers change their stance on the effects of airport security measures on their products.

Bottom line? If you're paranoid, ask for a hand check.

Dave's Favorites: Share Your Photos With Hello

Sharing your digital pictures with friends and family can be something of a hassle. Copying images to CD is time consuming, and sending them by e-mail can be confusing. My dad, for instance, is new to computers and doesn't appreciate having to resize photos so they'll "fit" in e-mail. I recently discovered Hello, a terrific alternative to both of those options.

Hello is a free instant messaging and picture sharing tool from the same folks who make the Picasa photo organizer. After a few of your buddies sign up for Hello, they'll appear as Friends in the program's main screen. Just click on a Friend and start chatting. Or click the Send Pictures button to shoot pictures from your own computer to any of your correspondents. You can send one or more pictures to an individual, or blast them to several people at once.

And it gets better. Hello makes it easy to chat about your pictures, because all the images you and your Friends are sharing appear as a filmstrip on screen. Click a picture and type a message; your buddy sees the picture and text together, so you can explain your vacation pictures, for instance, in an online chat.

Hello is brilliantly designed. I needed no help getting up and running, and I was sharing pictures and chatting just minutes after installing it.

Q&A: How Many Pixels Is Enough?

I am new to digital photography and want to take pictures to share via e-mail and print--usually at 4 by 6, but sometimes as large as 16 by 20. Right now I have 200 slides scanned in TIFF format. My question: How big is too big from a practical perspective? My 200 slides now take up about 12GB. Should I save the scans at this size or should I resize the files before I save them? If I downsize the files, what size would you recommend? I am still very confused about dpi and pixels.

--Dale Walker, Huntsville, Alabama

That's a great question, Dale.

Some people--especially photo-purists--may disagree with me, but I think you're wasting a lot of space by keeping the images in TIFF format. I frequently scan my old 35mm slides; at top resolution in TIFF, they consume about 50MB each. If I save the same file as a JPEG set to its very highest quality level (moving the quality slider to 99 or 100 in Jasc Paint Shop Pro or Adobe Photoshop), the picture only takes up 6MB. That's about 10 percent of the original size, and the difference in quality is essentially imperceptible.

I'd rather that you switched from TIFF to JPEG than reduce the pixel size of the images, since you'll need all those pixels if you want to make 16-by-20-inch prints. You'll want to send 300 pixels per inch to your ink jet printer, and that means working with a resolution of about 4800 by 6000. That's a 28MB file! For that reason, I think your pixel resolution is a little more important than the small difference in quality between a TIFF and a JPEG at the highest quality level--but you'll have to decide for yourself which factors to favor. If you have unlimited storage space, you can splurge and save high-resolution TIFF images.

Hot Pic of the Week

Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality, and technique. Every month, the best of the weekly winners gets a prize valued at between $15 and $50.

Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 640 by 480 pixels. Entries at higher resolutions will be immediately disqualified. If necessary, use an image editing program to reduce the file size of your image before e-mailing it to us. Include the title of your photo along with a short description and how you photographed it. Don't forget to send your name, e-mail address, and postal address. Before entering, please read the full description of the contest rules and regulations.

This Week's Hot Pic: "Sundown Surfer," by Bobby Deal, Niguel, California

Bobby says that he took this picture one evening last winter, just before dark. "It was quite dark under the pier, and the image was shot hand held with flash," Bobby says. He took this picture in San Clemente State Park.