Digital Focus: Digital Zoom's Ugly Little Secret

Feature: Digital Zoom's Ugly Little Secret

After the number of megapixels, zoom is without a doubt the spec that defines the power of a digital camera. People compare zoom ratings like some guys chat about cars. Conversations typically go something like this:

"What's the zoom on that baby?"

"3X optical, 2X digital."

"Not bad, but I've got a 4X optical, 3X digital under the hood of this little guy. I can shoot the wing of a butterfly at 400 yards."


Digital Isn't Always Better

But even though the digital zoom rating is a common benchmark that buyers use for choosing a camera, it may not deliver the results you expect.

As you probably know, virtually all digital cameras have both an optical and a digital zoom. The camera's optical zoom increases the magnification of a scene by changing the relationship of optical elements in the lens. It zooms in or out while maintaining a sharp, high-quality image at the camera's full pixel resolution. But digital zooms work on a completely different principle.

A digital zoom enlarges the image simply by "cropping" it. As you zoom in on a scene, the camera draws a crop box around the pixels in the image sensor and discards information outside the frame. Only the pixels inside the frame are recorded. And that means that the sensor's full resolution isn't being used. The more you zoom in, the fewer pixels you'll have in your final image. That's a real waste of your camera, because you're throwing away image quality.

With all that in mind, there's no reason to let a digital zoom rating play into your buying decision.

Bottom Line: Avoid Using the Digital Zoom

I give simple advice to everyone who has a digital camera: Never use the digital zoom feature. Ever. Why bother? You can crop the scene just as well in an image editor on your PC. In fact, if it's possible, disable the digital zoom entirely. That way it can't be kicked in by accident and spoil a shot. Most cameras allow you to turn off the digital zoom somewhere in the camera's menu system. Look for a setting in the menu called Digital Zoom, and set it to No or Off.

What if you can't disable the digital zoom? How can you tell when the optical zoom ends and the digital zoom kicks in? In most cameras, the viewfinder displays a gauge while you're zooming so you can tell where you are within the camera's zoom range. Often, there's a subtle detent in the gauge that indicates the transition from optical zoom to digital. As you press the zoom button, the zoom will pause momentarily at the end of the optical range--at the detent in the gauge--before resuming the zoom into digital. When you see the zoom status bar reach the digital detent, take your finger off the zoom button. Consider the digital zoom range off limits.

Do-It-Yourself Digital Zoom

As I mentioned, remember that you can "zoom in" on your pictures after they're on your PC--just use your image editor's Crop tool to hone in on the part of the image that most interests you. Here's where high-megapixel cameras really pay for themselves. If you have a 3-megapixel model, for instance, you can't afford to crop it very much if you want to make an 8-by-10-inch print. But a 6- or 8- megapixel camera has pixels to spare. You can crop away half the picture and still have plenty of resolution to make a sharp, snappy print.

And while no software can ever add information to a picture that wasn't there to begin with, there are some programs that can help you get good-quality prints from lower-resolution images.

For example, you might want to try Pxl SmartScale from Extensis. Pxl SmartScale is a powerful image scaling program that can preserve quality when you make large prints from images that might not ordinarily have enough pixels to print well. I use it frequently, and I find it does an impressive job of retaining overall sharpness when I need to crop a picture to "zoom in" for a better composition. I've found the program for less than $200 at the PC World Product Finder.

Dave's Favorites: Protect Your Pictures With IWatermark

How paranoid are you? Some people don't mind lending money to that second cousin from out of town who is only seen at family gatherings in the company of a parole officer. I'm not quite that easygoing; I get nervous when someone at the next table in a restaurant asks to borrow my bottle of ketchup. What then of my digital pictures, which can end up anywhere on the Internet after I've posted them to a Web site or sent them to a friend?

How can you protect your pictures? Script Software has an inexpensive ($20) and simple solution: IWatermark.

IWatermark isn't an industrial-strength watermarking program; it probably won't protect you from a determined and clever thief. But the program is good enough for routine security, which should satisfy most folks who don't depend on digital photography for their livelihood.

It's a breeze to use. Just drag a single picture or a folder full of pictures to the IWatermark screen to tell it what images to watermark, then specify the watermark text, like "© 2004 Dave Johnson." Here's where the program really gets good: You can specify a watermark image instead of text. That means you can put a small picture of yourself in the corner of the image if you like. Then set a watermark location--such as a corner or the center of the frame--and let it rip.

I say that IWatermark isn't going to stop a determined thief because unlike some comparable programs, this one doesn't hide any identifying data in the substrata of the image. It's all right on top, where you can see it, erase it with a clone brush, or even crop it away. You can minimize the risk by making the watermark large or even repeating it throughout the image--but those tactics obliterate the aesthetics of your picture.

The good news is that IWatermark painlessly lets you inscribe your pictures with identifying data, and it has enough options to make almost anyone happy with the results. It also features a few other cool tools, like the ability to resize images and create small thumbnail images, all at the same time that it prints the watermark.

Q&A: Protecting Your Digital Pictures

I have almost a thousand rolls of slides that I've inherited from my father. Many of the pictures are family shots that the grandchildren would like to see of their parents. Which is better--to save them as a slide show, or just save them in JPEG format?

--Mae Watson, Hamilton, Ontario

When it comes to pictures that have some real value as heirlooms or historical keepsakes, Mae, I wouldn't entrust them to some program's slide show format, which is certain to be both low resolution (probably optimized for the computer screen rather than quality prints) and proprietary. By proprietary, I mean that if you ever stop using whatever program created the slide show for you in the first place, you might lose your ability to see the pictures as well.

Instead, you should use an established format like JPEG (with a high quality/low compression setting) or TIFF. Either of these formats will be around for many, many years to come and should be readable on any computer you're using ten or twenty years from now. And if you save those images at a high resolution, they can be printed and shared with anyone who wants to see small details in the pictures, which would be lost of you used a format that was optimized for the computer screen.

That said, there's nothing wrong with sharing slide shows of these pictures with friends and family--as long as you are careful to save the original pictures as JPEGs or TIFFs as well. Good luck scanning all those pictures!

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: "The Birds," by Jim Michaels, New Berlin, Wisconsin

Usually, when you encounter an assembly of fowl like this, it's digitally manipulated. Jim claims that's not the case in this photo: "I took 'The Birds' on Perdido Key Beach (about 20 Miles west of Pensacola, Florida) using a Canon A40. We were on vacation and my wife attracted all of these birds by feeding them burnt toast."

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