The great thing about writing this column over the last five years is that I get to hear from you on a regular basis.

Many readers send me digital photos they've cooked up based on techniques I've described. Others write in with questions or suggestions for topics. When I see the same question a few times, I know it's something that I should address in Digital Focus.

Last month I answered a few reader questions; this week I'll tackle some more.

Online Photo Sharing

What do you recommend for sharing digital photos on the Web?
--Adrienne Carter, North Bend, Washington

That's an easy one, Adrienne. I am a devout disciple of Flickr.

In fact, you can visit my Flickr home page. Stop by, browse my photos, and leave some comments. Everyone is welcome.

What do I like about Flickr? There's a great sense of community. After you upload your photos, you can tag them with descriptive words--and then people around the world can browse your pictures using those tags. It's really neat to click a tag called Puget Sound and see my own photos along with ones from a dozen other photographers. If I like what I see, I can add comments and link to other images from my Flickr site.

Many people use Flickr for free, so be sure to try it out. There's also a subscription version that offers a few extra features.

Naming a Set of Photos

Is there any way to control the file names used by digital cameras? I'd like to take different series of pictures, each with a unique naming convention.
--Beau Poynor, University of Arkansas

The easiest way to do that is to store each series in a different folder on your camera's memory card, Beau.

Many digital cameras let you specify a folder on the camera's memory card into which it'll store the photos. So you can start shooting in Folder A, then switch to Folder B when you begin working on a different series. When you transfer them to the PC, you can easily give each set of photos a unique name since they live in different folders.

What Is a "35mm Equivalent" Lens?

I see this all the time--cameras that refer to the focal length as "35mm equivalent." What is that all about?
--Carl Bennett, Etna, California

The focal length of a lens is essentially a measure of how much it magnifies the scene. A low number generates a wide-angle view, while higher numbers give you more magnified images, or telephoto views. The exact magnifying power of a given focal length depends upon the properties of the lens and the size of the camera's image sensor or film. The sensors found in most digital cameras are smaller than 35mm film, so a lens on a digital camera will create a more magnified image than a similar lens mounted on a film camera.

Since many people know what to expect from various focal lengths in the 35mm film camera world, camera manufacturers usually provide the focal length of a digital camera in 35mm equivalents--it's just more commonly understood, so it's a good "standard" way to talk about lens performance.

Finding an Old Manual

I lost the manual for my Canon Powershot. Is there any way to track it down online?
--Mandy Wright, West Lawn, Pennsylvania

I might have good news for you, Mandy. A Web site called Henry's maintains an expansive collection of user guides, including camera manuals. It's not comprehensive--the only Nikon camera on the list is the new D200, for example, and all of the Canon camera links steer you to Canon's digital camera Web site. But Henry's does provide manuals for many cameras. And if your model isn't listed, a trip to the manufacturer's Web site will probably get you what you're looking for.

How Long Does a Digital Camera Last?

I have had a Canon digital camera for only about a year and recently the lens stopped opening when I turn on the camera. The display says there is an "E18 error." Instead of buying a new camera, I thought I'd get a used one to save some money. What kind of life span should I expect?
--Bridgett Bayer, Australia

I'm sorry to hear about your problem, Bridgett, but your story is thankfully unusual.

Actually, let me correct myself--I've heard reports about the dreaded E18 error, which refers to a mechanical problem with the lens on some Canon digital cameras. Read "Digital Camera Disasters: Will Yours Get Fixed?" for more on the issue. However, this problem affects a very small number of Canon cameras overall. If you buy another Canon camera, odds are that it would work flawlessly.

But you asked how long digital cameras will last. The answer is quite a long time. I have an Olympus digital camera that's about five years old, and it's still going strong. I know people using the same digital camera for three and four years. That's an eternity in digital camera years, since today's cameras offer dramatically better resolution, image quality, speed, and memory capacity than earlier models. It's nice to know that most cameras will continue to last for as long as we need them to, and that we can upgrade when it suits us, not when it suits the camera manufacturers.

There are two ways that digital cameras fail. You can expect that eventually a camera will break mechanically, as with the Canon lens. Also, a camera's LCD and sensor slowly degrade over time: Pixels can and will stop working.

If you're considering a used camera, it's a really good idea to try it before you buy--especially if it's more than a couple of years old.