The digital age has made it possible for us to share photographs in many new ways. But it has also created new problems.

At "Trailblazer", we love to get your photos. And we really regret having to turn photos down because they won't appear well in print.

The biggest problem for "Trailblazer" today is this: A photo that looks good on a computer screen does not necessarily look good on the printed page. The reason: They use different methods to fool the eye.

Fooling the eye

All picture media depend on fooling the eye. For instance, we see "moving pictures" when still pictures are projected on a screen at 24 pictures per second, each new picture showing things in slightly different positions.

Television shows us 30 pictures per second. It also fools the eye in another way: The pictures are made up of 483 horizontal lines, which you can see if you're close enough to the screen. The bigger the screen, the wider the lines. Photos taken of TV screens usually look terrible on the printed page.

The printed page uses a pattern of dots to fool the eye. The rows of dots are very close together, up to 150 rows per inch or more. The sizes of the dots determine how "dark" an area of the photo looks in black-and-white. Dots of three special colors are combined with black dots to fool the eye into seeing a color photo.

Computer screens use a series of dots, or "pixels". ("Pixel" is short for "picture element".) Unlike the dots on a printed page, pixels are all the same size. Each pixel varies in color and intensity.

There are more rows of pixels on a computer screen than there are lines on a television screen. But a photo of a computer screen still may not look good on the printed page.

Computer screens can have quite a few numbers of pixels per inch, depending on how the monitor is constructed. About 72 pixels per inch is a common standard. Web page designers sometimes work at a total size as small as 640 pixels wide by 480 pixels high - about the best traditional television can do - and it usually looks good on the computer screen.

Digital photos and scans are made up of pixels. Computers can convert these pixels into the dots needed to show a picture in print. And experience has shown that it the digital photo should have at least 300 pixels per inch at the size the photo will be printed to make the photo look good on the printed page. A photo that is 640 pixels wide by 480 pixels high would look its best at only about 2.13 inches wide by 1.6 inches high on the printed page.

This means that a picture downloaded to a web site, or emailed to your family and friends, may not look good in print.

Guidelines for photos

Here are some guidelines for submitting photos to "Trailblazer":

Digital cameras

• The digital camera should have a resolution of at least two mega-pixels. The more mega-pixels, the better.

• Avoid using digital zoom. It reduces the number of pixels in the picture.

• Save the photo at the highest quality available. This will take more room in the camera's memory - but will help make the picture look its best in print.

Traditional photos

• It's best to submit the original photo to us; that way we can have it scanned to match our requirements. We'll return it to you.

• Second-best is a high-quality copy made by photographing the original print on film. Copies made on copy machines usually lose a lot of quality. (Copies made on do-it-yourself photo machines often seen in drug stores may work, depending on the quality of the photo produced by the machine.)

• We can also use a high-quality, high-resolution electronic scan of the original photo, following the suggestions below.

Scans

• If you're scanning a photo or having it scanned at a store, make sure the resolution is at least 600 pixels per inch if the photo is smaller than 4 by 5 inches, and make sure the resolution is at least 300 pixels per inch if it's larger than that. For very small snapshots, 1,200 pixels per inch is better.

• Do not use software to "adjust" the photo. We need the original file to adjust it for the best appearance in print.

• Scan only original, traditional photos. Scans of photos from publications, such as old issues of "Trailblazer", usually lose a lot of quality because of conflicts between the dots in the printed picture and the way pixels are produced.

Submitting digital photos

• Save the photo file in "tif" format if possible. If not, save it in the highest quality "jpg" format you can.

• Never use software to artificially increase the number of pixels in a photo. This just increases the size of the photo file without adding detail.

• Convert scans from color to grayscale; this reduces the size of the file.

• If the size of the photo file is larger than one megabyte, have it "burned" to a CD instead of trying to send it by e-mail. Send the CD to "Trailblazer" in a package designed to protect it from harm. We'll return it to you.

Other factors

Other factors enter into the acceptability of a picture for "Trailblazer". If a photo is blurred, too dark, too light, or has other technical flaws, we may not be able to make it look good enough to print. Prints produced on home or office-type inkjet printers usually cause problems. An 8-by-10 print produced on a six-color (or more) photo printer, however, may work fine.

And remember: We like to share your photos with the rest of our readers. We just want them to look their best in "Trailblazer"!