One of the first things that new digital camera owners love to do is send a batch of images to family members or friends. As you may have already discovered yourself, the warmth of reception is inversely proportional to the size of the images that land in your recipients' inboxes.
All too often, budding photographers send full-sized 2-, 4-, or even 6-megapixel pictures as email attachments. Unfortunately, these files take forever to download on all but the fastest Internet connections and are too large to view comfortably on a computer monitor.
Indeed, you should shoot at your camera's highest resolution, but remember not to send those full-sized images to others. All parties concerned will be much happier if you create much smaller "email versions" of your pictures and send those along. This technique is called sampling down. Here'show it works:

1. Use your image editor to resize a copy of the image for easier handling. To do so, use the "Save As…" command in your image editor. The largest size you should send as an email attachment is 800 x 600 pixels, and 640 x 480 pixels will usually do the job.
2. If you're lucky enough to have Photoshop (or Photo shop Elements) as your image editor, use the Image Size function to resize the picture. (Other image editors have similar functions.) When you first open the Image Size dialog box, you'll see the current width and height of the picture. In the settings, those dimensions are 2272 pixels wide by 1704 pixels tall. This shot was taken at full resolution with a 4-megapixel camera. If you sent this picture as-is, the file size would be well over 1 MB even after compression, and a full 11 MB when opened. That's not the kind of attachment you want to send to friends and family.
3. Use this dialog box to reduce the width and height settings to 640 x 480 pixels (or thereabouts). In the above example, these changes shrank the compressed file size to under 300 KB—just a fraction of the size of the original image!
4. Make sure you have both the "Constrain Proportions" and "Resample Image" boxes checked when preparing image copies for email. With the "Constrain Proportions" box checked, Photoshop will automatically change the height dimension for you when you change the width. Photoshop users can also take advantage of the Bicubic Sharper algorithm, which you can select from the drop-down list next to "Resample Image." Since sampling down sometimes "softens" your pictures slightly, many photographers feel the need to sharpen the images after resampling. You won't need to use that two-step process if you select Bicubic Sharper—Photoshop will resample and sharpen for you in one step

"Resampling" is probably one of those words you've heard before but don't quite understand the meaning of. In simplest terms, resampling means that the image editor is either adding pixels to the image or subtracting pixels from the image. Usually you'll want to avoid "sampling up" (that is, adding pixels), because that degrades image quality. But "sampling down," or subtracting pixels, is a great way to reduce the file sizes of image copies that you want to send via email or post on the Web. In other words, when you change the width and height dimensions to smaller numbers, such as 320 x 240, you're sampling down, and both the picture and the file size will be smaller.
If you have a choice, the best image format to use for email attachments is JPEG (.jpg). When you save in this format, your computer will usually ask you which level of compression you want to use. Generally speaking, medium or high gives you the quality you need.
Remember to keep your original image safe and sound so you can use it later for printing and large display. To help eliminate confusion when dealing with these different sizes, you might want to save two copies, calling the original something like vacation one hires.jpg and the more compact version vacation one lores.jpg ("hires" being short for high resolution and "lores" denoting lower resolution).
If you send friends and family smaller, more manageable pictures, you'll hear more about how beautiful your shots are and less about how long the darn things took to download.