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Have your friends ever emailed you photos that exceed the boundaries of your computer monitor? Or worse, have your friends complained about the size of photos that you've sent? Either way, the problem is caused by an overabundance of pixels. In addition to producing pictures that don't fit on-screen, having too many pixels creates another problem for Internet photo-sharing. Every pixel adds to the picture file size, which increases the time that it takes for your photos to make their way through the Internet pipeline.
Your camera's resolution setting determines how many pixels a photo contains. Even if you shoot a picture using your camera's lowest resolution setting, you probably will need to dump some pixels from your photo to shrink it to an appropriate size.
How many pixels are enough?
To figure out how many pixels your email or Web picture needs, you first need to understand how a computer monitor displays what you see on-screen.
Like your digital camera, a monitor displays text and images using pixels. And just as you can select from different resolution settings on your camera, you can choose from a variety of monitor resolution settings, each of which results in a specific number of screen pixels. For example, you can choose from screen resolution settings such as 640 x 480 pixels, 800 x 600 pixels, 1024 x 768 pixels, and 1280 x 1024 pixels.
 | When you display a digital photo, the monitor uses one screen pixel to reproduce one photo pixel. This one-to-one relationship between screen and picture pixels means that if the pixel dimensions of your picture — pixels wide by pixels tall — match the screen resolution, your photo fills the screen. |
To set the screen display size, you simply decide how much screen-pixel territory you want your photo to consume and then change the image pixel count to match. Keep in mind, though, that people who view your pictures have control over the screen resolution setting on their monitors, and so ultimately have control over the display size of your images.
Given that you can't predict the monitor resolution that will be in use when your pictures are viewed, follow this advice:
- Size your pictures with the lowest common denominator in mind. Keep the image small enough that someone viewing the photo at a screen resolution of 640 x 480 can see the whole picture without scrolling the display.
- Remember that the Web browser and email window themselves eat up some of the available screen space.
- For pictures that you plan to attach to an email message, limit the picture height to 300 pixels and the picture width to 400 pixels. This allows enough room for the picture to display in the message window even on a monitor set to a resolution of 640 x 480.
- For Web pages, the same pixel dimensions work fine as long as your page has only one image. If you have multiple photos on a page, you should keep your pictures even smaller. Each photo you put on the page adds to the page download time, and you don't want visitors to your site to have to wait several minutes to display the page.
 | These guidelines assume that you're preparing your picture for on-screen viewing only. If you want people to be able to print a good copy of a picture, you need to provide them with a much higher pixel count. |
Trimming the pixel count
Your photo-editing software should offer a command that enables you to check the pixel count of your photo and eliminate any excess pixels. The following steps show you how to get the job done in Photoshop Elements, but the basic concepts apply no matter what software you're using:
1. With your picture open, choose Image --> Resize --> Image Size.
The Image Size dialog box appears.
2. Select the Resample Image check box.
When the box is selected, the Width and Height options in the Pixel Dimensions area at the top of the dialog box become available.
3. Select Bicubic from the drop-down list next to the Resample Image check box.
4. Select the Constrain Proportions check box.
5. Enter the desired horizontal pixel count in the Width box at the top of the dialog box.
Or enter the vertical pixel count in the Height box, again using the box in the Pixel Dimensions area at the top of the dialog box. When you change one value, the program automatically adjusts the other value to keep the original image proportions intact.
6. Click OK to close the dialog box.
7. Choose View --> Actual Pixels to see the image displayed at its new size.
Remember that the picture will display at a different size when viewed on a monitor that doesn't use the same screen resolution that you're currently using.
If you don't like the new size, choose Edit --> Undo and try again.
8. Save your resized picture file.
If you want to make additional changes to the picture, choose File --> Save As and save the photo in a non-destructive file format, such as PSD or TIFF.
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