Beginner Scrapbooking: From Camera to Layout

Pixels and Resolution

In What Is A Digital Image?, I described how a picture was stored digitally in the camera's flash memory card, how to copy the image into your computer, and how to make working copies and backups.

Now let's discuss what happens when you begin editing the working copy of the digital image.

When opening a digital photograph on your computer, the displayed image appears in one of two ways. Sometimes the image will appear larger than your monitor can display. But most often the entire image is viewable because the software "scales down" or displays a smaller version automatically. The original image file still has not changed in any way.

Here is where it becomes confusing for anyone just beginning to do digital scrapbooking. Is my image too large? Is it too small? What should I do next?

Remember that pixel dimension (width x height) is stored as part of the digital image file. However, "pixel" not only refers to a point of light inside your stored digital photo. The same word is used to describe a point of light on your computer monitor. Many people are easily confused because the word pixel actually refers to two different technologies.

A monitor pixel is really made up of three subpixels in the colors red, green and blue. The number of pixels in your monitor depends upon your monitor hardware and your monitor resolution setting. Early computer monitors were limited to displaying at a single resolution only. Today monitors are capable of displaying multiple resolutions starting on the low end at 600x480 pixels and going up way past 1900x1200 pixels. If you don't know at what resolution your monitor is set, ask the nearest computer nerd in your household.

If your original picture was stored digitally with a dimension of 1900x1200 pixels, what happens to your picture when your monitor resolution is set to 800x600?

Nothing!

Image software will typically display either the whole image scaled down to fit the screen or will use a one to one mapping of image pixels to display pixels. When changing to a higher monitor resolution, pictures will appear smaller but the image file remains unchanged. A lower monitor resolution makes pictures look larger. Most people never change their monitor resolution once set to their own preference but may notice this effect when viewing the same image on another monitor with a different resolution.

The point is, the resolution of your computer monitor has absolutely no relation to the final size of the printed digital image.

Just as pixel is defined by two different technologies, so too is resolution.

As defined above, resolution refers to the number of horizontal and vertical pixels in a computer monitor. But resolution is also the degree of sharpness of a computer-generated image as measured by the number of dots per linear inch in a hard-copy printout. This is referred to as DPI or Dots Per Inch. Good quality output on any print device requires the DPI be set to 300.

The important thing to remember here is resolution. Why? Because that's how computer software labels this setting.

Look at the following two screen shots from Photoshop and Paint Shop Pro that were captured right after opening a photo image file from my digital camera.

In the Photoshop image (left) the pixels/inch setting is inside the grey outlined box labeled Document Size and in Paint Shop Pro, it is inside the box labeled Print Size. Both programs use the same labels referring to the image settings: Width, Height, and Resolution. When the resolution is changed here and saved with the modified image file, this information is communicated to the hard-copy printer.

Note that both Photoshop and Paint Shop Pro says my image resolution is 72 pixels/inch far below the print standard of 300. The resolution defaults to 72 because of standards that were set in the early days of computer monitors and are still followed today.

If you take your flash memory card directly to the local photo processing center without editing any of the photo image files, the photo centers know how to adjust for the discrepancy between 72 and 300 to give you the final printed product. All you have to do is select the size of your photo prints and they take care of all the rest.

However as a digital scrapbooker, you are now editing your photo digitally before printing and if you don't pay attention, the final printed image will turn out wrong.

See what happens to the Document Size when the resolution is changed.

Notice that the pixel dimensions remain unchanged while the document size adjusts to the change in resolution. Also, the Resample Image box is unchecked. Image resampling is discussed in-depth in another article.

Avoid any print errors by making sure your digital layout with any photo images therein has a resolution set to 300.

One last thing. Did you notice that my image file pixel dimensions are 3264x2448. I have an 8 megapixel camera set to take pictures at a high pixel count. Many people refer to this setting as the resolution of the camera. The word "resolution" used in this way refers to the quality of the camera, as in the greater the resolution, the better the picture.

Is it any wonder why you were confused?

So let's wrap this up by reviewing each of the definitions explained above for pixel and resolution.

pixel

1. Short for picture element.
2. A single point of light stored in a photographic digital image file.
3. A point of light on your computer monitor made up of three subpixels: red, green and blue.

resolution

1. The number of pixels across and down on a video display screen or computer monitor.
2. The degree of sharpness of a computer-generated image as measured by the number of dots per linear inch (DPI) in a hard-copy printout.
3. The amount of pixel dimensions at which a digital camera can capture an image; the greater the resolution, the higher the pixel dimensions, the more data captured per picture.
   

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