People sometimes ask how many digital photos can be stored on a CD or DVD. That fact of the matter is that it is very difficult to say with precision the number of images.

Image file sizes vary according to the type (JPEG, RAW, TIFF, Video), resolution and the compression level you set in your digital camera. The size of a digital camera, even shot at the same resolution, can vary due to the colors in a scene.

The number and degree of the brightness of colors in a scene can influence file size. Additionally, if you shoot a subject in black and white, the file size will be a smaller than if it been had shot in full color.

Editing and resaving an image can also significantly increase or decrease the size compared to the original file.

The average size of a five megapixel color image file is between 2-2 1/2 megabytes when shot at JPEG fine (least compression). That means you can get about 280-300 onto a CD that has a 700 megabyte capacity.

The most important thing is not how many digital images can be stored on a CD or DVD, but that you back up originals of your photos.

Increasing numbers of photographers store digital photos with online photo hosting or storage services.  Most services offer one to five gigabytes of free store. Additional storage can be purchased for a modest annual fee.

There are other online services, such as Carbonite, which offers unlimited online backup for all types of files, including image files, for a modest annual fee.