Replacing traditional (analog) photo frames that have a single photo in them with a digital photo frame, allows you to show off an entire vacation or series of family shots in the same space. When they first came out, they were expensive, low-resolution and limited to how many photos they could display. Today, they are cost-effective, high-resolution and have a myriad of storage options for large quantities of pictures.

The basic items that you should start with are the size and resolution of the display, the amount of internal memory and the card slot options for transferring or displaying the images.

As with most digital displays, digital photo frames are measured diagonally which means that a 1 inch difference (7” vs 8” for instance) translates to a significant improvement in overall picture size. If you plan on displaying the frame in an area where it will be viewed from far away, be sure to get the largest display your budget will allow with a resolution of 640 x 480 or higher (most of today’s frames tend to be in the 7” to 10” range).

The next item to evaluate is the amount of internal memory the frame has built-in. The higher this number is, the more pictures you can display without having to purchase a dedicated memory card.

Some of the manufacturers will make claims about the number of pictures the frame can hold, but they tend to use lower-resolution images in their calculations so don’t rely on that specification (resolution determines how much space each picture will take - the higher the resolution the more space each photo will require).

To calculate how many pictures the internal memory will hold, take a look at the average size of the pictures taken by your digital camera and divide the stated memory by that number. For instance, if your pictures each take 2Mb of space on your computer’s hard drive and the unit you are considering has 128Mb of internal storage, you will be able to transfer 64 images directly into the frame.

If you can’t find any mention of internal memory, it generally means that you will need to purchase a memory card in addition to the frame in order to display any pictures, so be sure to calculate that into the final price (this is very common in lower priced frames.)

The third basic item is the number and types of memory card slots that the frame will accommodate. The best frames support all of the most popular formats: Secure Digital (SD), Compact Flash (CF), Multimedia Card (MMC), Sony’s Memory Stick (MS) and in some cases Extreme Digital Picture Card (xD).

Even though your camera uses one specific type of memory, having many options will come in handy for friends digital cameras that use a different kind of memory card or if you have more than one type of digital camera yourself. It also gives you the flexibility to buy the cheapest format memory card if you buy one dedicated for use in the frame.

Once you have narrowed down the choices based on the first three criteria, things like interchangeable frames, the ability to watch and listen to video files and portability (some smaller units will run on batteries so you can take it with you) might be items for consideration.

And finally, remember that you will need to plug it into an electrical outlet, so make sure there is one in the area that you plan to display the picture frame.