How to Up Sample a Digital Photo Via Interpolation

Upsampling is a method used to take a photo and increase it's resolution without dealing with jagged, obvious pixels. This is done by taking a photo and adding filler pixels in-between the actual pixels, which allows the picture to increase in size without looking too bad.

This method is used for photo's that you want to create a large print from, but cant due to the resolution of the picture. This does create a small loss in quality, with the degradation becoming more obvious the more you increase its size.

If you want to take a photo and increase it's resolution using interpolation, also known as upsampling, then this tutorial is for you. Read on to find out the easiest method to increase the resolution of your photo.

Items Needed:

Digital photo
Computer
PhotoZoom Pro

Step 1: You will need software to increase the photo's size. There are plugins for Adobe Photoshop available that can do this. This tutorial, however, is using PhotoZoom Pro for two reasons: it doesn't require you to invest in Photoshop, and it does a better job than most of the plugins available.

The software is available for a free trial, but you will need to purchase it if you want to continue using it.

Step 2: Start the program and locate a photo that you would like to increase by clicking OPEN in the upper left corner of the program. Once it is loaded, you will be able to see any changes made at full resolution. Focus on a part of the phot that has a lot of texture or different details so you can see the full effects of the interpolation.

Step 3: Choose the type of interpolation you want to use in the bottom left side of the program. S-Spline XL is perfectly fine, but feel free to play around with different options to see which one produces the ideal effect for your preferences.

Finally, you can use one of the presets to create a photo effect. You can, however, get better effects with editing programs, so I would leave that one set to Generic.

Step 4: Now that you're ready to increase the size, simply type a new resolution into the Pixel Size box, and it will increase in size. Note that as the file gets larger, so will the size.

Assuming you want to create a print, you will need to increase the photo to a size larger than your desired size, so that it will look better when reducing in size for the print. So, for example, for a print I made at 20" long, I increased the size of the photo to nearly 40" - this made it look sharp and crisp when printed at 20".
Step 5: Once the photo is at the size you want, you're ready to save it. Do this buy clicking Save at the top of the screen. Choose a save location, and then a box will appear. In this box, choose if you want a compression (reduced file size and quality), and if so, which kind you want.

Choose the level of quality you want, and then choose SAVE. It will take a while depending on your settings, so be patient.