Digital Upsampling & Interpolation

What are digital upsampling and interpolation?

According to dspGuru: “ Upsampling is the process of inserting zero-valued samples between original samples to increase the sampling rate. (This is called “zero-stuffing”.) Upsampling adds to the original signal undesired spectral images which are centered on multiples of the original sampling rate. “Interpolation”, in the DSP sense, is the process of upsampling followed by filtering. (The filtering removes the undesired spectral images.) As a linear process, the DSP sense of interpolation is somewhat different from the “math” sense of interpolation, but the result is conceptually similar: to create “in-between” samples from the original samples. The result is as if you had just originally sampled your signal at the higher rate.” (dspguru).

When does it occur?
It occurs at some point in almost every digital photo. Interpolation occurs, “anytime you resize or remap (distort) your image from one pixel grid to another. Image resizing is necessary when you need to increase or decrease the total number of pixels, whereas remapping can occur under a wider variety of scenarios: correcting for lens distortion, changing perspective, and rotating an image” (Cambridge).

When people edit a photo to enlarge a picture the following artifacts can occur:
Aliasing, Blurring, and Edge Halo artifact examples can be found on the lightning bolt photos on the following page…/image-interpolation.htm.



Notes on Digital vs Optical Zooms:
Most digital cameras come with both an optical zoom and a digital zoom. Cellular phone cameras come with just a digital zoom. Optical zooms use principles of light and optics to magnify the light prior to reaching the sensor on the camera. Digital zooms simply, “degrades quality by simply interpolating the image — after it has been acquired at the sensor“ (Cambridge)


Works Cited
DIGITAL IMAGE INTERPOLATION. (n.d.). Retrieved May 10, 2015, from…/image-interpolation.htm

Interpolation. (n.d.). Retrieved May 10, 2015, from

Samuel Sanfratello

Samuel Sanfratello

My name is Samuel Sanfratello (Sam). I am a NY state dual-certified Mathematics and Special Education teacher and a nationally certified Consulting Hypnotist. I am also the proud owner and operator of two companies: Monroe Hypnosis and Rochester Analytics. I am a 2nd generation Spiritualist (American Spiritualism) and a certified Medium with the Plymouth Spiritualist Church (the mother church of modern spiritualism). I am an organizer of the Rochester Paranormal Researchers, founded in 2007 and a lead investigator for the Paranormal Science Institute’s F.R.I.N.G.E team. In my spare time, I give back to my community by doing volunteer work for my church and for my local chamber of commerce. I became interested in the paranormal when I spoke with a spirit in my grandmother’s house in the early 1980s. I enjoy reading publications and scientific articles about the fringe sciences and I enjoy sharing these understandings with others.
Samuel Sanfratello

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