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 http://www.cambridgeincolour.com/tu…/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)
DIGITAL IMAGE INTERPOLATION. (n.d.). Retrieved May 10, 2015, from http://www.cambridgeincolour.com/tu…/image-interpolation.htm
Interpolation. (n.d.). Retrieved May 10, 2015, from http://www.dspguru.com/dsp/faqs/multirate/interpolation