FYI-Pixel Interpolation Theory-Pg1 - Cuddeback

Cuddeback ® Technology
Topic: Pixel Interpolation vs Native Image
Making up or adding pixels to increase the megapixel rating of a camera
Pixel interpolation is a means for a camera manufacturer to use smaller megapixel (MP) image
sensor to create larger megapixel images. For example, a camera manufacturer could put a 2MP
sensor into the camera, but specify that the camera is 8MP. We will explain how this technique
works and why Cuddeback does not use pixel interpolation in our cameras.
Step 1: For this discussion, let’s assume we have an imaginary 16 pixel camera in a 4 x 4 pixel
arrangement. Further assume we use this imaginary camera to photograph a 4 x 4 grid of
colored tiles such that each tile equals one pixel. The resulting image is shown below. We call
this the native image.
=
Original image (16 pixel)
Native image (16 pixel)
Step 2: Pixel interpolation techniques are used to increase the pixel count by a factor of 4. In our
simplified example, the 4 x 4 grid is converted to an 8 x 8 grid. This is represented in the image
below. Note: in the following diagrams the “O” represents the original pixels.
O O O O
O O O O
O O O O
O O O O
16 pixel image increased to 64 pixel image.
White area is where pixels need to be added,
or where interpolation occurs.

Cuddeback ® Technology
Topic: Pixel Interpolation vs Native Image - page 2
Making up or adding pixels to increase the megapixel rating of a camera
Step 3: Next, the software calculates what color the added pixels should be. In our example
you would expect to get a final image that looks like this:
Expected “Interpolated” image
But that is not what happens. Instead, the software calculates what it thinks the pixel’s color should
be based upon the color of the adjacent pixels. The result is somewhat like what is shown below. In
this example, green is created because the software averages the blue and yellow pixels. The
resulting image does not look like the original image or the object photographed.
Actual “Interpolated” image
Generally, pixel interpolation results in images with less clarity and color distortion. Of course, in the
real world where images are taken of complex objects, the clarity and image errors would not be as
great as shown here. However, pixel interpolation does artificially create pixels and calculates what
color they should be.
So, why would a camera manufacturer use pixel interpolation We don’t know what their intentions
are, but we suspect the reason is that it allows the manufacturer to use cheaper 1.3MP or 2.0MP
sensors and then use pixel interpolation to create 5MP or 8MP images – tricking the consumer into
thinking they are buying a true 5MP or 8MP camera when, in fact, they are buying a lesser 1.3MP or
2MP camera. If this sound likes cheating to you, that’s because it is. Cuddeback never uses pixel
interpolation and we always specify the native megapixel rating of the sensors. With Cuddeback,
5 megapixels really are 5 megapixels.

Cuddeback ® Technology
Topic: Pixel Interpolation vs Native Image - page 3
Appendix
If pixel interpolation is so bad, why was it invented The real purpose of pixel interpolation is to allow
viewing small pixel count images on computer monitors. For example, the typical computer display
has 1.3 million or more pixels. Many older digital cameras had only 300,000 pixels (VGA resolution).
Thus, the image did not have enough pixels to fill the entire monitor screen. To allow the image to fill
the entire computer screen, pixel interpolation was used to add extra pixels to make the image fit the
computer monitor. Pixel interpolation is also used to when viewing images on a computer and the user
enlarges (zooms in on) a portion of the image such that the pixels must be created to fill the monitor
screen. We don’t think anyone intended this technique to be used to allow cameras to create more pixels.
In fact, we are not aware of any major professional digital SLR camera manufacturers using this technique.
We have only seen this technique in some scouting cameras and very low-end point-and-shoot cameras.
8MP Interpolated Image
5MP Native Image
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