Today’s camera brochures and specs lead us to think that the number of megapixels
makes all the difference in the world; like a raucous party - the more the
better. But this isn’t entirely true –
in either case.
The number of megapixels does make a difference, but only up
to a point. We need to consider the size of the image sensor. Remember, pixels
are photo-receptors etched into the silicon of the image processors. The job of
the pixel is to record the photons (light) reflected through the lens.
We can compare it to a jigsaw puzzle, with each pixel holding
a piece or an element of the picture.
A digital image is made up of numbers, millions of 1’s and
0’s that determine the colors of the composite pixels, their placement, and
light intensity. When digitally
processed, each pixel’s signal is interpreted as to color and light intensity
and, collectively, processed back into a recognizable image of the captured scene.
Pixel Over-crowding
More pixels may mean
more information but they don’t necessarily mean a clearer image or higher
resolution. If you increase the size or the
amount of pixels without increasing the size of the sensor the pixels are going
to be crowded together and pixel overcrowding leads to digital noise. When
pixels are in too close proximity, in some cases, the digital signals of the
photons can interfere with each other, resulting
in noise. In other instances, some of
the light can spill off the sides of the pixels leading to image degradation.
Digital Noise
We are not aware of them per
se, but electronic signals are being transmitted around us non-stop. If
your television is on, broadcast data is
being transmitted over cable or through an antenna. Switch on your car radio
and an audio signal the transmitter’s station en route to the cars receiver via the antenna.
For digital cameras, the signal is the light that travels through the lens and
hits the camera sensor.
No matter what type, some degree of noise is always present
in these transmission. In terms of TV when an antenna, rabbit ears or roof, was the receiver, we experienced noise in the
guise of a “snowy” picture or visual
static. Noise in radio transmission produces a crackling sound often painful to
the ear.
When it comes to the digital camera, noise can affect a video frame in a variety of
ways.
It can result in a
frame of randomly spaced brightly colored pixels:
It can obscure small features and
skew the color
It can result in a lack of clarity
in darker areas
One way to combat digital noise in today’s megapixel world
is to use larger image sensors while at the same time, improving image quality.
Larger sensors are a win-win solution:
·
Larger sensors not only hold more pixels they can hold bigger pixels.
·
Bigger pixels hold more light.
·
The more light, the stronger the digital signal.
·
The stronger the digital signal, the greater the
chance of overcoming the digital noise.
In addition, photosites themselves can be spaced farther
apart on a larger sensor, creating less electrical contamination resulting in a
stronger signal and less noise from the start; a higher signal to noise ratio.
Signal to Noise Ratio
The term signal to noise ratio is one we come across in
electronics, and it’s a good thing. It’s relatively easy to comprehend, A
higher signal to noise ratio means the signal overwhelms the noise, resulting in clearer transmission of whatever type of
signal is involved. In the case of video, relatively little digital noise translates
into better clarity and more detail.
To sum it up, the larger the sensor you have in your camera, the less
noise, greater detail, and more superior the image quality you will obtain. But human
nature being human nature, although you'll have so much more than you did just
a few years earlier, you'll still want more.
Next post – larger
sensors, more dynamic range
