A (simplified) Look at Camera Sensors

The sensor on your camera is 14 megapixels and 6.17x4.55 mm in size. By comparison, a Nikon D3100 (an entry-level DSLR) has a sensor that is also 14 megapixels, but its physical size is 23.1 x 15.4 mm.

Even more expensive DSLRs, known as "Full frame," have a sensor that is roughly the size of 35mm film (about 36 x 24 mm).

Why this matters:

Sensor size is important because it tells us something about pixel size. Think of each pixel on a sensor as a rain gauge, basically a small cup that catches water. Photons of light striking that pixel are like individual rain drops. When you take a picture, the camera opens the shutter and allows light (rain drops) to land on the sensor, falling on individual pixels (rain gauges). When the exposure is done, the camera closes the shutter and measures the figurative water level of each pixel, and from that information assembles an image.

Now, what would happen if we make the opening on a rain gauge bigger? Well, it would be able to collect water faster because it would collect more rain drops. That means you could leave it outside less time and collect the same amount of water. Or, conversely, you could collect more water in the same amount of time as you could with a smaller rain gauge.

Now back to cameras:

A camera with the same megapixel count (the same number of pixels) but with a larger sensor will collect more light per pixel than a camera with a smaller sensor. When you are dealing with the high shutter speeds that are typical for hand-held photography, the effect of catching or missing individual photons (raindrops) starts to matter. This effect presents itself visibly as "noise" in the image when viewed at 100%, as some nearby pixels catch more more photons than others (due to their random nature).

The larger the pixels, the less the random nature of light effects your image. You have actually observed this effect for yourself when you say that your pictures look good when you zoom out. By zooming out you are in effect blending nearby pixels together, creating fewer but larger pixels.

The reality of the situation:

Most pictures, even those a professional has taken, are never viewed at 100%. Whether they are uploaded to the web or printed on a photo printer, almost all images undergo some amount of resizing, de-noising, and editing before you see them.

As you will often hear repeated on this site, the quality of a photograph ultimately has far more to do with the photographer than the camera, so you shouldn't worry if your images display some noise at 100%. If it really bothers you, there are some things that you can do to try to decrease the noise you see in your images:

• Pay attention to the ISO your camera is using. This is related to how much light is hitting the sensor, and how much the camera has to scale the values it measures from each pixel to get a bright looking image.

• Post-process your images with a noise-reduction filter.