Last week I began my discussion about digital image sensor size, this week I will finish that discussion by talking about how image sensor size affects the quality of images.
As you remember from last week, the size of the image sensor compared to a 35mm or full frame sensor when using the same lens produces a cropped image. But what else is happening on smaller sensors?
Sensor size effects the dynamic range of the camera. Dynamic range is the range of light values from dark to light the camera can record. Smaller sensors have smaller photo diodes, the piece that actually accumulates light and converts it into an electrical signal that the camera will eventually turn into a photo. Because the photo diodes are smaller, they reach their peak recording ability faster, resulting in a camera that has less ability to record all of the different levels of light in a scene. With larger sensors, the photo diodes are larger, which allows them to better capture the light levels resulting in a better quality photograph. If you have ever compared two similiar photographs, one from a digital SLR (with a larger sensor) and one from a digital point and shoot (smaller sensor) you will likely have noticed the digital SLR produced a less contrasty photograph. This is because of it’s increased ability to record more accurately the light in the photograph.
Noise also has a relationship to sensor size. Again, smaller sensor sizes produce noisier images. Noise is the static like pattern you may see in your images, most often in an area of constant colour, such as the sky. Temperature and ISO also affect the amount of noise present in an image. Camera’s with larger sensor’s have better ability to capture an image without capturing a lot of noise. Smaller sensors are more prone to noise.
Another issue arising from smaller sensor is their increased depth of field. With the small sensor used in digital point and shoot cameras, depth of field increases dramatically. With the increase in depth of field comes a decrease in the camera’s ability to isolate your subject.
There are of course advantages to a smaller sensor digital camera. Smaller sensors are lighter, less expensive to manufacture (and therefore to purchase) and require smaller lenses. The advantages of superior image quality in larger sensor far outweigh the advantages of a lighter camera though. With reduced noise, greater dynamic range and better ability to manipulate depth of field, larger digital image sensor sizes are well worth their money.
The digital photography tip of the week is written by the PCIN Assistant Editor, Chris Empey. Chris is a long time photographer and is currently the vice-president of the Niagara Falls Camera Club. You can see more of his photography at his Photo of the Day website.
If you have a tip to send Chris, or a question about digital photography he can address in the newsletter, send it to chris@pcin.net.