How A Digital Camera Works?

Posted on Jul 19 2013 - 1:15pm by Chris Pentago

Today’s digital cameras are all surrounded by a common misconception: the fact that these cameras make no use of film and they store data as files, many of us think that they must use a very different technology for capturing images.

Canon Ixus

Photo Credit: Flickr/paldies

However, if you didn’t know, the old camera you may still have somewhere around the house and the very expensive camera you may have gotten for your birthday are similar in many respects.

For example, the light camera features a shutter which will open for a fraction of a second in order to admit light into the body though a minimum of 1 lens. If needed, you can also adjust the lens to bring objects at different distances into focus, but you may also tack on different lenses.

However, the main difference in the way these 2 types of cameras work lies in the way they record incoming light:


Photo Credit: Flickr/Dboybaker

A film camera has a shutter that opens for a set amount of time (usually a fraction of a second), admitting light into the body of the camera through at least one lens. Obviously, that lens can be adjusted to bring other objects at other distances into focus, or different lenses can be tacked on.

1. Digital cameras for instance, make use of an array or grid of photo sensors in order to record the incoming light pattern. When struck by the incoming light, each sensor will return an electrical current.

3 Megapixel

Photo Credit: Wikimedia/johncarney

2. Film cameras on the other hand, make use of a strip of light sensitive celluloid that’s coated with silver halide that retains the image. Thus, the film will eventually need to be developed and the positives and negatives obtained can be used to make further copies of the photo.

Due to the fact that the amount of light influences the amount of current that is returned, the electronic innards of the specific camera model you’re using can easily combine the different current levels into a composite data pattern which represents the incoming light.

When using digital cameras, you’ll find they use underlying technologies like a program and a light sensor, with the latter most of the times being a CCD, while the program is the firmware that’s embedded into the camera’s circuit board. This is much like the programs that make your iPod or your microwave oven work.



Photo Credit: Flickr/xJason.Rogersx

First of all, I want to focus on the CCD because I think it’s very important for understanding the way digital cameras work. In this regard, you should know that there’s also another type of light sensor which can be used and that is called the CMOS type. Even though the principles are the same, the mechanics of how they do what are different.

So, getting back to the CCD, just think of it as being a grid that contains millions of small squares resembling a solar cell. We all know that solar cells deal with converting electrical energy, so when there’s more light, there is also more electricity produced and vice-versa. As a result, I hope you can realize where we’re going with this CCD thing.

Thus, each condition of the light (like intensity and brightness) will generate a certain electrical charge and the charges produced will go through a grid of electronics where the firmware will interpret them. The firmware is aware of the meaning of each and every small charge and thus it manages to translate it into info that includes the many qualities of the light (like color) picked up by the CCD.

Note that often photos require additional color tuning in order too look either more natural or vibrant. There is multitude of photo retouching software’s for this purpose but that’s the topic out of scope of this article.

Color Settings

Photo Credit: Prolab Film Processing

Spatial Sampling

When it is output, the photosites in the camera’s sensors will correspond 1 to 1 with the pixels in the digital image. Mostly we’re familiar with photosites by calling them pixels, which are arranged in a rectangular grid. To offer you an example in this regard, if you have a Canon 20D digital camera, then you should know that the array is 3504 by 2236 pixels which in total equals to 8,2 million pixels.

Dead Pixel

Photo Credit: Flickr/Marcelo Alves

If you want, you can imagine this grid as a chess board, where the size of each square is really small. However, when these squares are viewed from a distance, they will trick the brain and the eye into thinking that what you’re looking at is a continuous tone image. If you want, you can try enlarging any pictures you have and you’ll notice that they’ll become pixelated.

Focus and Exposure

There are 4 types of lenses that digital cameras have and they will be included below.

Replaceable lens systems: These share many similarities with the replaceable lenses on a thirty five millimeters camera. There are some digital cameras out there that use 35 millimeter lenses.

Digital zoom: In this case, the camera will basically take pixels from the image’s center sensor and then using interpolation, it will make a full sized image. Based on the sensor and the image’s resolution, this approach can create fuzzy or grainy images. If you want, you can do the same thing manually by making use of image processing software. Just take a picture, cut the center out and then magnify it.

Optical-zoom lenses (auto-focus): Sharing many similarities with the lenses you can find on a video camcorder, these feature, automatic focus, but also telephoto and wide options. However, depending on the camera used, it may not or may support regular focus. These will basically change the lens’ focal length rather than just magnify the info hitting the sensor.

Fixed-focus, fixed-zoom lenses: These types of lenses that you can find on the inexpensive film cameras and the great news about these lenses is that they are also disposable. Even though they are fairly limited, they are quite great for taking snapshots.

Understanding the way a camera works will allow you to better understand what you’re looking for when deciding to get one, based on the type of photographs you want to take, their quality and also resolution.

Different cameras come with different specifications that may initially sound very appealing and also confusing, but being aware of how a camera works, you’ll be able to know exactly the model that will perfectly fit your needs.

About the Author

Chris is experienced web developer/designer and computer geek interested in key technologies to make your online business perform. During his career he worked for some of the biggest Australian brands. Currently experimenting with all sorts of Unix-like operating systems and Ninefold virtual machines.