Megapixels

Mega Pixels, How Many is Enough?

When purchasing a digital camera the number of Mega Pixels is an important choice to be made. Understanding Mega Pixels can help you make the right choice.

Mega: 1. one million.

Pixel: 1. The word Pixel was created by combining "picture" and "element" (element in the sense that it is the smallest part from which something is made.) A pixel is a small dot of color that makes up the color on a television or computer screen. Each pixel is only a single color — red, green or blue but Pixels are small enough that the red, green and blue pixels appear to blend together to create a wide range of colors.

Mega Pixel: 1. one million pixels. For instance, a 5 Mega Pixels camera has five million pixels to record the image.

Sensor: 1. The sensor in a digital camera is a device that is made up of rows of pixels, each of which is sensitive to light. When a digital camera takes a photograph the light entering the camera is focused on the sensor, which records the light as red, green and blue light (RGB). Each pixel is able to record a single color of light. These three colors (RGB) when combined make up the colors that we see. RGB is the technology that is used to capture and project color images for television, computer monitors, etc. Film for a camera has three layers (Red, Green and Blue) that record the light. Depending on the quality of the "sensor" in the camera it can capture over 2,000 shades of each color - red, green and blue. The more shades of each color (RGB) that are recorded the more actual colors that are recorded.


Sensor

There are different ways to arrange the pixels but only one in every four pixels captures the color red and only one in every four squares captures the color blue. The green pixels are much less sensative to light than the red and blue pixels so there are twice as many green pixels. Since the camera can not capture a complete picture of any of the colors it uses computer programs to "fill in the blank" areas of color. These programs do a good job but no matter how good they are they can only go so far in replacing the missing color and detail information.

The more pixels there are the more detail that can be captured by the sensor and the smaller the holes of missing information are. Generally a higher mega pixel camera will do a better job of accurately reproducing the subject that you photographed with the result that the camera can more accurately fill in the missing data.


In this illustration the ball is being photographed. The image of the ball is being recorded by the sensor.

The illustration below shows the individual RGB colors as they are captured by the sensor and a final image. The more pixels there are on the sensor the finer the detail is and the smaller the holes of missing data are.

a low mega pixel capture a higher mega pixel capture

The processor in the camera combines all of the colors together. The camera will do it's best to combine the red, green and blue colors together to create a sharp photo that is accurate to the original subject that was photographed. The more pixels there are on the sensor the sharper the image will look.

Additionally there is a thin wall between pixels that keeps the light from one pixel from spilling over into the pixels next to it. The smaller the sensor, and the smaller the individual pixels are, the thinner the walls are and the more likely there is to be spill over, which will cause problems with image quality.


In general a smaller sensor will not produce the quality of image that a larger sensor will, which is in part due to technical issues mentioned here and the lenses ability to maintain a high quality sharp image with a smaller capture area.

When purchasing a camera Mega Pixels is a major factor to consider but there are other factors that affect the final image quality. These includes the components that go into the manufacture of the camera, how well the camera is engineered as well as the quality of software used by the camera internally.


So, how many Mega Pixels is enough?

In a way a camera is a lot like a car. Years ago I owned a VW station wagon that had the same engine in it that was in a Porsche sports car. It had tires, transmission, a steering wheel, etc. Of course that didn't mean that my VW was a Porsche. It didn't drive like a Porche, didn't look like a Porche. In a simple view, even though it had many of the same components, it was the quality of the parts and what the designers and engineers did with the various parts that made it a VW or a Porche.

Digital cameras all have lenses, sensors, they are rated in Mega Pixels, they record the data for transfer to your computer or printer. But like cars, it is the design, the components and engineering that determine how well it will function and do the job it was created for.

The simple answer is that it needs to be good enough to do what you want it to do. Just as a car's specifications won't tell you everything about that car, neither will the number of Mega Pixels tell you if a camera is the right one for you.

My suggestion is to decide what you expect the camera to do for you. Are you going to use it to take photos to email to friends and family. Do you want to make make prints from your photos? If so, how large—4"x6", 8"x10" or larger? Are you going to be shooting sporting events? Do you want to take photos to submit to magazines and newspapers or for your company's publications?

Once you've decided what your requirements are you can compare cameras to decide which best fits your needs. A great place to start is the digital camera shoot out that was done by Samys. It will give you a comparative view of the performance of several cameras. There are also in-depth reviews of most digital cameras at dpreview.

-David McCullough

www.McCulloughphoto.com