Resolution- How Many Megapixels Do You Need?

When deciding which digital camera to buy you will need to consider how many megapixels you need. Resolution in a digital camera is measured in pixels. Let’s look at why this can be important in your choice of camera.

Resolution- How many megapixels do you need?

Pixel stands for picture element, and digital photos are made up of millions of these tiny pixels. The term megapixel (MP) simply means 1 million pixels. So 2 megapixels would be 2 million pixels, 3 MP’s would be 3 million and so on.

Your digital camera has an image sensor that is the digital equivilent to film. This sensor is made up of pixels.

When exposed to light each pixel records a small bit of data which is then processed and the result is a digital image.

The number of megapixels that your camera has tells you how many pixels the image sensor uses to create your image. Since detail in the image is relative to the number and size of each pixel, the more megapixels your camera has the more detail it is capable of recording.

Think of a pixel as a tiny dot. Your digital print is made up of millions of these tiny dots. The larger the print, the larger these dots become. At some point they won’t be sharp little dots, but more like fuzzy circles. Detail then becomes blurred.

You can see this yourself if you have an image editor on your computer that allows you to enlarge an image. Simply take a digital photo image and enlarge it as much as possible. You will see that it becomes more and more a blur. If the image came from a 2 mp camera it will show more blur at the lower magnification levels than an image from a 5 mp camera.

Megapixels and Print Sizes

Your main concern when deciding how many megapixels you need is the size of the prints you expect to make from your digital images and how important having good sharp and clear photos is to you. For a rule of thumb just remember that the more megapixels your camera has the larger the prints you can make.

If you only want snapshot size prints for the family album, and to email to friends and family, then you will be quite satisfied with a quality 2 or 3 mp camera. On the other hand if you want to be able to make a lot of large pictures that you can frame and display then you should try to get at least a 4 or 5 mp camera.

There’s one more thing consider when deciding how many megapixels to get. If you want to be able to crop your photos, using only a small section of the image for the final print, then you may want an extra megapixel or 2 even though you are only making album sized prints.

A 2 or 3 mp camera can produce some very good quality prints up to about 4×6 inches and even larger in some cases. But if you want to make 8×10 or larger sized prints or you do a lot of cropping, then you would get better results with a 4 or 5 mp camera.

This is extremely simplified and there are other factors that determine print quality besides how many megapixels your camera has, but the important thing to consider here is the size of the prints you want from your digital camera.

While it doesn’t hurt to have more megapixels, if you don’t need them you might be happier with a high quality 3 mp camera than a cheap 5 mp one. Also, for email and display on the web you have to reduce the resolution anyway, so fewer megapixels is not a disadvantage.

If you are shopping for an intermediate level camera and know you want at least 5 or 6 mp, then you should also learn about image sensors and lens quality, since they can be very important to the quality of the camera’s images.

Just having more megapixels doesn’t guarantee that a camera will produce better quality images than a camera with fewer megapixels. If high image quality is important to you, then the number of megapixels is only one factor to consider when choosing the best digital camera.

Go to Step 3 – Which Features Do You Want?

Here’s to better photography …

Al Hannigan

Al Hannigan

Digital Camera Image Sensor

An image sensor is the digital equivalent to film in a conventional camera.

Unlike film, however, the image sensor is built into the digital camera and cannot be changed for different situations.

The most common sensors used today in digital cameras are the CCD (Charged Couple Device) and the CMOS (Complementary Metal Oxide Semiconductor).

If you want to know which kind your camera has, go to the specifications page in the owner’s manual.

The full details on how image sensors work is beyond the scope of this lecture series, but a few things that do affect your images are important, and that is what we’ll be covering here.

Complex Technology…What’s a Pixel

Image Pixels

Example of image area enlarged 1600 % to show pixels

Images created with a digital camera are made up of pixels, which are small squares of color ( or shades of gray in the case of a B&W image ). The camera’s image sensor must convert the light it is exposed to into these pixels to render an image.

Image sensors are comprised of millions of tiny photo sensors (pixels) that record the intensity of light as an electrical charge. It then converts this charge into digital information that is used to create the final image.

The data must go through various stages of interpretation and conversion, but for most practical applications it isn’t necessary to understand all the specific details.

It is important, however, to recognize that image quality can be affected by this technology, and some cameras do a better job than others.

Sensor Sizes in Digital Cameras

One factor to consider is sensor size. In most digital compacts, image sensors cover only about 4% to 7% of the image area of 35mm film. Digital SLR image sensors will generally cover from 33% to a very few that cover 100% of the 35mm film area.

Since larger sensors have larger pixels, they can record more detail and produce smoother images. Generally, larger sensors capture images with less noise and greater dynamic range than smaller sensors.

When choosing a digital camera therefore, it is important to consider the actual size of the sensor as well as how many mega pixels the camera has. A 5 megapixel digital compact camera will not necessarily have the same quality as a 5 megapixel DSLR (digital single lens reflex).

The sensor size has what is referred to as a crop factor, or a focal length multiplier. This is a number that relates the smaller sensors to a full frame 35mm area. It is one of the reasons that a full frame 12 Mega Pixel DSLR will usually create a higher quality image than a 12 MP camera that does not have a full frame sensor.

NOTE: Don’t confuse larger ‘sensor pixels’ with larger ‘image pixels’. A larger sensor pixel can collect more detail, and produce finer images. This is good. Large pixels in the photo image mean less quality and can cause pixelation…this is when you begin to see the pixels in your image. This is not good.

To use an analogy, say you have 5 million blocks and they need to fit into a .25 inch x .375 inch area (size of a typical compact digital camera image sensor). The blocks would need to be small enough for all 5 million to fit.

Now let’s say you have a 1 inch x 1.5 inch area (approximate size of 35mm film) to fit the same number of blocks into. Having more area to work with would therefore allow each block to be made larger.

The same idea holds true for sensor pixels. To fit 5 million pixels into a smaller sensor, each pixel must be reduced or compressed. This compression can reduce the amount of data each pixel can gather. This is why pixel count should be only one of several factors you compare when considering image quality.

It would be important to understand this technology for anyone doing a serious review of various digital cameras. But for most photographers it is something you need to be aware of, if only to realize that pixel count alone is not enough to assure you of high quality images. Comparing final image results is the best way to judge a camera’s performance.

Image Sensors Exposed

When you take a picture, you are exposing the image sensor to light. The data collected by the sensor’s pixels are recorded, analyzed and processed to yield a digital image that looks similar to the scene you photographed.

This complex operation is another factor which affects final image quality, and varies from one camera to another. Such matters as noise, color accuracy, sharpness and tonal range, to mention but a few, are all affected by this process.

So again, the importance to you as a photographer is best seen by comparing final results. Fortunately, there are some excellent review sites that do this for you. Therefore, you don’t need to actually test every camera yourself. But knowing a little about sensors and pixels will help you better understand these reviews.

Whenever you want to compare cameras you are considering, or learn more specifics about a camera you already own, just do a search for digital camera reviews on any major search engine to find a list of these review type sites.

You’ll locate some excellent sites that do extensive in-depth comparisons of most of the popular cameras available. They will usually have samples of actual photos taken with these cameras as well, so you’ll be able to see the level of quality each can produce.

Three of my favorites are:

dpreview.com
Steve’s Digicams
Imaging Resource

There are many others for you to choose from, but these are 3 I have used myself and am most familiar with.

Here’s to better photography …

Al Hannigan

Al Hannigan