This article is a part of a series about choosing a digital SLR camera:

• Choosing a Digital SLR Camera – Part 1: The basics about a Digital SLR Camera
• Choosing a Digital SLR Camera – Part 2: Resolution
• Choosing a Digital SLR Camera – Part 3: Auto Focus
• Choosing a Digital SLR Camera – Part 4: Sensor Size
• Choosing a Digital SLR Camera – Summary

Key Camera Feature: Resolution

Resolution is the most common specification that manufacturers advertise when it comes to digital cameras. In terms of digital cameras, resolutiom would be the equivalent of horsepower when marketing a vehicle, where a higher figure will almost always be more enticing for the buyer than a low number.

However, how can we determine the ideal amount of resolution our cameras should have? Are the differences between resolution figures really as significant as the advertisement claims? How does resolution amount affect our photographs?

These are important questions to ask and research upon when it comes to the importance of resolution amount in a digital camera.

What is resolution?

By definition, resolution describes the number of pixels or dots present to create a final image.

All digital cameras utilize an imaging sensor to convert the light that enters the camera lens into digital data to form an image. As light hits the sensor, the sensor captures each light beam with millions of tiny light cavities and separates the light beam into red, green, and blue channels. Then the captured information creates a completed image using the camera’s multitude of chips and processors.

The physical size of a camera sensor is finite, it cannot expand or contract in size, so there’s limit of how many light cavities you can cram onto a sensor’s surface. These light cavities are commonly known as pixels. In general, the more pixels are on a sensor, the higher the resolution of the sensor.  If we take a look at Figures 1 and 2, both have identical dimension but Figure 1 has less grids (pixels) than Figure 2. The same thing happens when a camera has the same physical sensor size but different megapixel count.

Theoretically, the more resolution a sensor has, the more detail the sensor can capture. There are millions of tiny pixels in each sensor, and they’re rounded off by the millions, hence the term “mega” pixel. For example, if a camera claims to have 5-megapixels, that means your camera has five million pixels on the sensor, therefore the final image is made up of 5 million individual pixels.

How much resolution do I need?

Digital SLRs started with a humble 1.3 megapixel sensor back in 1991, as of 2009, digital SLR have reached over 20 megapixels and its still increasing. How much do we really need? The answer is quite simple, actually, especially for the hobbyist. How large will you print?

Yes, the main issue with resolution is output print size.

Most of us will view digital images on screen, which doesn’t offer that much viewing area anyway. For example, a large, wide screen 33” LCD monitor only displays approximately 2560 x 1600 pixels, or 4.1 megapixels. We rarely view images full screen, so most images viewed on screen won’t require much in resolution. In addition, most digital photos end up being on the internet, and due to file size restrictions and download speed issues, the image files we upload on the web will require an even smaller resolution requirement.

In practical terms, the larger the displayed image, whether on screen or on print, the farther we have to be from the display to view the entire image. As we move farther from the subject, the more difficult it is for human eyes to scrutinize details as well.

The larger the print, the more resolution we need. It’s that simple. Generally speaking, the table below shows the resolution requirement depending on print size if printed in high quality.

For most camera users, a 4-6 megapixel camera is more than sufficient even for larger prints. The print size recommendation in the previous table can be exceeded if we reduce the quality of the prints. As mentioned earlier, if a print is viewed moved farther from the viewer, the details becomes less critical. In fact, even a 6-8 megapixel camera can produce a billboard-sized print with proper graphic interpolation (upsizing) software, as we never view billboards at close distances, we can clearly see that most billboards are sufficiently clear when viewed from a distance.

With the current crop of digital SLRs bottoming out at 6 megapixels, there’s really no reason to worry about not having enough megapixels for our photographs.

Why not get the most megapixels I can afford?

You shouldn’t because megapixels is just part of the equation when it comes to image quality. The sensor alone doesn’t dictate how an great the camera can translate those pixels into a final photograph.

Higher resolution sensors often cost more to purchase and also cost more to maintain. As megapixel count grows, so does file sizes. Larger file sizes would require much larger memory cards, larger computer storage space, and more powerful computer to view and edit the images. All of these will become required expenses as megapixel count in cameras increase.

We may wonder “can’t we just reduce the resolution setting in the camera and use smaller file sizes?”. Yes we can do that, but whenever we choose a file size within the camera that’s not full resolution, we’re only using part of the sensor and effectively reducing our high megapixel camera to a lower megapixel camera.

For example, a typical 8-megapixel camera gives us a large image with 3504 x 2336 pixels at full resolution, if we change our image size to “medium”, our image size drops to 2544 x 1696, which is just 4.3 megapixels. Now if we’ll only use 4.3 megapixels all the time, wouldn’t it make sense to save hundreds of dollars by buying a 4.3 megapixel camera to begin with?

There are technical issues to contend with when it comes to choosing higher resolution sensors such as noise control, dynamic range, buffer speed, etc. but in most cases, the differences are rather minor and doesn’t affect most photographers in practice.

So don’t worry too much about resolution and megapixel specifications. Any digital SLR with over 6 to 8 megapixels should be sufficient in terms of resolution requirements for most users only if you habitually print large images when megapixel requirements will be higher.

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