Sensors explained | The megapixel myth

The megapixel myth: why less is sometimes more

For years now, many camera manufacturers – and retailers – have told consumers that the more megapixels a camera contains within an image, the better. People have consistently purchased a camera based on this claim, however, the problem with this claim is that it’s false…

The number of megapixels contained within an image does not dictate the quality of the image taken in the frame; rather, it is the size of the image sensor on the camera that dictates the quality of the image taken. Image quality is more complex then, as it depends upon the relationship between the image sensor size and the megapixel number.

If a picture is taken on two cameras with an identical megapixel size, eight for example, the quality of that image would depend on the sensor. This is because a larger image sensor can capture more available light within the frame – and it is the light within the frame that contributes towards the overall sharpness of the image, which is not dependent upon the number of pixels within the image.

A useful comparison to make is that of the old film cameras; the larger the film (35mm) the better the image quality, for those with a smaller film (16mm) the worse the image quality – because those films captured less light. Therefore, a modern ‘full frame’ DSLR camera can capture the most available light, alongside the APS-C type DSLRs – these cameras tend to take greater quality images because of their image sensor’s capacity for light intake compared to a ‘point and shoot camera’ or a simple mobile phone camera. 

When a photographer starts to crop, or enlarge an image, this is when the image sensor becomes important. Photographers should aim to have an image sensor that can capture more light, as opposed to a greater number of pixels within the image. Cameras that cram a greater number of pixels into a smaller image sensor create images that are prone to developing noise (blurriness or visible grain) and less dynamic range within the frame, compromising the photographer’s ability to enlarge the image or crop the image once it is taken.

The sharpness of an image is less to do with the number of megapixels it contains, but more to do with the amount of skill it takes to take the image. Sloppy technique, or the amount of motion contained in the frame, can blur an image more than the width of a microscopic pixel contained within an image. So, a clean shot produced by a 3-megapixel camera will be clearer than a picture taken with an 8mp camera with the same image sensor if there is disruption in the shot when it is taken.

When it comes to modern digital cameras, most can print a decent quality image at any size – irregardless of the number of megapixels. If you’re printing standard sized images, then you need 100 – 150 DPI (dots or pixels per inch) to take a sharp image, which means that with a 6mp camera, images can be printed to a size of up to 30 inches and they will still look sharp. However, if you want to achieve pure-clarity with extra sharpness in the image, go for a camera with 300 DPI. Always remember, to get the perfect image you’ll need to evaluate both the image sensor quality and the number of megapixels to ensure that the images, and the camera, are right for you and the photographs you’re going to take. 

  • By Matthew Ward
  • 16 Jun 2017

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