Size Matters: Why large sensors are the way to go

Size Matters

Contrary to popular belief, it isn’t always about megapixels. Say you have a compact camera, a micro four-thirds, and a DSLR, all billed as having 12 megapixels. You might be surprised to discover in this little experiment that despite having the same megapixel count, there’s still a huge difference in quality among the pictures taken with the three different cameras. Grab your hankies, as we’re about to go into the nitty gritty of image sensors and why size matters.

An image sensor is found in all digital cameras, whether it’s built into a smartphone or inside a bulky DSLR. It is the digital equivalent of film on an analog camera, and like film, it is a specification that you cannot change or tweak. A sensor contains photosensitive diodes that record light or photons. It transforms them into an electrical signal that displays color, tone, highlight and shadow, and stores the recorded light data as a set of numbers that correspond to pixels. Pixels come together to form a single photo, ultimately creating a digital image file.

There are two general types of sensors: charge-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS). Most digital cameras make use of CMOS sensors, but they vary in size. We have full-frame sensors, which are as big as a single frame of 35mm film, employing the 24x36mm format. This kind of sensor produces smooth, vibrant, high-quality images, which is why they are usually equipped in pro-level DSLRs that come at a steep price.

Micro four-thirds cameras have sensors that measure 13×17.3mm—nearly half as big as the size of a full-frame sensor—packed into a compact body. This is possible because micro four-thirds cameras do not make use of a reflex mirror that can be found in DSLRs. Smaller cameras—particularly point-and-shoot models—have smaller sensors, delivering both portability and affordability.

Now we go back to our main point: sensor size matters. It isn’t always about how many megapixels you’ve got in your camera, it’s whether your sensor is able to accommodate the number of megapixels. Simply put, a small camera does not have room for a large sensor. So if you’ve got a small point-and-shoot camera with 16-megapixels, that means 16 million little pixels are crammed into a tiny image sensor, thereby depleting image quality, low light performance and dynamic range.

Full-frame sensors also feature no crop factor. We’ll save the lengthy explanation of crop factor for some other issue, but the gist is that the amount of cropping depends on how big your sensor is. This means that if you have a small sensor, your image appears cropped—as if you’ve zoomed into the scene, even if you haven’t. The quality of the image is greatly reduced because of the lack of detail within images taken by cameras with small sensors.

The principle is this: the larger the sensor, the more information it can store. The ‘information’ being referred to here are the intricate details in a digital image. Images that look sharp onscreen may not be as sharp when you print them out. Whether or not the details are clearly defined can be evidently seen on print (or if you zoom in on the image in Photoshop). Print the image out—blow it up if you have to—and observe the details of the image, particularly the shadows. You’ll see that the details are pretty fuzzy and are plagued with digital noise.

Digital noise is the modern day equivalent of grain in film, prominently found in dark sections and single-toned areas of your image. It normally shows up when you crank the ISO of your camera over 800. If you’re not familiar with the whole concept of ISO, here’s how it works: when you increase the value of your ISO, you increase the sensitivity of your sensor to light. The advantage of having a large sensor is that it acquires less noise, even at higher ISO settings. The reason behind this is because the photosites have enough space to be further apart, so there is less contamination of electrical signals. What happens to the images, then? Even if you increase the level of your ISO, the camera will still be able to produce smooth, rich, high-quality images with better gradation.

Having a large sensor expands the range of light the camera is able to capture, thus optimizing the device’s performance in low-light conditions. It also increases the camera’s dynamic range. Dynamic range is basically the measurement of the range from highlight to shadow. Ultimately, the more range the sensor has, the better quality your images will have.

Knowing the advantages and disadvantages of having large and small sensors will truly help you understand what your output is going to look like and how your camera will perform. If you’re serious about photography and are looking to buy a camera that will uphold your craft, being picky about details like image quality, digital noise levels, dynamic range and crop factor is definitely a good thing. Sure, cameras with large sensors are costly, but weigh the options; think about what going big on sensor size can do for you.


This article was originally published in the April 2013 issue of Gadgets Magazine.