FX vs. DX Sensors

A man testing Nikon d850 camera at the exhibition.

The format sensor is the most important part of a digital camera, as it is directly responsible for capturing an image. Debates around DX and FX sensors are not “which is better?” matters, but matters of “which do I prefer?”

If you are not as technically minded as the professional photographer and would like to know what the debate is all about, then you are where I was a few weeks ago. Follow me as I take you through the maze of technology without getting stuck in a gobbledygook!

Table of Contents

1. What is a Format Sensor?

A hand holding a small digital camera sensor.

Even with all of the latest advancements in sensor technology, cameras are not close to seeing the range of light that the human eye can see in various environments. But cameras function – in a way – just like the human eye.

The lens of the eye gathers light and passes it to the iris (the colored part of your eye). The iris acts as a filter: it contracts when the light is too bright so that the excess light is screened out. Conversely, it dilutes when there is not enough light to let more light in.

Whatever amount of light the iris allows through proceeds to the retina, which – in a certain sense – is also a filter.

The retina is light-sensitive: when there is too much light, it decreases its sensitivity. On the other hand, if there is not sufficient light, it increases its sensitivity.

Why is the purpose of this manifold “filter” arrangement in the eye? It is so that we can capture an image whether there is a little light or a lot of light.

Format sensors in a digital camera are directly responsible for capturing an image. They each contain millions of pixels (similar to the pixels of a computer screen, but where the pixels in a computer screen display light, the pixels in a format sensor are there to collect light).

A digital camera with 36 megapixels means – in plain language – that the format sensor of this camera contains 36,000,000 pixels that all work together to gather light.

Once an image is captured, the format sensor data is passed on from the format sensor to the image processor. The image processor assembles the digital image from the first pixel to the last in a matter of milliseconds!

As the size of the format sensor in a digital camera decreases, so does the number of pixels – and of course the quality of the image.

The FX vs. DX debates started around this point:

  • Larger pixels work best for sensors, but they are also more expensive to manufacture.
  • In their quest to make this technology available to more consumers, manufacturers produced smaller sensors because it is cheaper to do so.
  • As the size of the sensors decreased, so did the number of pixels.
  • To remedy this situation, manufacturers have been cramming more and more pixels into tiny sensors while – at the same time – increasing the efficiency and throughput of each pixel.
  • This resulted in a “megapixel race” among the manufacturers. There are more and more pixels on modern digital camera sensors, the size of the sensors has remained more or less the same.

2. What Do FX and DX Mean?

Close-up of a full-frame camera with long lens on a wooden table.

When Nikon entered the digital camera race, they introduced a smaller sensor with 2.66 megapixels to make the camera more accessible at a lower cost. They called this smaller sensor “DX”. It produced a cropped, “magnified image”. In low-light situations, this was not effective for capturing a good quality image.

A sensor with increased size was introduced: the FX, with higher sensitivity levels without introducing much noise and artifacts, while simultaneously being able to yield better dynamic range.

This essentially means that a film camera and a full-frame digital camera, both with 24-70mm lenses on them would produce a similar field of view, not a magnified, cropped one like with DX sensors. For more detail on the subject, you can visit here.

3. Can FX and DX Be Used Together?

Woman in sportswear using her smartwatch.

How about mixing up the two types of technology? One question that is often asked, is: “Can FX lenses and DX lenses can be used interchangeably?”:

  • If you went from an FX camera to a DX-format DSLR, your full-frame FX lenses will still work. On a full-frame FX-format camera with a DX lens mounted, the camera will automatically engage its built-in DX crop mode, thus recording an image only from the center section of the sensor.
  • If you are upgrading from a DX to a full-frame FX-format camera you can still use DX lenses. The camera will automatically compensate. However, to avoid vignetting, the DX crop mode is automatically selected by the camera when a DX lens is attached.

4. FX and DX Pros and Cons

A hand grasping digital contents.

FX Sensors have better lowlight performance, and in these conditions better picture quality (that can be contributed to its larger pixels. It also gives more control over the photographer’s depth of field because it allows closer proximity to the subject. It also gives “true angles” or focal lengths, and has a higher dynamic range.

On the other hand, it also has several disadvantages:  The cameras are typically more expensive, bigger and heavier. If you want to use lenses for smaller sensors, you will get cropped images automatically. Edge softness and vignetting (darkening around the edges) can occur.

DX Sensors (cameras as well as lenses) have lower prices. Cameras are smaller and lighter and have a telephoto effect. The DX is versatile in that it can use smaller, or larger lenses. Images are sharper, with less vignetting (darkening) around the edges.

From a disadvantage point of view, one should note that low-light performance is inferior to FX. It has a lower dynamic range, a lack of “super-wide” lenses, and a small viewfinder image.

Conclusions

It is clear that the types of sensor technology are different in many respects, but also that they are compatible in terms of lenses. It is also clear that both have strong points for certain types of photography and disadvantages for other types.

Perhaps the debate is the same as in sports, where poor performance is often blamed on poor equipment. One seasoned photographer summed it up very well:

My father used to tell me, “Some of the world’s greatest photographs were taken with a cardboard box (pinhole camera).” This is true. Pulitzers have been won with photos taken with $20 plastic cameras. Point-and-shoot disposables have captured exquisite beauty. 

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