What is the Difference Between a Full Frame Sensor and a Crop Sensor?

When it comes time to purchase a new camera system, inevitably the question of sensor size will come up. Full frame vs crop sensor is usually the starting point for this conversation, but that is just a piece of the puzzle. The primary difference between a full frame and crop sensors is simply the physical size of the sensor. Full frame sensors are 35mm x 24mm while crop sensors are smaller than this and can vary in dimensions. Sensors come in several sizes, have varying characteristics and wildly differing prices. Below we will look at the most common camera sensors, discuss crops sensors vs full frames and help determine what is best for you.

Panasonic Lumix G9 Crop Sensor Camera Vs. Nikon Z7 Full Frame Camera
Panasonic Lumix G9 Crop Sensor Camera Vs. Nikon Z7 Full Frame Camera

The Basics: Camera Sensors Explained

A digital camera sensor is exposed to light when you press the shutter; this is what captures image data. It is perhaps the most important piece of hardware in your camera and is equivalent to the film from pre-digital cameras. Just like film cameras offered different film sizes (35MM, 120 Medium Format, 4x5, 8x10 Large Format, etc.), digital cameras come in several different sensor sizes. Interchangeable lens cameras have the sensor directly behind the lens, whereas DSLRS hide the sensor behind a mirror (for the viewfinder). When it comes to sensors, the difference between full frame and crop is purely the physical size of the sensor. The sensors do have varying characteristics due to the size differences, but these stem from the size alone. The same technology can be used on sensors of all sizes.

Panasonic Lumix G9 Crop Sensor Vs. Nikon Z7 Full Frame Sensor
Panasonic Lumix G9 Crop Sensor Vs. Nikon Z7 Full Frame Sensor

What is Camera Resolution?

Resolution refers to the number of pixels a camera produces in an image. One megapixel is equivalent to one million pixels. The number of megapixels can be calculated by multiplying the horizontal pixel count by the vertical pixel count of the sensor. A camera that produces an image with dimensions of 6,000 x 4,000 pixels has 24,000,000 pixels, or 24 megapixels.

The physical size of sensors does not directly translate into the number of pixels. For example, a full frame 35mm x 24mm sensor can come with 12 megapixels (like a Sony A7Siii), 45 megapixels (like a Canon EOS R5) or however many pixels a camera manufacturer wants to squeeze onto the sensor. A crop sensor (APS-C, Micro Four Thirds, etc.) can contain just as many megapixels as a full frame sensor camera.

Pixel Size, Dynamic Range and Performance of Camera Sensors

Sensors of the same physical size can have vastly different pixel counts. This results in varied pixel sizes, which is measured in Microns with the symbol μm (which stands for micrometre). Large pixels are better at gathering light, have better dynamic range and produce less digital noise compared to small pixels. As an example, a smartphone camera that has 12 megapixels may have pixels measuring a tiny 1.1 microns, whereas a 12 megapixel Sony A7Siii has pixels measuring 8.4 microns. While megapixel wars grab headlines, more megapixels are not always what you want. It is important to understand your individual needs before selecting a camera based on megapixel numbers.

How Full Frame and Crop Sensors Affect Focal Lengths

Focal lengths of lenses are based on the 35mm standard. This means that a 200mm lens on a full frame camera will produce a 200mm image. However, crops sensors have what is called a “crop factor” that helps determine the effective focal length of a lens. An APS-C with a crop factor of 1.5x will result in that same 200mm lens producing 300mm equivalent images. Alternatively, a medium format camera with a crop factor of .79x will produce 158mm equivalent images when using the 200mm lens. This may sound confusing, but once you know the crop factor of a camera it is quite simple to calculate. Just remember that a full frame sensor produces images that match the lens focal length, crop sensors produce longer focal lengths and medium format sensors produce shorter focal lengths when all else is equal. Every camera manufacturer publishes the crop factors, so the information is readily available.

In practice, this can help or hinder depending on your genre of photography. Wildlife and sports shooters typically want more telephoto reach. Crop sensors are great for this, as they amplify a lens’s focal length. Landscape shooters often want a very wide field of view, which a crop sensor is not well suited for.

Camera Sensor Size Examples

How Sensor Size Affects Depth of Field

Smaller sensors produce wider depth of field compared to larger sensors like full frame or medium format. This means that if you desire a silky bokeh background, it will be easier to achieve with a larger sensor. Medium format cameras shine when it comes to narrow depth of field and are often the choice of top portrait and commercial photographers. If you are a landscape photographer and want everything in focus, then it really makes no difference as you will likely be shooting at a smaller aperture anyway.

What is the Best Camera Sensor Size?

There is no one-size-fits-all solution for this question. There are many factors that impact this decision, including budget and your genre of photography. Smaller sensors are generally less expensive than their larger counterparts. Medium format and full frame sensors contain larger individual pixels than crop sensors, which results in better image quality. Nonetheless, you can produce incredible results from today’s high quality crop sensor cameras. The best decision will be one that weighs your needs, budget and output requirements.