Crop sensor vs Full-frame - What's the Difference - Image shows two DSLR cameras

What is the difference between a crop sensor and a full-frame sensor DSLR camera?  This is a question that many beginner photographers ask when they are trying to determine if they are ready to upgrade their camera bodies.  I am going to explain it in a simple non-technical way and show you why it makes a difference.  Hint:  It isn’t just about the camera body, but about the lens as well!

Crop Sensor vs Full Frame Sensor Comparison

The difference between a crop sensor and a full-frame sensor is best depicted graphically.  A full-frame sensor is a 35mm format sized sensor where a crop sensor is a sensor that is effectively “cropped”.  Here is a pictorial of what that means:

Graphic depicting the difference between a full frame sensor and a crop sensor in a DSLR camera.

As you can see, the crop sensor has a smaller sensor.  The crop factor of the sensor depends on the brand of camera you have.  Canon uses a crop factor of 1.6x and most other brands including Nikon use a crop factor of 1.5x.  

Why Does Sensor Size Matter

Image Size

The difference between the sensors matters for a couple of reasons.  First, the image size, or alternatively the image pixel count, produced by the cameras are different.  A crop sensor camera is good for making pictures that are intended for websites, social media, or prints up to approximately 11×14.  A full-frame camera’s pictures can be used to make much larger prints because the pixel count in the images is higher.

ISO Sensitivity

Crop sensor DSLR cameras have a smaller sensor, so the range of ISO will be smaller.  The sensors also tend to be of lower quality allowing the price to be lower.  A full-frame sensor is larger allowing the ISO sensitivity range to be larger.  This matters if you shoot in low light conditions.

Focal Length

This is where the difference in the sensor size makes the most impact.  To put it simply, a full-frame camera using a 50mm lens will have a focal length of 50mm but a crop sensor using the same lens actually has a focal length of approximately 75mm (this depends on the crop factor of the sensor).  This is best depicted by comparing photos.

Photo of a shoot set-up

This first photo is to show you my set-up (Ignore the messy kitchen!!!). I am photographing two Lensbaby lenses inside the light box. I did not move either the tripod or the light-box. The only changes made are the camera body. I used the same Sigma 24mm lens for both camera bodies.

Photos of two Lensbaby DSLR camera lenses

The photo above is taken with the full-frame sensor DSLR camera with the 24mm lens. This is a true 24mm focal length.

Photos of two Lensbaby DSLR camera lenses

This is the same set-up except with a crop sensor DSLR camera. The tripod nor the light-box were moved. You can see that the focal length is actually longer with the crop sensor camera. For this true 24mm lens the actual crop sensor focal length is equivalent to 38mm.

Here is a chart to show you what the actual focal length is between the two sensor types.

Lens Focal Length (Full Frame Equivalent)Canon Crop Sensor (1.6x)Nikon Crop Sensor(1.5x)

What you can see from the above table is that if you have a crop sensor camera you are getting a longer focal length than a full-frame camera using the same lens.  This can make a big difference if you shoot indoors.  For example, a 50mm lens on a crop sensor camera being used indoors may mean you can’t get everyone in the frame because you don’t have enough room to back up.  Outdoors this typically isn’t a problem as you have the freedom to move around to get the image you want.  

That concludes the differences between crop sensor cameras and full-frame sensor cameras.  If you have a crop sensor camera you need to be aware of how it affects the focal length of prime lenses so you can make informed lens purchases.  

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