The term “crop factor” has been among the most memorable aspects of conversations surrounding photography.

For beginners, it’s a concept they can’t seem to wrap their heads around.

That’s why this article adopts a bird’s eye view approach to making sense of what crop factor is. 

So, if you’re not sure what it means or you’re unclear about a few things, stick around as we provide you with a better understanding.

The backstory behind Crop Factor

Before the digital photography era, film photography made use of a 35mm film. 

It became popular among hobbyists, travelers and the average photographer. Thus, making it the standard film for photography. 

However, as the digital era emerged, most camera manufacturers in a bid to reduce cost modeled their sensors to the 35mm but reduced their sizes.

Also, another reason for creating the new DSLR cameras with smaller sensors was to overcome technological challenges. 

As the digital age ushered in these DSLR cameras, new problems were born; Back in traditional photography, pairing a  lens of 50mm focal length with a camera film of 35mm would produce a “normal” image. Making the 35mm become known as a “full frame”.

However, as these new cameras were made, they came with smaller sensors than 35mm. This resulted in the reduction of the field of view and image size.

So, when a lens of 50mm was paired with them, rather than getting a “normal” image, the photos appear cropped or chopped off .

Different brands have their ways of differentiating between a full frame camera (35mm) and their crop sensor cameras. For example, look at this:

Here is a great illustration of various sensor sizes from Wikipedia:

The problem created

To help you grasp why this became a problem in the photography community, we’ll explain how the various parts work together and use a few pictures to explain. 

A camera lens projects a circular image towards the back of the camera. However, because the sensor or film is rectangular, a rectangular portion is recorded when the image hits the sensor or film.

Now, a standard and traditional 35mm film will create a normal image.  But the digital cameras due to their smaller sensors will cause the image to appear cropped or “zoomed in”

This resulting effect caused confusion and raised questions- if a particular lens can produce different images on different cameras,  how can photographers know which one is best suited for them?. Plus, how can they determine what field of view they’ll cover on different cameras?

To tackle this problem, crop factor was created.

What is Crop Factor?

So you know why the crop factor was created – which is to help photographers predict what the field of view of a lens would look like compared to a 35mm full frame camera.

To put that in a simpler definition, crop factor is the size difference between a 35mm film frame and your camera’s sensor. Pretty straightforward right?

For example if your camera has a crop factor of 3, it just means a 35mm full frame is thrice as large as your camera’s sensor. The higher the crop factor, the more “cropped” the image will appear. 

Remember the goal of the crop factor is to enable you to determine what the field of view of a lens will look like compared to a 35mm full frame camera.

To do this,  you’ll need to calculate the equivalent ” focal length of a lens. This is done by multiplying your camera’s crop factor by the focal length of your lens.

Time for another example. If you have a camera with a crop factor of 1.5x and a camera lens of 26mm, to get the equivalent local length of your lens will be 1.5 × 26 = 39mm.

This basically means that your 26mm lens will act like a 39mm lens in terms of field of view.

How To Calculate Crop Factor 

So, how exactly is the crop factor calculated?

By simply dividing the diagonal length of a 35mm full frame by the diagonal length of your camera sensor.

Crop Factors And Equivalent Focal Lengths.

The following table below shows common focal lengths and crop factors with the corresponding equivalent focal lengths. 

35mm	1.5x	1.6x	2.0x	2.7x
14mm	21mm	22.4mm	28mm	37.8mm
18mm	27mm	28.8mm	36mm	48.6mm
24mm	36mm	38.4mm	48mm	64.8mm
35mm	52.5mm	56mm	70mm	94.5mm
50mm	75mm	80mm	100mm	135mm
85mm	127.5mm	136mm	170mm	229.5mm
105mm	157.5mm	168mm	210mm	283.5mm
200mm	300mm	320mm	400mm	540mm

Equivalent Focal Length

This  is the  most misunderstood part of all this. One thing you have to realise is that the focal length is the physical property of a lens and it doesn’t change no matter the camera sensor.

So, keep it at the back of your mind that a smaller sensor does not make your lens longer. Rather, it simply crops out parts of the image.

Benefits of smaller sensors. 

One thing small sensors revealed to manufacturers is how much space the regular 35mm was wasting.

Most times, photographers didn’t need to  capture a very wide field of view. They noticed edges of the frames weren’t being used. This sparked an idea and then, a trend.  Manufacturers started creating smaller sensors and lighter lenses.

Today, more and more lenses are designed specifically for smaller sensors. 

Here’s a short list of crop sensor lenses from various brands:

• Nikon : DX
• Sigma: DC
• Canon: EF – S, EF – M
• Samsung: NX

Same Mount, Different Lenses.

Some manufacturers over the years have decided to make cameras with the same mount size but lenses designed for various sizes.

Take for example the Nikon F mount designed for mounting of both 35mm full frame and DX lenses.

To close off, the best camera lenses are usually full frame lenses. That’s why they’re usually on the higher side when it comes to price.