Crop Factor Calculator

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Crop factor is a term used to compare any camera sensor with the traditional or more standard 35mm camera sensor. Crop factor calculator helps to calculate equivalent focal length for a given sensor when compared to focal length when used with a 35 mm sensor.

With so many camera systems around you will see the term crop factor in many specifications , marketing literature , expert reviews. You will also here a lot of different numbers for this crop factor.

If you are not sure about what is crop factor and how it affects your photos then you are bound to get confused.

In this article we will see in brief what is crop factor and introduce the crop factor calculator which you can download and use for your own purpose.

Crop factor is generally less than one but in some typical cases it can be less than 1 as well. We will also see in this in more detail.

What is crop factor ?

The lens when fitted on camera captures the scene in-front and makes it available for the sensor to capture. Traditionally film cameras were used for all photographic purposes and the traditional size of the film was 36mm x 24mm.

The image formed by the sensor is circular in nature and the sensor captures a certain portion of this image. The bigger the sensor the wider the image and the smaller the sensor the narrower the image.

Below image explains this phenomenon. As you can see , a standard 35mm full frame sensor captures a wider image while a smaller crop sensor gives a narrower image and it appears to be zoomed in.

crop factor

Because of this for a smaller sensor the image appears to be zoomed in or focal length is increased.

The factor by which the given sensor is smaller or larger compared to a standard full frame sensor is known as crop factor. The name crop comes from the fact that the image is “cropped in” compared to complete available image smaller sensors.

The same factor is also known as focal length multiplier factor. This is because the smaller the sensor the higher the focal length appears. The crop factor can be used to multiply the given focal length to calculate equivalent focal length.

Same lens ( Prime or Zoom) when used with different camera sensor types gives you different focal length equivalent images.

The same logic is also applicable for film cameras. Here is an example of a canon film lens used with various sensor sizes.

crop factor for different formats

Crop sensor is a term commonly used for sensors smaller than full frame sensor. You can use our crop factor calculator or equivalent focal length calculator to understand what crop you will get by using a certain lens and camera sensor combination.

Crop factor calculator

Crop factor calculator or equivalent focal length calculator is a simple tool which takes in to account the given sensor size in comparison with standard full frame sensor and then calculates the crop factor and equivalent focal length.

This calculation is applicable for DSLR as well as mirrorless cameras.

How to calculate crop factor?

The crop factor can be calculated by dividing the diagonal length of the 35 mm camera sensor with the diagonal length of the camera sensor under consideration.

The diagonal is considered rather than length or width of the sensor as this also takes into account various aspect ratios of the sensors.

Digital camera sensors come in a variety of different aspect ratios or form factors. To identify what image size they can capture for a given lens it is necessary to use the diagonal as reference for calculation of crop factor.

crop factor calculator formula

For example a Canon APS-C sensor has a diagonal of 26.68 mm as against 43.26 mm for a standard full frame sensor. The ratio of 43.26 to 26.68 is 1.62 which is the crop factor for a typical Canon APS-C sensor size. canon 80D and Canon 90D are some great examples of canon crop sensor cameras.

Below table gives you the crop factors for typical sensors. There are medium and large format cameras, which is supported by our crop factor calculator. These cameras have sensors or film size larger than the 35mm full-frame size, so the crop factor is less than 1.

crop factor calculator
Crop Factors

Lens equivalent chart

The table below gives you equivalent focal lengths for various popular focal lengths used in photography. Lens equivalent chart below gives you equivalent focal lengths for different crop factors.

crop factor calculation
Lens equivalent chart

How to use the crop factor calculator?

The crop calculator is very easy to use. Following are the steps in detail ..

  1. Download and Open the excel file “crop_factor_calculator.xslx
  2. Select the camera sensor you are using. Most of the sensors are available in the pulldown menu.
  3. Crop factor will be automatically calculated
  4. Enter the focal length of the lens and F value you are using , based on the crop factor the equivalent focal length and F-stop value will be calculated is also calculated.

How crop factor affects depth of field ?

The crop factor affects the depth of field . This is mainly because the F value also increases with same crop factor. So a 50 mm F1.2 lens used on a APS-C sensor with crop factor of 1.62 will result in 81 mm F1.91 .

This means that you will lose on shallow depth of field or bokeh effect on a crop sensor camera. Hence a full frame camera is always preferred if you want a shallow depth of field and nice bokeh effect.

Thus using a lens on crop body makes it slow and you will have to alter the shutter speed and ISO to get the same effect.

The crop sensors also have inferior low light image quality and the images may turn out to be grainy in High ISO , low light situations.

Final Words

Crop factor is the factor by which the image appears to be zoomed in for a small size sensor as compared to a full frame sensor.

Crop factor calculator is a simple tool which helps you to calculate the equivalent focal length and F value for any lens of your choice for any type of camera sensor size.

You can download and use crop factor calculator completely free.