Crop Factor (Nikon)

It's not just the lens' focal length that affects how large a field of view you will get. Different lenses may produce different viewing angles and image angles on different cameras. The same goes for brands and camera manufacturers.

Imagine you have the lens Nikon 50mm f/1.8 D.

This lens has a fixed focal length of 50 mm which means that you can not zoom in or out. We will now do a test trying to show how the viewing angle and experienced focal length can change based on what camera you choose.

In the test we use two different digital system cameras.

Nikon D700	Nikon D90

We set up some miscellaneous things on a kitchen table, put the camera on a tripod, and take some photos.

If we use the lens on your Nikon D700 so it gives the picture below. Note that there is a lot of air around the various objects.

If we now, without moving the tripod, change the camera to our Nikon D90 we get the picture below. The air around the various motifs is now completely gone and both the dachshund and the clown have been cut.

By changing the camera, we got the same effect as if we had zoomed in on a lens.

Since the lens we used was a prime lens, without the possibility of zooming back or forth, the question is obvious - how can we get two different results with two different cameras?

The size of the camera's sensor affects the camera's field of view through the lens

Each digital system camera has an image sensor that digitally detects the image and the flow of light traveling through the lens into the camera. In the older, non-digital, cameras there were a 35 mm film and the digital sensor today fulfills the same function as the film did back then.

The images above could differ depending on how large the digital camera's image sensor is. An older system camera's classic 35 mm film had the dimensions 36.0 x 24.0 mm, but if you compare with e.g. Nikon D90 so it has an image sensor that measures 23.6 x 15.8 mm. The sensor in the digital system camera Nikon D90 has a size equivalent to 50% of its analog predecessor.

Most lenses on the market are adapted for use with both older film cameras and newer digital cameras. Although the lens has a round shape, it has a rectangular work surface inside. As you can see below, our three different cameras have different sized sensors, all marked in red below. These sensors should be the camera's eyes and that is what is looking through the lens.

Each digital system camera has an image sensor that digitally detects the image and the flow of light traveling through the lens into the camera. In the older, non-digital, the cameras were, for example, 35 mm film and the digital sensor today fulfills the same function.

The images above could differ depending on how large the digital camera's image sensor is. An older system camera's classic 35 mm film had the dimensions 36.0 x 24.0 mm, but if you compare with e.g. Nikon D90 so it has an image sensor that measures 23.6 x 15.8 mm. The sensor in the digital system camera Nikon D90 has a size equivalent to 50% of its analog predecessor.

Most lenses on the market are adapted for use with both older film cameras and newer digital cameras. Although the lens in its shape is round, it has a rectangular work surface inside. As you can see below, our three different cameras have different sized sensors, all marked in red below. These sensors should be the camera's eyes and look through the lens.

Nikon D700	Nikon D90

The lens has the same internal size all the time, of course, but when we move the lens from one camera to another, the camera and its sensor is looking through the lens a bit differently. The camera's image sensor is the eye and controls how much each camera sees through the lens.

Nikon D700	Nikon D90

The different sensors in the cameras see different amounts of the image, therefore the end result also varies. A smaller sensor see less of the object. From what the camera sees, the camera creates its image and if the camera sensor does not see the clown's entire hat or tail on the dachshund, well then it is not included in the image either. The images are cropped already inside the camera, before they are taken, if the sensor is smaller.

Nikon's different sensor types

There are two different sensor types in Niko's cameras and the different sensors are different sizes.

Crop factor

With digital cameras, people talk about something called a crop factor. The crop factor indicates how much smaller the digital camera image is. In the case Nikon D90 is 1.5x, because the analog size of the analog camera is 50% larger than the sensor in Nikon D90 and this makes us multiplying with 1.5x.

Crop factor = Perceived focal length extension

Since we get the effect of zooming when the sensor becomes smaller, we talk about focal length extension. The image angle and focal length you get with the Nikon D700 and Nikon 50mm f/1.8 D will be the same as you get with the Nikon D90 and Nikon AF 35mm f/2 D, because you then multiply 35 by 1.5x and get 52 mm.

Below you can see the focal length extension that applies to these two camera models, which represent Nikon's different sensor types.

Nikon D700	Nikon D90
FX, Full frame	DX, APS-C sensor
No focal length extension	Focal length extension 1.5x

Why is all this important to me? How does it affect me in real life?

As we talked about earlier; by changing the camera we got the same effect as zooming. With different cameras we got a perceived change in focal length. Therefore, the focal length of an lens is not always what it appears to be. A lens and a focal length of 50 mm can suddenly become 75 mm, depending on the camera used.

If in the past you had a Nikon analog camera and a wide-angle lens, this lens may not be able to provide you the same field of view and wide angle images if you use it on a newly purchased Nikon digital camera with a DX/APS-C sensor. Than that focal length will suddenly be 50% larger... or at least the viewing angle will feel that way. 16 mm will become 24 mm, and your 24 mm lens will become 36 mm and so on. The wide viewing angle may be perceived as narrower and this is not because the lens properties have changed, but because the cameras work in different ways and has different sensors. You must therefore be aware and prepared for the effect that the choice of camera might have on the focal length, before buying a new lens or camera.

Lensora will help you

On Lensora.com, we always calculate the perceived focal length for you, so that you can see how much the perceived focal length is on your particular camera when you look closer at a lens.