Does crop factor matter in filmmaking?

Yes and no. Yes, crop factor does exist and is technically present in filmmaking. But the problem comes when people don’t understand what it’s actually being compared to. The precise number of a lens’ focal length can’t be trusted to supply the same angle of view on every single camera. This is due to the fact that different cameras use differently sized image sensors. But crop factors are generally compared to what is referred to as a “Full Frame sensor” and this comparison in the world of filmmaking is pointless and generally wrong. 

Let’s get into a little more detail here.

Before we go any further, let’s close out two messy rumors about crop factor. These rumors are circulating through the internet photography and videography communities. So let’s clear things up.

  1. Crop factor does NOT affect a lens’s focal length.
  2. Crop factor does NOT affect a lens’s aperture.

Alright, So What Does Crop Factor Affect?

It affects the amount of the frame that we can see through the camera’s sensor. The term “Crop Factor” comes from the world of photography, so again, it’s based around the “Full Frame Sensor.” This is a standard, 35MM sensor, found commonly in classic SLR cameras. If you take a photo with a smaller sensor (like most DSLR’s for example) and the same lens it will only show a smaller area of the scene.

To illustrate this, I’ve show how different cameras with different sensor sizes will see an image through the SAME LENS.

Black – Full Frame
Red – 1.3x Crop Factor
Yellow – 1.5x Crop Factor
Green – 1.6x Crop Factor

Same Lens, Smaller Camera Sensor = Less In View

A smaller image sensor will use a smaller portion of a lens’ actual image. With this, the resulting picture will have a narrower angle of view. This is what crop factor is in a nutshell. For an example, a 50mm lens on a Full frame, 35mm sensor will look roughly twice as wide-angle as a 50mm lens on a M43 sensor. So in this situation, to get the same field of view as a 50mm on that Full frame: You’d need to use a 25mm lens on said M43 camera. Either way, don’t forget the two golden rules from up above!

The Problem In Filmmaking

Here’s where the whole thing becomes an issue. Theatrical Super 35mm is the cinema standard, technically. (For example: Arri Alexa, RED Scarlet, Blackmagic URSA Mini, etc.) This camera sensor has an equivalent sensor size to APS-C, NOT Full Frame! As I said earlier, Full Frame is a photo standard. It’s also 2.6x the size of APS-C. It is incorrect to say that a 50mm Full frame lens “becomes” a 75 mm lens on an APS-C sensor. It is still a 50mm lens in every way (especially depth of field). The only thing that changes is your angle of view.

Wrong, Wrong, Wrong.

In addition, the implication that an APS-C sensor even has a crop factor is also wrong! APS-C / Super 35 are the cinema standard sensor sizes. If you happen to see Martin Scorsese mention that he used a 28mm lens on a particular shot from The Wolf of Wall Street, you DO NOT have to do a crop factor conversion to figure out what lens you would use on your APS-C / Super 35 sensor camera. Assuming that this idea of crop factor applies to all sensors smaller than a classic SLR 35 Full Frame sensor is basically just a still photography practice. It is not correlated to cinematography and/or filmmaking!

 

This has been: Does Crop Factor Matter In Filmmaking?