The depth of field myth

"The larger your sensor size the shallower the depth of field (DOF)"

This is not true! I see this all over the Internet and even some professional photographers don’t get this.

The three things that is important for DOF is:

1. Aperture (larger aperture gives shallower DOF)

2. Focal length (longer focal lengths gives shallower DOF)

3. Distance to subject (shorter distance to subject gives shallower DOF)

So it is the focal length that changes the DOF when comparing different sensor sizes. A camera with a small sensor must have a shorter focal length to achieve the same field of view as a camera with a larger sensor, given everything else is unchanged.

Another statements that I have come across on the Internet is:

"a Micro 4/3 sensor isn't big enough for me" 

There are several lenses (Voigtländer f/0.95) for MFT that will give you the same, or even better DOF than for APS-C cameras. So I would regard MFT and APS-C as very similar in the possibility to get shallow DOF.

I would say that it is a benefit to use shorter lenses (along with smaller sensors) for street shooting in most situations, because it will give you the opportunity to use large aperture optics and still get enough DOF for your frame. This will let you shoot with a lower ISO value, which in turn will give you better dynamic range and colours. 

I do some shooting for sport events (especially rowing) where you are located on land and shoot the boats with a 400mm lens. I use APS-C sensor cameras and they give the same DOF as my fellow photographers standing beside me with full frame sensors using the same 400mm optics. The only difference is, I will have a 1.6x crop advantage, and hence come closer to my subjects. This means that I will crop the photo in the camera instead of later using photo editing software.

So when you hear someone saying that a larger sensor gives you shallower depth of field, please let them know the truth!