The Smaller the Sensor Size, the Shallower Your Depth of Field

When talking about the differences between full-frame cameras and crop sensors, one of the biggest arguments in favor of full-frame sensors is the ability to produce images with a shallower depth of field. This was always my understanding of the subject as well. But after watching this video, I have seen the error of my ways. As it turns out, if all the variables are the same and the only thing changing is sensor size, the smaller the sensor, the shallower your depth of field.

I'm not going to try and explain all the science and math from the video, because the video does a much better job than I could even attempt. But my biggest takeaway from this video was when thinking about a sensor's crop factor and how that’s used to calculate a lens' equivalent focal length. Most people multiply the crop factor of a sensor by the focal length of a lens in order to get the full frame equivalent. The trick though, is that you need to multiply this crop factor by the focal length as well as the aperture.

The reason why it seems that full-frame cameras have a shallower depth of field has a lot to do with the focus distance needed in comparison to a crop sensor. The example below shows that in order to get the same frame of view on a crop sensor, you need to increase the distance of the subject. This added distance is what increases the depth of field on the crop sensor.

Who here just had their mind blown?

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I know I am super late to the party, but the truth is: The larger the sensor, the shallower the depth of field.

For example: if you look at the footage of a GoPro, do you notice how there is basically no bokeh (unless you get the lens literally right up next to a subject). Same goes for a iphone 6 (except an iphone 6 has a slightly larger sensor so you can get a little shallower depth).

The multiplication of the depth of field by the crop factor does not affect the depth of field in the same way an optical zoom works (that would be like claiming that cropping a photo in Photoshop would make the depth of field shallower).

"The Smaller the Sensor Size, the Shallower Your Depth of Field"
That statement is not true it is comparing apples with oranges!
In fact with the same field of view and aparture the depth of field on the larger of two planes will have a shallower depth of field.

Asuming two sensors with an equivalent number of pixels you apear to saying that the depth of field on a smaller sensor will be shallower this has to do with pixel density and resolution, nor have you have not taken into account that tightly packed pixels bleed in to one another and increase noise!

When all things are equal; the field of view, aparture the quality of a cameras recording plane then larger the plane the the Shallower the depth of field. So it's not true to say "The Smaller the Sensor Size, the Shallower Your Depth of Field"

Mobile phones with tiny sensors don't produce a shallow depth of field...

Hopefully someone can explain to me why I had a shallower depth of field :
My camera = Canon 70D
Settings = 18mm (18-55 kit lens); F 4.0, 1/30, ISO 400, Speedlite 600EX II-RT fired; shooting in Auto setting

Shooting next to me....
Friend's camera : Canon G16
Settings = 6.1mm; F 1.8, 1/80, ISO 400, flash not fired

It was a group photo almost edge to edge.
My friend's shot ended up sharper. Edge people still a bit out of focus...but my edge people were much more so.

The first pic is the G16, the second is my 70D.

At a higher aperture, bigger sensor, same distance, shouldn't my pic have a greater depth of field?

I don't think this is a DOF issue. I can't tell if it's out of focus, or if it's just motion blur from shooting at a slow shutter speed. The G16 was shooting a faster shutter speed, and also includes built-in image stabilization to reduce the effect of camera shake.