depth of field - How can a Frazier lens achieve that massive DOF?

I've read in PetaPixel about this "Frazier lens" that can achieve a massive DOF. In this video is shown the capabilities of this lens and I must say I'm very impressed.

How can this lens achieve such a DOF? Most of the shots were made on a sunny day, so I'm guessing that it has a tiny diaphragm.

Anyone has more technical information about this lens?

Answer

The lens is nothing magical and does not have "infinite depth of field" as some have claimed. However it does achieve a very deep depth of field, by a combination of short focal length, small aperture and tilted plane of focus. It was developed by wildlife photographer/filmmaker Jim Frazier who was fed up with the limitations of traditional lenses for shooting wildlife subjects close up. According to Jim the device started out as a mirror on a stick attached to a camera which allowed ground level shots without the camera or operator lying on the ground. The device needed to be refined, as he found himself panning left when the subject went right, due to the mirror!

The "Frazier lens" is a really a system of lenses, the main body of which is a wide adaptor, i.e. the opposite of a teleconverter. This unit accepts one of a series of "taking lenses" of different focal lengths. These are traditional optics that have been specially modified for the system, including sealing the units to prevent dust from entering, and locking the controls (aperture is set via controls on the main lens unit).

Traditional macro lenses use a long focal length to achieve a comfortable working distance (a long focal length allows 1:1 magnification at a greater physical distance between the subject and front of the lens). A downside of a long focal length is decreased depth of field.

The Frazier lens system allows wide angle macro shots to be made. It also includes a prism element that allows the lens body to articulate in order to get close to small subjects to make up for the lack of working distance by moving the camera body further away. Here's the lens in use showing the articulation:

The lens also tilts the plane of focus (like a tilt-shift) to maximise the depth of field with respect to the ground plane (where most subjects/items of interest are likely to be).

It's worth noting that the apparent depth of field is much larger when you look at low resolution imagery such as standard definition video, as depth of field is defined as the range in which objects are "acceptably sharp". When you downsample you lose the ability to distinguish really sharp areas and thus everything can look "acceptably sharp". You too can achieve really deep depth of field with a DSLR using an ultra wide lens if you downsample your images to 0.3 megapixels.