Shallow depth-of-field on video (part 1)

DOF = (D_f - D_n)

One of the important visual differences between something shot on video and something shot on film is the different depth-of-field (DOF). A film camera lens focuses onto an image of 35mm square (the size of the film frame), while a prosumer camcorder will focus to a much smaller 1/3″ square (8.4mm) CCD element. This allows the film lens to exhibit a smaller DOF, which means that one can choose what to focus on. In contrast, a camcorder will have a larger DOF, so everything in the shot will be in focus.

The use of selective focusing is one of the hallmarks of current filmmaking (a bit overdone and a bit of a fad at the moment as well). And this selective focusing is an important aesthetic component and powerful artistic tool in the crafting of a visual story.

So how exactly can we make a camcorder exhibit a shorter DOF?

Simply screwing on a 35mm film camera lens will do no good, as the projection area of the CCD sensors has not changed. What we need to do is to be able to project the image from the 35mm lens onto an intermediate screen and then acquire the image from that projection into the camcorder.

Thus the 35mm DOF Adapter was created!

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