The Quest for Shallow DOF (Just The Wei I Am)

Rose Bud

Digital cameras - both video and still - are unable to produce the look of 35mm images. The most noticable difference is that digital images tend to be sharper. The sharpness is good and appreciated. But part of the reason why digital images are so sharp all over the frame is due to a large depth of field (DOF), i.e. objects within a large range of distances from the camera appear to be in focus. This large DOF is the result of the small CCDs in the cameras. CCDs are the "negatives" of digital cameras. Light is focused on the CCD (just like it falls on the negative of a film camera) after passing through the lens. I'll skip the math and physics, but suffice to say that the smaller size of CCDs result in the larger DOF.

But what if I want that film look? The blurry backgrounds? Bokeh - the out-of-focus regions of the image - is useful for drawing the viewer's attention to the subject. The common way is to zoom in. Another way is to use expensive prime lenes with larger apertures. Zooming in works, but what if I want that elusive film look at wider angles?

In striving for excellence, we want to make better and better video productions for the church. Professional-looking videos depend on many other factors, this film look is just one of them. But I'm interested to find out how we can achieve the shallow DOF using the cameras that we have. The ultimate goal is a solution that is cost-effective, reliable and high-quality.

The Internet provided a wealth of information from video enthusiasts who have, collectively, done extensive work over the last 4 years. Learning from them, I intend to construct a 35mm Adaptor that meets the criteria above. In the meantime, before I can get my hands on any of the high-quality components needed, I decided to make a crude prototype using things I can find around the house. This is mainly to satisfy my own curiosity and also as a proof-of-concept, showing that the principles of this solution works and will work well.

I found an old EOS zoom lens, 2 close-up filters, and a can of stale Pringles.

Read on to see what I did with them!

Basic concept of a 35mm Adaptor:
35mm SLR lens -> focusing screen -> macro lens -> video camera

Pringles cap

Pringles cap as focusing screen

Basically, I used the cap of the can of Pringles as the focusing screen. Light from the lens falls on the screen, and is projected on the other side. It works but understandably, there is severe light loss. *shrug* But it works. And it's so low-tech, it's cool.

P35A components lined up in order

P35A assembled

The image on the focusing screen is magnified, and it is this image that is recorded by the camera. Basically, the camera's own lens is fixed and just recorded what it sees on the focusing screen.

I didn't have a video camera at home, so I used my Canon Powershot G5 to take some photos through the P35A.

My Nokia 6280