Say NO to small f-stops!

Written by Barry Braverman

Do you think smaller apertures always lead to sharper images? Think again, as explained by Hollywood cinematographer Barry Braverman.

The bending of light through a pinhole-size aperture produces a multitude of tiny light sources, which can create internal reflections and a concomitant increase in flare. Under such conditions, bright daylight scenes may appear washed out and lacking sharpness and resolution. One-third inch and smaller sensor cameras may exhibit severe diffraction at apertures smaller than f4 - f5.6. Larger sensor cameras and DSLRs may also exhibit a noticeable softening and lowering of contrast but not until f11 - f16.

It is important to maintain a proper f-stop because shooting at a narrow aperture with a 1/3-inch HD camcorder like the Panasonic PX270 or the Sony Z7 may yield images not much better than standard definition. With this in mind, some low-end camcorders with tiny sensors automatically apply neutral-density in bright conditions to avoid the narrow apertures that can lead to the loss of resolution and contrast.

Fig 1 SkiDiffractionZoe scaled

This scene recorded at minimum f-stop appears washed out due to severe diffraction. The use of a neutral density (ND) filter under such conditions is therefore imperative.

Fig 2 Diffraction scaled

At tiny apertures the edges of the iris appear to glow and act as tiny light sources that scatter the light and lower contrast.  This is a good reason to shoot early or late in the day, when larger f-stops can be employed.

Fig 3 Magic Hour scaled

Shooting at so-called Magic Hour at dawn or dusk can dramatically improve the look and performance of any camera or lens system.

Fig 4 ND Switch CU scaled

The neutral density switch at the side of your camcorder is there for a reason. Use it!

Tags: Production

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