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MillimeterThe Craft of the HDSLR
Sep 17, 2010 12:00 PM, By Barry Braverman
How to make the most of the newest tool in the shooter's bag of tricks.
Beware of an overly narrow depth of field that can produce insufficient focus across the frame.
Narrow depth of field: blessing or curse?
The narrow depth of field achievable in the HDSLR is often cited as a compelling advantage of the hybrid camera system, and this is understandable. For years, video shooters have used selective focus to help direct the viewer's attention inside the frame. A whisker-thin DOF can also be quite disturbing, however, in the case of an actor's face where the tip of the nose may be sharp but the eyes are slightly soft. Thus, the savvy shooter understands that a narrow DOF may not always be appropriate. Still as I've seen first-hand in my HDSLR workshops for Canon and Createasphere, these cameras can be effective learning tools for educating new shooters; the narrow DOF and breadth of manual controls are perfect for students hoping to grasp the basic concepts of depth of field, shutter, frame rate, resolution, and focal length.
Is a shallow depth of field always desirable? Orson Welles' Citizen Kane did quite well using deep focus techniques almost exclusively.
The narrow DOF associated with the HDLSR does have a subtle advantage: The oversized imager and longer lenses required to achieve a normal field of view serve to reduce diffraction artifacts, a common weakness of all lenses at very small apertures. In cameras with tiny chipsets, the diffraction artifacts begin earlier in the F-stop range, so that shooting, say, with most 1/3in. cameras stopped down beyond f/4 or f/5.6 is never recommended due to the reduced contrast and resolution. HDSLRs, by comparison, support F-stops in the f/8-to-f/11 range without risk of incurring substantial diffraction problems.
At tiny apertures HDSLRs like any other camera may produce murky, washed-out images of low resolution. The large imager, however, delays the appearance of such artifacts until much later in the F-stop range.
Taming those shadows
HDSLR shooters can mitigate the negative impact of their cameras' high compression by respecting their cameras' reduced dynamic range. This means avoiding blown-out areas like overly bright windows in a dark interior set, or deep impenetrable shadows in high-contrast daylight exteriors or at night.
For city scenes at night, the Tiffen Ultra Contrast filter can help shadow integrity and reduce noise without imparting an obvious flare or diffused effect.
HDSLR shooters should therefore be sure to use adequate fill light to help lift deep shadow areas and forestall potential macroblocking and noise. I've found that a light Tiffen Black Pro-Mist or Schneider Optics Digicon can be helpful to tighten the struggling shadow areas at the bottom end of the response curve.
Continue the discussion on “Crosstalk” the Millimeter Forum.