Film vs. Digital Video
There are three visual attributes that make DV look different than film: exposure latitude, motion blur, and resolution. If you can control these variables, they will be less obvious to the eye and your DV will come closer to the elusive "film look"
Exposure Latitude - A key difference between DV and film is exposure latitude, which affects contrast and detail. Color negative has a usable exposure range of 7 stops, with normal exposure approximately in the
middle. Most stocks provide 4 stops overexposure and 3 stops underexposure where detail is still visible.
Video has a usable exposure latitude of 5 stops, providing 2 stops overexposure and 3 stops underexposure where detail is still visible.
Exposure beyond the -/+ limits results in tonal compression and is reproduced as either pure white or pure black, respectively. Obviously, there is a loss of detail as well. Since highlights tend to be more troublesome than shadow areas, exposure is generally geared to highlights, letting shadows fall where they may. This avoids the "burn-out" often associated with poorly shot video. Still, it's important to stay within video's usable exposure and contrast range.
Motion Blur - Film yields a slight blur in moving objects. This is known as motion blur and it results in a distinct fluidity of movement-- a prime contributor to the "film look." Motion blur is caused by film's relatively low frame rate of 24 frames per second. A telltale sign of video is its extreme sharpness and lack of motion blur. NTSC video runs at 30 fps so how can such a small difference account for the radical increase in sharpness? The reason is that there are two interlaced fields for every frame of video, so the effective rate is actually 60 images per second (= 30 fps x 2 fields). This virtually eliminates motion blur, creating an image that is a bit too sharp and devoid of fluidity (the dreaded "video look"). The answer to this is a technical breakthrough called progressive scanning, where each frame is scanned once. In other words, the frame is scanned as a single field, with no interlacing. The lower image rate reproduces motion blur comparable to film. These cameras generally use frame rates of 24fps to 30fps. 24 frames progressive, called 24p, simplifies combining video and film footage because there is a one-to-one frame relationship. The PAL version, 25p, matches the European film speed of 25fps. Many state of the art cameras have switchable frame rates and resolutions. Another benefit of progressive scanning is a dramatic increase in resolution. This occurs because progressive scanning eliminates interlace artifacts (combed edges in movement) and interline flicker (noise in fine patterns). There is a study by William E. Glenn showing that perceived resolution in progressive scanning is 50% greater than interlace scanning (Understanding Camera Resolution, Broadcast Engineering, August 1999.
Resolution - The final difference between video and film is resolution. Many filmmakers erroneously assume that film is far superior across the board. The truth is, HD has all but closed the gap. See HD vs. 35mm Film
for more. Despite this, film is still far superior to standard definition (SD) video. To minimize this disparity you
must make sure that nothing degrades the image quality when shooting. For example, improper exposure will diminish the apparent resolution of video by compressing tones and destroying detail. Arguably, the disparity in resolution has less of an impact on the look of DV than exposure latitude and motion blur. It is not noticeable to the average audience, except of when aliasing rears its ugly head. Aliasing can be minimized by avoiding fine patterns, particularly checkered and striped clothing. DV has an interesting advantage over film that may, in part, make up for its lower resolution. It can "see" in low light almost like the human eye and captures beautiful images during sunrise and sunset. In fact, gain can be boosted to +12 dB with minimal consequence. This is true for Mini DV as well.
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