Video-enabled DSLR cameras fall short of professional camcorders for one simple reason: HDSLRs are designed for capturing stills, not moving images. One shortfall of HDSLR cameras is their lack of ability to autofocus. This alone would not deter most professional videographers from picking up the compact camera for video work, as most professionals prefer to manually focus for more control, but the three-inch LCD on the back of the camera is not a great tool for manually controlling focus.
Hoodman Hood Loupe Professional LCD Screen Loupe: Loupe systems such as the Hoodman LCD Screen Loupe can make focusing easier.This is often remedied by a loupe, an accessory that attaches to the LCD viewfinder on the back of the camera to magnify the image. These systems range from $60 to over $400 (in early 2011) as reviewed by cameratown. Professionals accustomed to using professional video cameras will be a little disappointed with this solution, as loupes only allow filmmakers to create video at eye-level; the loupe cannot articulate or be adjusted to be visible if you need to raise the camera above your head or carry it at your knees. This means you'll need a step stool to elevate yourself for higher points of view, and you'll need to crawl on your belly or kneel for lower points of view.
An advantage of the loupe is that it gives you another point of contact while shooting – this provides steadier shots, especially in run-and-gun styles of shooting. This accessory also allows for a clearer view of the LCD on sunny days, because it acts as a hood to exclude the light.
Follow Focus Systems
Genus G-SFOC Superior Follow Focus System for DSLR: The Genus G-SFOC Superior Follow Focus System for DSLR enables smooth focusing.Another problem that becomes more pronounced with HDSLRs is the inability to focus smoothly by focusing off the barrel of the lens. When you focus this way, you place your hand on the lens and turn the focus ring, which often moves the lens and creates vibrations. This may not be enough of a problem to cause concern in amateur and low-budget filmmakers, but for professionals using HDSLRs, this can be a problem that can't be overlooked.
The solution is a follow-focus system, long used in the film industry to pull focus and now available for DSLR cameras. These systems often attach to the base of the camera and extend to the focus ring on the barrel of the lens. A set of gears enable you to pull focus with a knob, eliminating the need to touch the lens to focus. These systems can be bought or made very inexpensively, as explained by Philip Bloom at his website, but professional systems can exceed $3,000.
In order to assure you have sharp focus, zoom in as far as possible on your talent, then pull out to achieve the desired framing. This will assure the subject is in focus. Focus on the talent's eyes; in some close-ups with wide open apertures, you may need to pick which eye to bring into focus.
If your lens has markers designating the distances in sharp focus, use a tape measure to determine how far your subject is away from your camera and then adjust the focus accordingly.
Don't use an aperture wider than f/4 for video unless you are sure you can maintain focus; f/4 provides excellent depth of field, yet is more forgivable than wider apertures in terms of maintaining focus.