Back Focus Instruction
I recently offered a back focus chart to anyone who sent me an e-mail, but, as Greg Goodwin of Jacksonville, Fla., pointed out, I forgot the most important first step in how to use it.
Set the f-stop as wide as possible. A wide open lens will enable critical focus by making the depth of field as shallow as possible. If low light is not available, try dialing in the camera’s neutral density filters or increasing the shutter speed.
Place the chart 10 to 12 feet from the camera.
Zoom to full telephoto and focus the lens normally until the “circle of confusion” (the fuzzy area in the middle) is as small as possible. Next, zoom all the way in and use the “flange focus” adjustment on the back of the lens to refocus, correcting any changes that occurred during the zoom. Check the wide angle focus again, and then you are done.
You may need to check your back focus if you change lenses or the image goes in and out of focus as you zoom.
A PDF of the chart is still available if you send an e-mail to DVTips@nbmedia.com with “Focus Chart” in the subject line.
Camera Movement Terms
A video student from Sacramento, Calif., asks, “Would you please explain basic camera movement terminology?”
There are six basic terms that I frequently hear directors mixing up, incorrectly calling for the camera operator to “pan up” when they mean tilt up, for example, or “dolly right” when they want a pan.
Tilt — Like nodding your head “yes.” The camera remains fixed in space (it can be handheld or on a tripod) but is tilted so the image moves up or down. For instance, starting at a person’s feet and tilting up to the head.
Pan — Like shaking your head “no.” The camera remains fixed in space but the image moves side to side. For instance, starting at the front wheel of a car and panning to the rear wheel.
Dolly — The camera physically moves forward or back. Often used to follow someone who is walking or to move in for a close-up. Usually requires a change in focus.
Truck — The camera physically moves from side to side. Often used to follow a moving subject. The latest fad seems to be trucking during a shot to provide movement while the subject remains still. A whole new industry has developed around producing “sliders” to smooth this movement.
Pedestal — The camera physically moves in space, up or down. It’s usually mounted on a slider or some type of jib arm. For instance, following a seated person as he or she stands up or pedestaling up with a boom from ground level to a high overhead shot.
Zoom — Not actually a camera movement, but it simulates a dolly. The camera remains still but the lens is adjusted so it appears the camera is moving closer or farther away from the subject. For instance, starting with a wide shot and zooming to a close-up.
If the lens is set up properly (see the back focus tip above) and you preset the focus at the telephoto end of the zoom, the “move” should remain sharp throughout its travel.
These basic movements are frequently combined to achieve various effects. Alfred Hitchcock famously combined dollying in and zooming out in the movie Vertigo.
A Sand Trap
The beach or desert can be a terrible place for video equipment. The blowing sand seems to get into everything and can do real damage to moving parts unless you are as prepared as Bart Collins of Miami Beach, Fla.
Before Bart heads for an assignment, he protects his camera and other large equipment by putting them in plastic trash bags. Transparent bags work best because many times the equipment can be operated without opening the bag. Small items can be sealed in plastic sandwich bags.
A small blower brush, like those used by still photographers to clean lenses, can clear sand out of moving parts on your lens. Use it often to avoid any kind of buildup.
At the end of the day, give everything a quick once over. You and your gear will be much happier for the extra attention.