Wednesday, February 24, 2010
Shooting with a 35mm DOF(Depth of Field) Adapter can yield amazing results, especially compared to the normal look of a 1/3" palmcorder, where everything in the frame is in focus. A 35mm DOF adapter allows focus to help tell the story, by highlighting the important parts in the frame through selective focus. Here are some tips for getting the most out of our Letus Ultimate 35mm DOF adapters:
The Letus Ultimate can be mounted to most any camera, either directly to the front of the built-in lens, or via a Letus Relay Lens for cameras that have detachable lenses. Here we'll focus on palmcorders with built-in zom lenses such as Panasonic HVX200, HPX170, Sony EX1, as well as many Canon and JVC models.
Once the Letus Ultimate is mounted onto the camera's stock lens, there is a lot of flexibility in frame size via the camera's built-in zoom lens. This allows you to choose between Full Frame 35mm(35mm still camera) frame size or Academy(motion picture) frame size, or anywhere in between or tighter. Frame size affects field of view, magnification of focal length and depth of field.
Our Ultimate's are available with Nikon, Canon and PL-Mount lens mounts, allowing for 35mm SLR or motion picture primes or zooms. It's important that the lens have manual iris and focus control, the more focus rotation the better. We offer a set of eight Nikon 35mm SLR prime lenses with Zacuto focus gears for use with our Zacuto follow focus control.
Once the video camera's zoom is set for the wanted frame size, focus on the ground glass in the Ultimate. It is best to tape the focus barrel down, although taping the zoom down as well will prohibit you from using the zoom to quickly alter focal length when needed vs. taking the time to change 35mm lenses when small frame adjustments are wanted.
Press the red button to power up the Ultimate and confirm power by seeing a green light and "99" on the speed display. Always keep the speed at maximum, 99. Do not turn off between takes. The Ultimate is powered by two AA batteries or external DC power.
Set the front focus of whatever 35mm lens is mounted to the Ultimate.
Back focus on the Ultimate is the large blue ring. Loosen both silver knobs on the blue ring and turn the ring in 1/4 or more rotations, not tiny increments, with the taking lens at infinity. Use an object at least 50' away for back focus. It is best to have the 35mm lens and camera's iris wide open for this procedure.
If possible, avoid shooting with the camera's stock lens wide open. F2.8 or f4.0 will result in a sharper, higher contrast image.
Use the 35mm taking lens f-stop to choose the wanted depth of field, not for exposure. Two stops from wide open is optimal for sharpness and contrast, but shooting wide open will result in the most shallow depth of field and is an aesthetic choice. Just know that shooting wide open will make even a static head shot a challenge for focus.
Actual image exposure should be done with the camera iris and/or internal camera ND filters(for outdoors). Try to keep the 35mm taking lenses at a constant iris in order to maintain depth of field consistency.
You will use 50mm and 85mm lenses for interview single head shots, primarily. The 85mm will have more shallow DOF due to its longer focal length.
We recommend using 17" or larger HD monitors for critical focus. Also red peaking, or pixel to pixel modes, if offered on the monitor. Large monitors are more likely to show ground glass grain and flicker issues as well as dust particles.
Try to avoid light pointing directly at taking lenses which can cause flare and contrast reduction. A matte box or flags are useful light control methods.
If the above steps are taken, you will have a good experience shooting with a 35mm DOF adapter. Do know that this tool has a learning curve. Check all footage carefully--focus is more difficult than you would think. While not as easy to shoot with as a stock zoom lens, the results will be more cinematic and natural looking, and is a good complement to shooting at 24 fps. Also, 35mm DOF adapters are a great way to separate you from your competition!