To create an image, the screen has to be frosted, either by having some material deposited on it to scatter the light, or by being sandblasted or etched in some way. Under extreme magnification, i.e., the condenser lens, you will see a grainy pattern in the screen. That’s okay. Film has grain too, created by crystals formed by the chemical processing of the film. Except that film grain is as unique as snowflakes, so it changes on every frame of the film. The grain on the screen in your adapter is unchanging, producing an identical pattern on every frame. The resulting image will look textured, as if it were projected on a terry-cloth towel. To solve this problem, you need to set the screen in motion, either through vibration or rotation.
Now think about that. The screen has to be perfectly aligned with the lenses and image sensor in the camera, and it also has to be constantly moving.
The condenser lens can introduce another set of complications. It has to bend the light at a high angle to magnify so much, and one problem that can occur at the edges of the magnifier is that it can start to diffract the light, separating the colors out into a rainbow, resulting in color distortion, red and blue fringes, and color smearing. If the condenser is not too close or too far from the screen, then the video camera won’t be able to focus on the entire screen at the same time. And you will end up with the center being in focus and the edges being blurred, or the edges in focus and the center blurred.
Did I mention that the 35mm lens flips the image upside-down? It does this in a still camera as well, but the image is flipped upright before it gets to your eye. Framing an upside-down image is extremely difficult. Left is right, right is left, up is down, and down is up. And moving and panning shots are almost impossible with an upside-down image. The image will be recorded upside-down as well. So it has to be flipped in post, which is trivial for most editing programs, but an added annoyance. To solve this problem you can include mirrors or a prism to flip the image over, as in a 35mm reflex (through the lens) camera. But in a still camera, the image is only flipped for the user. It is still recorded upside down when the shot is taken to ensure that the quality of the mirror or prism does not interfere with the quality of the recorded image. If you flip the image in the adapter, then the mirror or prism has to be of pristine quality so as not to distort or diffract the image being recorded.
The still camera lenses from Nikon, Pentax, and Canon all use different mounting mechanisms to attach the lens. Plus, they focus at different distances and that means that depending on which 35mm lens you are using, the distance from the lens to the screen will have to be different or the lens will not focus properly.
The video camera lens, to which the 35mm must attach, comes in various sizes. For example, the Panasonic DVX uses 72mm filters, the HVX uses 82mm filters, and XDCAM cameras use 77mm filters.
Finally, I should mention that weight and size are an issue. Most video cameras were designed to hold one or two glass filters on the front of the lens. The further the assembly sticks out, the greater the leverage there is from the front of the 35mm lens back on the video camera’s lens assembly or the tripod mount point. So you will probably need to support the adapter on some kind of rails.
Now that your awareness of the technical problems that the adapter must solve is heightened, let’s take a look at the Letus 35 Extreme.
Letus 35 Extreme
Look at this smart design. The adapter uses two AA batteries. The battery door does not screw on – it is held on by powerful magnets. And the door can be removed easily with your fingernail. When you are in the field, you can easily change the batteries without fumbling with a screwdriver and using AA’s makes it easy to find more batteries when you need them.
On the right, we are looking into the camera-end of the adapter. The button that turns on the screen vibrator is located on the bottom and lights up when it’s running. This is handy because the vibration is barely noticeable, and if you didn’t have the light, you could easily leave it running and burn through batteries. It’s also smart that the light faces the camera and not the talent, where it could interfere with the shot or bother people during an interview.
