35 millimeter adapter
A 35-millimeter adapter (also DOF adapter or image converter) is an optomechanical device that allows lenses that are normally used for 35-millimeter film or small format cameras to be used on video cameras . The point here is to realize the advantages in the area of depth of field of the 35 mm area with a conventional video camera. You can use normal interchangeable lenses from SLR cameras, but also film optics.
functionality
An image on a matte translucent disc (is a normal lens focusing screen or "ground glass") projected. A camera behind it can record this image on the back. Mostly you need a camera with a macro function or achromatic lenses in order to be able to focus the screen to fill the screen. The lens on the 35 mm adapter takes on the task of focusing (and possibly zooming). The camera is only required to film the projected image from the screen.
Screen
The core of the 35 mm adapter is the ground glass. There are two types:
Moving screen
Since a section of mostly 35 mm of the ground glass is enlarged to HD resolution, the ground glass must not have any grain or structure that is visible for HD. Many manufacturers use a focusing screen like the one used in the viewfinder on SLR cameras. But these disks have too much grain, which would be visible in the picture. The solution is to let the screen vibrate, rotate or, in the best case, oscillate, which blurs the grain and can no longer be perceived in the finished image as a static structure, but only as a far less noticeable noise.
Static screen
Some newer manufacturers offer 35mm adapters with no vibration or rotation. Higher-resolution matte screens are used, which make the emergency solution of the moving screen superfluous. However, one must always check that these adapters are suitable for HD resolution, and some static adapters are only offered for SD resolutions.
restrictions
Using a 35mm adapter has some limitations:
- Like any optical component, the 35 mm adapter also entails a certain loss of light. This can be reduced to a minimum with high-quality ground glass or lenses.
- Due to the construction and processing of some adapters, there are various image disturbances:
- Vignetting : a shadowing towards the edge of the picture
- Image defects: chromatic defects (color defects) or image warping.
- Like any lens, the 35 mm adapter rotates the image, so the image is upside down. To avoid this problem, an external LCD monitor turned upside down is usually used as a viewfinder on the camera during recording (the image can then be rotated in post-production ). Some manufacturers also offer so-called flip modules, which straighten the image again (but at the expense of the total light output and the total weight of the system).
price
The price range for 35 mm adapters is between a few hundred to a few thousand euros and depends very much on the materials and technologies used. Especially the quality of the ground glass and a possibly required flip module increase the price very much. Some do-it-yourself projects allow you to manufacture your own 35mm adapter for a few hundred euros, but usually do not deliver the quality of a commercial product.
| Manufacturer | Adapter name | system | Country of origin |
|---|---|---|---|
| Cinevate | Brevis35 | emotional | Canada |
| Cinemek | G35 | static | United States |
| Letus Corporation | Letus35 | emotional | United States |
| P + S technology | Pro35 / Mini35 | emotional | Germany |
| Muller & Wilkinson | Link.thirtyfive | emotional | Germany |
| Redrock | Micro35 | emotional | United States |
| Shot35 Ltd. | SG35 | emotional | Great Britain |