2/3" (B4) Relay
1/2" Relay
1/3" Relay

Carl Zeiss 85mm ZF, Letus Ultimate, 1/2” Full Frame Relay, and Sony PMW-EX3

The Letus Relays are a specially designed lenses that allow you to remove the lens from your 1/3”, 1/2”, or 2/3” removable lens camera and attach the Letus35 adapters right to the camera body. The Relay must be used in conjunction with a Letus adapter (excluding the Mini), it can not be used by itself or with 3rd party adapters.

• Academy and Full frame versions¹⁾
• Prime lens (no need to zoom during setup)
• High speed lens, typically faster than stock lenses
• Lockable focus
• Lockable iris/aperture
• Typically shorter than stock lenses

Letus Ultimate with B4 Pro Relay

Letus Ultimate with B4 Broadcast Lens

The Academy frame relays are designed to work with academy frame lenses (Angenieux, Arri, Cooke, etc.). These Relays are set to the 1.5 academy frame size. You can use either academy frame or full frame (including SLR) lenses with this relay. If you use full frame lenses just be aware of the 1.5 crop factor of the Relay.

• 2/3” B4 Pro Version 2
• 2/3” B4 Pro Version 1 (original design) Discontinued
• 2/3” B4 Compact Discontinued
• 1/2” Relay (academy version)

The Full frame relays are designed to work only with full frame lenses. These relays are set the the full 35mm frame size (photographic frame). You can only use full frame lenses on these relays, you can not use academy frame lenses.

• 1/2” Relay (full frame version)
• 1/3” Relay

When using a full frame relay with wider angle lenses you may experience vignetting especially with less light, including closing the aperture of the lens or Relay. This is the nature of all lenses, all lenses experience light fall off as you move to the edge of the image, this is exaggerated with wider angle lenses (especially 35mm and wider). A relay lens is also a lens, so when using a relay you get light fall of from both the 35mm lens and the relay lens, this combination is what causes the vignetting. Think of it as though you had attached a 28mm lens to the end of a 28mm lens then attached that to a camera body and taken a picture. The resulting picture would have vignetting.

Here is an example of measured light fall off. The images below are of a Zeiss 28mm lens and a Zeiss 85mm, notice the light fall off is much higher on the 28mm lens. This is just the nature of lenses, all lenses will do something similar.

Click to zoom

You can download the complete technical details from zeiss on this page.
Some things you can do to minimize vignetting caused by natural light fall off are:

• Shoot with good lighting.
• Use longer lenses (50mm +) that aren't as prone to sharp fall off.
• Use high quality optics which handle fall off better.
• Use an academy frame relay (1/2” and 2/3” only) which uses the center of the lens (1.5 crop) and will not get into the fall off zone.

The Letus relays are specifically designed to work with Letus adapters and the corresponding sensor size of removable lens cameras. Even though using a 2/3” Relay on a 1/2” camera will technically work (using an adapter), it is not recommended. The reason for this is that you will have significant cropping, the 2/3” Relay has a 1.5 crop factor (academy frame) add that to the crop factor of the 1/2” sensor and a 50mm FOV becomes almost a 115mm FOV.

Letus Relays product page