Letus35 Adapters
How they Work
Another way to visualize how they work is how Ryan Connolly put it. Just picture videoing the movie screen at the theatre, not that you should EVER do that, you naughty! You should, however, go out and make your own movies with a Letus, they will probably be better than most of Hollywood's anyway!
Image Orientation Correction (IOC)
All Letus adapters contain IOC prism technology which means the image is flipped upright, there is no need for flipping the video in post, or rigging special preview monitors.
Our IOC prism is not only for flipping the image, it also provides a longer optical path between the camera sensor and ground glass. This allows us to obtain a much sharper image in a shorter adapter body. For example, close one eye and hold your finger in front of the other. Keep it about one inch away and see how blurry it is. Now move your finger back about a foot and notice how much sharper it becomes.
Field of View and cropping
The ground glass of the adapters is larger than the projected image of a full frame 35mm lens. Therefor when setup correctly, there is no cropping and the field of view does not change.
Modular Design
The Letus35 adapters have a modular design which means that a single adapter can be used with many types of lenses and cameras. You do not need to purchase a adapter for each camera that you plan to use.
Back Focus?
Back focus simply means the distance from the ground glass to the lens' focal point. The focal point of the lens needs to be at the right distance to the imaging plane (GG) so that you can achieve infinity focus. When this distance is incorrect you will not be able to achieve infinity, and if it is extremely far off you will have many other problems with your images.
Image Courtesy of Wikimedia Commons
Back Focus can be adjusted on all Letus adapters, on the Mini and Extreme back focus can be adjusted both on the lens mount and by changing the position of the ground glass. On the Elite and Ultimate back focus can be adjusted on lens mount and by adjusting the back focus ring.
How to adjust back focus on the Extreme (and Mini)
How to adjust back focus on the Elite and Ultimate
Back Focus Ring
The back focus ring is a feature that allows you to easily adjust back focus without needing to manually adjust the ground glass position. You simply loosen the locking screws and adjust the ring until back focus is correct. The back focus ring is included on the Elite and Ultimate and is available as an upgrade for the Extreme, it is not available on Mini.
Optimized Achromat
The Optimized achromat that is included in the Letus Elite and Letus Ultimate is a special lens in the back of the adapter that resolves the issue with Edge to Edge focus on cameras that have offset image sensors such as the: Sony PMW-EX1/EX3 and the Panasonic AG-HVX200/HPX170. This achromat is also available as an upgrade option on the Extreme. The best way to determine if you have the optimized achromat is to carefully remove the achromat and compare it to the image below.
How to remove the rear achromat
Optimization Kits
The Optimization kits for the Sony PMW-EX1/EX3 and Panasonic AG-HVX2001) are designed for the Letus Extreme adapter. These kits include the optimized achromat and the specialized thread ring for the camera. The special thread ring has a shallower collar than the standard thread ring. These kits are not needed for the Elite or Ultimate adapter since these adapters already include the optimized achromat. All you need is the appropriate specialized thread ring when using the Elite or Ultimate on the EX1/EX3 (77mm specialized) or HVX200 (82mm specialized).