The Xeit CM-4KR is our Home Cinema anamorphic solution. The new model – “4KR” (“4K Ready”) – is an evolutionary upgrade from the old CM-5E model, specifically modified and factory prepared with enhanced laser calibration to better suit the new 4K optics of the latest projectors. Every “4KR” model that leaves our factory is certified “4K Ready”.
The CM-4KR is unique among Home Cinema anamorphic adapters in that it has 5 cylindrical elements arranged as three cylindrical glass lenses, instead of the usual 4-element, two-lens design. The design task was to create an adapter that is sharp and contrasty, but which reduces distortion to lesser levels than standard two-lens devices. Conformance to correct image geometry was also a design goal. Extensive research revealed that the only way to accomplish this was to introduce a third lens into the design equation.
Performance details for the CM-4KR are supplied at the Specifications page of this site.
Maintenance of Aspect Ratios
In our opinion, one of the design disadvantages of two-lens solutions is that moving the exit lens for focusing changes the AR to much across a similar range of throws. The CM-4KR has been designed to keep the image closer than two-lens designs to 1.33x expansion, no matter what the throw happens to be. Instead of one fixed entry (rear) lens and one movable exit (front) lens, the CM-4KR has two fixed lenses – the entry and exit lenses – plus a middle lens that is the movable element. We have found that this solution allows focusing to be achieved over a wide range of throws without adversely affecting Aspect Ratio (AR) as focus is changed.
As stated in the specifications, AR flat-screen conformance is guaranteed to be with the range -0.75% to 1.00% over a wide range of throws and throw ratios.
Why is low distortion important?
Low distortion is not only important in preserving image geometry. The closer image geometry is to ideal, the more evenly light will be distributed over the entire image plane. Consider a grid of 16 x 9 squares across the image plane. Ideally, each grid square will have the same amount of light illuminating it. However, if one grid square is more or less distorted than another, the light from the projector will also vary in direct proportion to the difference in distortion. This is why less distortion equals more even illumination.
High calibration standards
Having more glass in the design requires a more accurate set-up than is necessary for two-lens devices. In cylindrical adapters all lenses must have their optical axes accurately aligned relative to each other. As noted in the Specifications section, the CM-4KR has all three lenses aligned to within 1/50th of a degree (0.02 degrees) of each other, cumulative error.
Overall horizontal alignment – alignment of the three calibrated lenses to the absolute horizon – is to better than a 1 in 1,000 error, or about 1/25th of a degree.
Z-axis movement of the focusing element is accomplished by use of a precision linear guide mounted on a hard-steel rail, accurate to a maximum of 25 microns lateral tolerance.
Calibration of the CM-4KR is accomplished by use of a video-based microscope system that can zero in on image areas a small as twenty-pixels square.
Color Aberration (CA) performance
One of the most vexed questions regarding optical performance is that of Color Aberration (CA), or “lateral color” performance. The CM-4KR uses astronomy-quality glass, precisely machined and polished to 0.25% curvature tolerance to ensure that CA is no more than 0.2 (1/5th) times the width of a pixel in the horizontal direction, even at short throw ratios (see Specifications).
Stray Light Performance
All potentially reflective surfaces inside and outside the casing of the CM-4KR are first sand blasted for a perfect matte finish and then are matte anodized black to maintain non-reflective and light-absorptive standards. Anodizing is used because surface coatings such as powder-coating, sprayed enameling and e-plating tend to shed vapors and particles over time as the coating deteriorates. Anodizing is non-particulate by its nature and thus cannot shed anything that may affect lens quality.
Additionally, the inside of the main adapter barrel is finely ribbed at right angles to the beam to disperse further stray reflections.
Lastly, the middle lens is rectangular in shape, cut to provide an effective “light trap” that stops much stray light from the projector in its tracks before it reaches the exit pupil of the adapter.
These measures, taken together – CA minimization, stray light reduction via surface treatment and mechanical baffling – enhance on-screen contrast to the maximum possible.
The CM-4KR comes with a table-top stand that allows vertical movement, horizontal tilt and rotation of the lens for on-site alignment purposes. The stand base plate is CNC machined to be simultaneously compatible with the industry standard CineSlide motorized lens transport.
Each lens is packed with comprehensive instructions for cleaning mechanical and optical surfaces, and includes a free pack of laboratory clean-room standard, single-strand cotton lens cleaning wipes.
A full, illustrated operations manual is also provided with each unit.