Throw Ratio:
NOTE: In the following discussion Throw Ratio (TR) is defined as:
Throw from projector lens divided by 16:9-format image width“.

Throw Ratio can be calculated in one of two ways (where T = Throw):

Based on 16:9-screen width (W):
TR = T/W

Based on Screen Height(H)
TR = T * 0.5625/H

Pincushion as a decimal fraction of screen height (PP) = 4.21/(100*{TR}^1.910963)
Absolute Pincushion: PP*H


  • Anamorphic Expansion Ratio:

1.33x nominal (varies +1%, -0.7% with throw ratio and focus distance, see Aspect Ratio Conformance)

  • Recommended Throw Range:

2.5 metres – Infinity (8.2’ – Infinity)

  • Effective lens Dimensions:

Rear lens: 78mm
Mid Lens: 116mm
Exit lens: 132mm

  • Optical Length (vertex to vertex):

131mm (5.2”)

  • Mechanical Length:

150mm, including focusing knob (5.9”)

  • Maximum Width:

150mm at exit lens (5.9”)

Figure 1. Xeit CM-4KR – Vital statistics

  • Weight:

3.1 kilos (~6.8 pounds) without stand
4.3 kilos (~9.5 pounds) with stand

  • Optical Architecture:

All Cylindrical,
5 elements (2 doublets, one singlet),
3 groups (two end lenses fixed, one moveable intermediate focusing lens)

Figure 2. An optical doublet

  • Surface Curvature Standards:

Fabricated to <0.25% radius tolerance. Actual build quality < 0.04%.
60/40 scratch and dig

    • Anti-Reflection Coating – Contrast Maximization – Stray Reflection Minimization:

Figure 3. Stray Light can lead to Ghost Images (note: competitor’s lens)

AR Coating:
Proprietary multi-coating designed specifically for wide gamut projector lamps (UHP, Xenon and LED) on all glass-air surfaces.

Internal mechanical surfaces:
Matte-anodized with micro-ridged inner barrel.
Internal rectangular mask to block peripheral stray light

  • Optical Calibration standards:

Lens elements calibrated to <0.02O of rotation (cumulative) from datum point.
Maximum cumulative lateral displacement: <0.1mm.

Orthogonality (skew between vertical and horizontal):
1mm in 3000 (0.02O, 1.2 arc minutes)

  • Environmental Protection:

Internally moisture and dust-proof
Quintuple sealed front and rear (5 x non-organic rubber “harsh environment” O-rings)

Non-organic lens coatings

Front and rear lens caps included
For out-of-beam dust-proofing and transport protection.

ISO Class 4 clean room assembly.

Packaging and Transportation
Double thickness cardboard shipping case with 60mm polyeurethane foam all around.

  • Astigmatism Performance (focus clarity across screen):

1. All measurements assume orthogonal projector alignment (centered on screen center).
2. Subtract 2% from X-axis measurements for curved screen.

X-Axis (Horizontal) at corners of screen:
Worst Case: >78% of total enclosed energy within <0.25 pixel @ TR<1.5
Medium Case: >87% of total enclosed energy within <0.25 pixel @ 1.5<TR<2.0
Best Case:  >92% of total enclosed energy within <0.25 pixel @ TR>2.0

X-Axis (Horizontal) excluding corners:
Worst Case: >91% of total enclosed energy within <0.25 pixel @ TR<1.5

Y-Axis (Vertical):
All Cases: >99% of total enclosed energy within <0.21 pixel @ TR = [any value]

Pixel Focus (Green Channel shown) to 12x channel frequency
(See Test Pattern page for more patterns)


  • Color Aberration (CA) Performance

Registration of R, G and B accurate to <0.2 pixel anywhere on screen, any TR.
Note: this color aberration performance is so low that it qualifies as “No CA”

  • Color Transmission Performance

Minimal: 2% yellow shift only, compared to original raw projector image.
Note: During fine calibration, BLUE channel only needs correction by 2%. This is well within the human eye’s compensation ability, so many users do not bother with the adjustment.

  • Contrast Loss compared to original image

On/Off: < 0.5% loss
ANSII: < 0.5% loss

  • Constant Height Performance:

Negligible change between lens-in to lens-out.

Height reduction <0.5% @ TR=1.6 (0.3% @ TR=2), when lens installed.

This equates to a maximum of 5mm per metre of screen height (0.06” per foot of screen height).

  • Pincushion:

Nominally identical to other 1.33x anamorphic lenses.

Pincushion as a percentage of Screen Height:
<1.8% at TR=1.6
<1.2% at TR=2.0
<0.8% at TR=2.5

Pincushion Calculations (assuming lens is tilted evenly):

Pincushion as a decimal fraction of screen height (PP):
PP = 4.21/(100*{TR}^1.910963) – (multiply x100 for percentage)

Absolute Pincushion:

  • Geometric/Grid Distortion:

Flat screen:

@TR=1.5: Typically 7.95% edge-to-center
@TR=2.0: Typically 4.4% edge-to-center
@TR=2.5: Typically 2.8% edge-to-center

Xeit v. Isco distortion comparison – Flat Screen only
(see Shootout page)

Curved Screen:
Pincushion and geometric distortion both corrected to within <0.5% with appropriate cylindrically curved screen (curve should be calculated based on throw ratio), independent of TR.

  • Aspect Ratio Conformance (deviation from exact 2.37:1 AR):

@5 metre (16’) throw…
@TR=1.5: +1.0%
@TR=2.0:  –0.2%
@TR=2.5: –0.75%