ALR and CLR are not opposites
Ambient Light Rejecting (ALR) describes screens designed to reduce the effect of unwanted room light. Ceiling Light Rejecting (CLR) is commonly used for UST-oriented materials that preferentially reject light coming from above while accepting projector light from below.
Why UST geometry changes the answer
A UST projector sits below and close to the screen. Its light arrives from a steep upward angle, so the screen surface can use microscopic directional structures to route that light toward the audience and absorb or deflect light arriving from elsewhere.
Marketing names vary
Manufacturers use terms such as ALR, CLR, lenticular, PET Crystal, black grid and Fresnel. Compare the actual projector compatibility, viewing angle, gain and light-direction behavior instead of assuming two labels mean identical construction.
Which should you buy?
For a tabletop UST projector in a room with ceiling light, choose a screen explicitly designed for UST/CLR-style geometry. If your strongest problem light comes from the sides, investigate whether a Fresnel design or better room light control fits better.
Use PET Crystal Classic as a reference point.
It is a 0.6-gain, 160° listed-viewing-angle, 85% ALR fixed-frame UST screen.
Check current PET Crystal offer →FAQ
Can I use a long-throw ALR screen with a UST projector?
Usually that is the wrong optical match. Use a material explicitly specified for UST geometry.
Is CLR a separate technology from ALR?
CLR is best understood as a UST-focused light-rejection approach within the broader ALR category, though manufacturer terminology varies.
