3D Screen Evaluation
The following is a brief summary on the criteria for evaluating the performance of a 3D screen. There are 3 main categories under which a 3D screen should be given consideration when undergoing evaluation for use in cinema or specialty venue. The categories are: Gain, Peformance and Aesthetic appearance.
The gain (or relative brightness) is a ratio of the screen reflectivity against a perfect matte white standard. See our section on the gain and curvature of the screen for more details.
To evaluate the performance of a 3D screen, you need to measure what we call the Signal/Noise Ratio. This is a term used to refer to the screen ability to maintain polarization of projected light. The higher the S/N ratio, the better the overall 3D effect.
Testing S/N ratio.
Setup to test the S/N ratio of 3D screen sample.
What you need:
LS-100 Minolta Light Meter on a tripod.
Two linear poliarizers. (use the same types as intended for the projector and the glasses).
3D screen sample(s).
A light source (slide projector with an AC regulator for brightness stability).
Please use dark room for these tests as any stray light can affect the readings. Do not use any other light meter than the LS-100. This instrument has the resolution required low extinction readings. Also, other light meters are polarization sensitive, thereby giving false readings.
Steps to follow
Mount the light source in a convenient location.
Mount a polarizer in front of the light source lens.
Make sure your light source is capable of producing enough raw light (around 25-30 fL min).
Mount the screen sample you intend to measure in line with the light source.
Mount the LS-100 on a tripod and place the meter at 5 degrees off axis of the sample.
Mount a polarizer that can be rotated in front of the LS-100.
While the meter is measuring brightness level, rotate the polarizer until you have both the highest transmission and highest extinction reading possible.
Divide transmission number by extinction and you get what is called a 3D S/N ratio.
This number directly correlates to how well a screen maintains polarized light. You can also take reading from 10,15 or any angle. You will notice that these reading will decrease as you go off axis, as they are directly related to the screen gain itself. The following numbers are examples to help determine if you have a good or a poor 3D screen.
S/N Ratio at 5 degrees off axis
0-50 Not worth considering for a 3D screen
50-100 Will work as a 3D screen but on the poor side (bare minimum).
100-150 Most 3D screens are in this category.
150-200 Very few 3D screens at this level.
200-250 Excellent 3D screen.250-350 Superior 3D screen I WANT THIS!!!!!
If a 3D screen S/N ratio is upward of 300, and the on axis gain is not above 2.8 – 3.0; you have an incredible 3D screen.
Throughout the history of silver or 3D screen manufacturing, there have been a number of issues with regards to making this type of screen completely free of defects. Bad seams, dry spray, lacquer blush, paint striping, inconsistent gain and colour characteristics and low S/N ratio have plagued the 3D screen industry from day one.
Judgment in this area is completely subjective. Sometimes, even a bad looking 3D screen will be acceptable under 3D viewing conditions. That is because the viewer is not really focusing on the plane of the screen as they would in a 2D presentation. It is our recommendation to view a 2D presentation on a 3D screen and make the evaluation under these conditions