CurtPalme.com Home Theater Forum

[Nashou66]

I always knew placement of the meter was important but here is a great explanation from the the spectracal web site with a chart or list of the viewing angles of most of the popular meters.


Darrell Bird
Lab Director, SpectraCal
02/01/2012

A meter’s viewing angle is not really something we need to be concerned about when dealing with transmissive illuminate displays, like flat screen TVs, since the meter is typically either in direct contact with the screen or very near it. However, when we’re calibrating projectors, knowing the viewing angle of your meter is critical. For projectors, we have two main concerns when deciding where to place the meter. We need the meter to be far enough back that it doesn’t cast a shadow on the area of the screen we’re reading from. But we also want the meter to be as close to the screen as possible so that we’re not adding inaccuracies such as off angle light or gain differential. Hopefully it goes without saying that we only want the meter to read from the luminous pattern and not any of the surrounding black area. In deciding our meter’s placement, we must make a compromise regarding these opposing factors and in doing so we must know the area of the screen that the meter is reading. In determining this area, knowing the meter’s viewing angle is critical.

So here’s the problem: The viewing angle is not always listed in a meter’s specs and when it is, it’s often ambiguous and based on absolutely ideal conditions. What we’ve done to ameliorate this situation is to run our own test to determine the viewing angle for our most popular meters and make these results applicable and useful to your everyday projector use. These numbers may differ from published specs since it is often not clear exactly what the published spec is referring to. There are three main attributes that are relevant: The full width at half max angle, the total light termination angle, and the general shape of the light response as a function of the angle.

Shape of light response – There are two main shapes that are typical for a meter’s light response. One is a plateau shape that has a maximum response range that is flat on top and quickly drops to zero at a certain point on each end. The other shape approximates a Gaussian curve which smoothly transitions from zero light response up to a maximum light response and then symmetrically back down to zero. The Gaussian response is far more typical but may not be as desirable. The wider a Gaussian response is, the more susceptible the meter is to off angle light.




The chart is in the article.

http://store.spectracal.com/article-why-viewing-angle-is-important


Athanasios

[kal]

Yup.

I simplify all this in my Greyscale for Dummies guide by simply stating that the meter should be positioned such that the light reading is the highest. Pretty simple.

Kal

[kal]

Yup.

I simplify all this in my Greyscale for Dummies guide by simply stating that the meter should be positioned such that the light reading is the highest. Pretty simple.

Kal