Doug Kerr
Well-known member
We often hear (justifiably) about the difficulty of obtaining a proper color balance situation in a sports arena or gymnasium. The problem is exacerbated by the fact that often the general lighting has an "ill-behaved" spectrum (although that has been greatly mitigated by modern gymnasium lighting systems).
Of course, it would be conceptually best to make a determination of the chromaticity of the incident illumination "on the floor", but that is often difficult if not completely impractical.
Fortunately, the typical gymnasium situation is one that exhibits an approximation of "global illumination" (at least to the lower part of the stands). Accordingly, we should be able to get a useful measurement by using a diffuser on the camera and measuring from the stands (the lower part if necessary).
In this case, we are usually not really dealing with the dreaded "mixed light" situation (or if we are, we are basically doomed). Thus the acceptance pattern of the diffuser is not of any real consequence - the incident light on the diffuser will likely have about the same chromaticity regardless of the direction from which it arrives.
Attaining an acceptance pattern such as the "cosine" pattern (theoretically desirable for measurements made at the subject location, especially in the face of serious "mixed light)) in a diffuser is not simple (often requiring such things as a lenticular or prismatic "front end"), and the diffusers that strive for that are typically relatively costly.
But in this situation, we can use a simpler diffuser not having that feature. For example, the recently-introduced Color Parrot diffuser (now known as the ColorRight diffuser) makes no effort to even approach a cosine acceptance pattern (by intent, according to the manufacturer), and can probably be purchased at less cost than a "cosine" diffuser (such as the ExpoDisc or the Phoxle SpectraSnap), at least if we are considering lenses with larger first element diameters.
Of course, chromatic neutrality is still a need in this situation (as for any white balance measurement) and our testing suggests that the current version of the ColorParrot/ColorRight scores well in that department.
So cosines be damned. Full speed ahead!
Of course, it would be conceptually best to make a determination of the chromaticity of the incident illumination "on the floor", but that is often difficult if not completely impractical.
Fortunately, the typical gymnasium situation is one that exhibits an approximation of "global illumination" (at least to the lower part of the stands). Accordingly, we should be able to get a useful measurement by using a diffuser on the camera and measuring from the stands (the lower part if necessary).
In this case, we are usually not really dealing with the dreaded "mixed light" situation (or if we are, we are basically doomed). Thus the acceptance pattern of the diffuser is not of any real consequence - the incident light on the diffuser will likely have about the same chromaticity regardless of the direction from which it arrives.
Attaining an acceptance pattern such as the "cosine" pattern (theoretically desirable for measurements made at the subject location, especially in the face of serious "mixed light)) in a diffuser is not simple (often requiring such things as a lenticular or prismatic "front end"), and the diffusers that strive for that are typically relatively costly.
But in this situation, we can use a simpler diffuser not having that feature. For example, the recently-introduced Color Parrot diffuser (now known as the ColorRight diffuser) makes no effort to even approach a cosine acceptance pattern (by intent, according to the manufacturer), and can probably be purchased at less cost than a "cosine" diffuser (such as the ExpoDisc or the Phoxle SpectraSnap), at least if we are considering lenses with larger first element diameters.
Of course, chromatic neutrality is still a need in this situation (as for any white balance measurement) and our testing suggests that the current version of the ColorParrot/ColorRight scores well in that department.
So cosines be damned. Full speed ahead!
