John was amazing in his readiness of reply and his exactness of memory.约翰准备充分的回答和精确的记忆令人惊讶。You can use a filter of the opposite colour over the lens, provided that you know the strength and exact hue of the colour cast.你可以在镜头外加用相反色调的滤光镜，不过你得了解偏色强度和精确的色度。