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。It has a red filter to view prints on printing paper without fogging it.它配有红色滤光镜用来查看相纸上的影像，不会引起灰雾。