-#define EM28XX_R20_YGAIN 0x20
-#define EM28XX_R21_YOFFSET 0x21
-#define EM28XX_R22_UVGAIN 0x22
-#define EM28XX_R23_UOFFSET 0x23
-#define EM28XX_R24_VOFFSET 0x24
-#define EM28XX_R25_SHARPNESS 0x25
+#define EM28XX_R20_YGAIN 0x20 /* contrast [0:4] */
+#define CONTRAST_DEFAULT 0x10
+
+#define EM28XX_R21_YOFFSET 0x21 /* brightness */ /* signed */
+#define BRIGHTNESS_DEFAULT 0x00
+
+#define EM28XX_R22_UVGAIN 0x22 /* saturation [0:4] */
+#define SATURATION_DEFAULT 0x10
+
+#define EM28XX_R23_UOFFSET 0x23 /* blue balance */ /* signed */
+#define BLUE_BALANCE_DEFAULT 0x00
+
+#define EM28XX_R24_VOFFSET 0x24 /* red balance */ /* signed */
+#define RED_BALANCE_DEFAULT 0x00
+
+#define EM28XX_R25_SHARPNESS 0x25 /* sharpness [0:4] */
+#define SHARPNESS_DEFAULT 0x00