As mentioned, try putting a light to the side and letting it flow over the sandwich instead of light coming down from above. I have a black light which was suppose to help see white on white stitching; but it does not do the job. When I need to stitch on busy fabrics doing free motion, I clamp a "trouble light" on the side of my Gammill frame and let the light "wash" over the sandwich which shows me the indention of where I have quilted.