Because the center of sunspots is significantly cooler than the surroundings, it usually is shown as esssentially black in images. I prefer to leave the centers more at their natural luminosity where they can show whatever interior structure exists. To me it seems that the interiors contain the same kind of convection cells as the surrounding surface just cooler and, therefore, appear darker. Using my QHY290MM camera, video frames show no clipped black or white pixels. In other words there isn't as much contrast as one might expect on the surface of the sun between surrounding cells and the interior of sunspots.