Which sentence determines that Robert is adjusting the brightness slider? Robert was editing a photograph. The highlighted portion of the picture and the middle tones became dark when he moved a slider to the extreme left. The luminance of the image turned to a middle gray when he moved a slider to the left. He increased the luminance of the pixels by pushing a slider to the extreme right. Because of this, important details of the picture were lost. However, sometimes Auto Tone or Auto Contrast can help resolve tonal problems.