I am shooting in manual mode on my Canon G7X Mark II. I am using a studio light box that has natural lighting, white backdrop, and the reflecting sides. I use this for taking pictures of my bakery items (cakes, cupcakes, cookies, etc). My issue is that the whites are coming out grey, even though I see white. I've adjusted Shutter, Aperature, and ISO but the image is either over exposed or grey. I read that this happens because the camera is set up to add 18% grey. It was recommended to increase exposure by 1 stop, so I turn the dial up to +1, but nothing changes. When I move the camera around to different areas, the exposure is constantly changing on it's own. Is the Exposure dial not available in manual mode?