How White Balance Affects Exposure

But wait, I shoot raw so my white balance doesn’t matter right!? Well, you would technically be incorrect, and in this article I will explain why. Now up until recently, I’ve always left my white balance on Auto, and because I shot in RAW, I knew if it was off I could just fix it in post. That is part of the beauty of shooting in RAW. Well, this has all changed for me.

I’ve noticed on occasion as I was photographing sunrises and sunsets in Arizona, that when the sky would turn to that crazy fire in red, orange and yellow, and those glorious high altitude clouds would catch every bit of that color, my camera’s white balance would make the image extremely blue to compensate. Now I just thought it was no big deal, that I would just fix it in post. But then I started taking note of the histogram. So I decided to take my white balance from Auto to Kelvin.

It was then that I noticed something when I started adjusting the color temperature on the back of the screen. My histogram would move with the change in White balance! Now this was a revelation to me. It hadn’t occurred to me that colors have luminosity values. Yep, that’s right. Now that may seem obvious, but to me I had never really thought of it affecting my exposure.

So how does this affect the way we expose an image? I’m glad you asked! You see, our goal is to gather as much data, or light, onto our camera’s sensor as possible without overexposing the highlights. This technique is known as, “Expose to the Right.” So what we need to do with our white balance is get it as neutral as possible. Simply adjust the white balance to mimic exactly what you see with your eyes. This will give you the most accurate histogram possible.

Now let’s use the example I mentioned earlier. The sun is setting, and that sky just goes crazy with reds, yellows and oranges. Now the cameras Auto White Balance sees all of these warm colors, and then tries to balance it by pushing the temperature towards blue. Now you expose to the right, just short of over exposing the highlights. Now you go home, jump on the computer, and import the photo into Lightroom. Your highlights are just short of clipping, so you’re ok there. But, the image is very blue due to the white balance, so you need to warm it up a bit. Here is where you run into a potential problem. Bringing in the warmer tones, with higher luminosity values, you run the risk of blowing out those highlights because you don’t have the latitude in the exposure due to the original white balance. You would have to drop exposure, maybe add a gradient filter, raise shadows and probably a few other things just try and compensate for that white balance being too blue. On top of that potential issue, when you warm up the white balance, you remove some of the intensity and natural saturation from the cooler tones. Conversely, when you cool down the white balance, you remove some of the natural saturation from the warmer colors.

There are always things you can do in post to fix issues. Double processing, exposure bracketing, or using the various filters in post processing to adjust the tones in the image. But I’m a big fan of making things as easy as possible once I get on the computer. It’s very easy to fall into the habit of ‘I’ll fix it in post’ mentality. So give this a try, make that white balance as close to what you see as possible, completely neutral, and gather as much light as possible on your sensor. You will get the best RAW file possible to work with and really be able to let that creativity flow! If you are interested, I have a video on my YouTube channel that goes over this in detail. Be sure to check it out and leave a comment and let me know what you think!