That Color Cast…Be Gone! - How to Remove Color Cast from Images

While this technique is still valid, it's the method used back in the days of Photoshop CS/CS2 and was written 06.2004. Since the introduction of Capture NX, I've do all my color cast removal there, working with a Raw file. If you're using CS3, I highly recommend you search the web for Super Curves, a faster and better method than this for color cast removal.

What makes a photo taken in the early morning hours or late hours of the day special? What is it about sunsets that make landscapes come alive? It’s the color cast this light brings to the scene. The warm light changes the entire feel and emotional response to the scene. This is a good color cast. It’s a color cast we not only desire but go to great lengths to capture. Smog, this can create a nasty color cast. Overcast skies, predawn light, rain and snow, the light during these times is extremely blue and creates another color cast that could be completely undesirable in your photograph. Then there is a color cast that your mind filters out, but the camera doesn’t because there is a deficiency in your capture device. Depending on how YOU want to communicate the scene, since you’re the only one who was there when the photograph was taken and you know what YOU want to communicate, determines whether the color cast is a good thing or a bad thing. There are NO set rules!

Before and After

Now you will most definitely hear differing opinions on this matter. That’s the very nature of art and photography. Whether or not color casts are good or bad and how to remove them is a big debate with some. I can’t emphasize enough that it’s YOUR photograph, YOUR vision and there truly is no right or wrong. You’ve got to make the call. You can easily see the magic and be sucked into it. You could apply this technique perfectly and you might not see any change. This is all part of the learning process. There are many, many ways of removing a color cast in the digital darkroom. The only way you know when to use this technique and when not to is by experimenting and seeing for yourself what works and what doesn’t work. You should know that using the technique we’re about to delve into is what most photographers use to have consistent output. In other words, if you want consistent results in your prints, then this is a technique you want to use on every image even though it might make no visible change. Many will argue this is a must. Just keep in mind what I said in the beginning, only YOU know what you saw, what you photographed and most importantly, what YOU want to communicate. I keep saying that what the world doesn’t need is another technically perfect photograph.

To begin with, our goal state is to be working in a calibrated world. We’re going to be making decisions on color based on what we’re seeing on the monitor. We’re either going to leave or remove a color cast based on what we SEE. If we’re not working on a calibrated monitor, we can make decisions that we’ll regret when that print comes rolling out of the printer. With that understood, let’s set up our digital darkroom.

Setup This technique requires some precise measurements and sample taking. For that reason, I first set my cursor to Precise. To do that, go to Edit > Preferences > Display & Cursors and under Other Cursors select Precise. Next you should check your sample point. You do that by selecting the Eyedropper / Color Sampler tool (tap I) and look at the box in the tool bar. You have three options and since we’re dealing with high res files, I would recommend 3 by 3 Average. I personally don’t want to set the color for the whole file based on one pixel. Next, I drag out my Info Pallet. I leave it as a stand alone pallet. I leave my cursor to Precise all the time, but do I use this technique on every photograph? I most certainly do not. I make the judgment call on that when I take the photograph. I know when I take the photo if I’ve got a color cast I have to remove or not. So with PhotoShop set up, let’s remove a color cast.

With the file open, the first thing I do is tap the F key. This changes the desktop to Fullscreen Mode. This places the photograph on a neutral gray background, which is better for your eyes in matching colors. It also makes available some other keyboard shortcuts we’ll talk about and use a lot. Looking at this photo of the Bald Eagle, you probably don’t see anything out of the ordinary.

But knowing the light on this Bald Eagle was being filtered through steam, there’s a bad color cast that needs to be removed. Keep in mind that I have three criteria going through my mind when I’m in the digital darkroom. I want to create only quality, build flexibility into everything and do it FAST! With that in mind, you need to keep one more thing in mind as well. We never, ever want to affect a permanent change to our file. So one of the main tools we’re going to take advantage of are Adjustment Layers. Adj Layers are our friend as you’ll soon see. For this reason, my Layers Pallet is always open because I go back and forth to it all the time. Here are the steps to remove that cast.

Step 1:
Click on the Zen Icon at the bottom of the Layer Pallet, Create Adj Layer button. Click on it and then click on Threshold. Threshold breaks our image into just Black and White. This is not a permanent change. We’re going to use Threshold only to find our Black and White point in the photograph. We’re going to move the slider on Threshold all the way to the left to find our black point first. We’re going to zoom into these areas still appearing as black dots by PS Info Palette depressing Ctrl (Cmd on Mac) and then the Space Bar. This gives us the Magnify Tool, which we can use to enlarge the area with the remaining black. We can also click on the Preview box in the Threshold to see exactly what those black dots are in our photograph.

Step 2:
Finding the Black Point and White point requires some technical input as well as aesthetical input IMHO. Let’s start with the Black Point since that’s You want to click on Create Adj Layer Button and then click on Threshold. That will bring your image to this B&W state. This also bring up the Threshold dialog box Info Palette is essential! 13 normally the easiest to find. Using the remaining black pixels, move your sample point around while looking at the Info Palette, at the RGB info. As you move it around you’ll more than likely see the values askew, as in all the numbers are not the same as 1/1/1. Numbers for example like 1/5/2 indicates a color cast. I tend to look for the sample point with the biggest variance in the RGB values. Now here’s the trickiest part, placing a sample point. While holding down the SHIFT key, click on the sample point where you found that color cast White Point variance. When done correctly, you’ll see a crosshairs with the number 1. That’s your Black Point.

Step 3:
This is basically the same as step 2, but with an important twist. Finding and setting your White Point is done in the same fashion. You move the Threshold slider to the right. We’re dealing with highlights here so you must take care in selecting your White Point. In theory, you want to select the brightest white because PS is going to push all other white to that point. If you don’t select the brightest, you will Select White Point lose highlight detail! Now that might not be important in your photograph but then again, it might be so you need to be aware of that. In this example of the Bald Eagle, I stopped the slider at 191 and then looked at my sample point RGB reading. I selected a point on the head that read 191 / 156 / 46. Man, is there a color cast! With that done, I close Threshold by clicking on Cancel. If you make the mistake and click on OK, you can undo by Ctrl (Cmd) Z or simply drag the layer to the trash. Holding down the Shift key and clicking is how you create your sample point. Depressing and holding down the Space Bar and the Ctrl (Cmd) keys calls up the Magnifier so you can quickly zoom in on the White Pixels can either simply drag the Threshold Layer in the Layer pallet to the trash or type Ctrl (Cmd) Z. You should now be viewing your photograph in full color. You can use Ctrl (Cmd) 0 to zoom back out. NOTE: the sampe points you just created do not print but if they bother you, you can either drag them off using the eyedropper or hide them with Ctrl (Cmd) H.

Step 4:
We now want to put to use those color sampler points. We’re going to do that by using a Curves Adj Layer. Click on the Zen icon, Create Adj Layer and click on Curves. We’re going to use the Black & White Point Eyedroppers starting with the Black Point Eyedropper first.

Curves Adjusment Layer

Click on the BPE and move your cursor so it’s over the Black Point sample point you created with Threshold, #1 and click. In the case of the Bald Eagle, we saw no real change. That’s because our sample point was 0 / 1 / 0. If you want to have perfect digital darkroom habits, you would now click OK and rename this layer as Black Point. You then would create another Curves Adj Layer for the White Point. Or, you can just click on the White Point Eyedropper and make both corrections in the one layer. Take the WPE and click on the White sample point #2. When we do that with the Bald Eagle, there is a dramatic difference. That’s because our White Point was 191 / 156 / 46, lots of contamination.

Step 5:
Once you’ve done this, you’ll see you’ve created 1(2) layers that you should name Color Cast. With that, your image has its color cast removed and you can move on to work the image as you desire. This simple technique can make a huge impact on your visual communication!

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