Finding a neutral midtone while color correcting has always been kind of tricky. Well, it was until Dave Cross, who works with me as Senior Developer, Education and Curriculum for the National Association of Photoshop Professionals (NAPP), came into my office one day to show me his amazing trick for finding right where the midtones live in just about any image. When he showed me, I immediately blacked out. After I came to, I begged Dave to let me share his very slick trick in my book, and being the friendly Canadian he is, he obliged.
Open any color photo, and click on the Create a New Layer icon at the bottom of the Layers panel to create a new blank layer. Then, go under the Edit menu and choose Fill. When the Fill dialog appears, in the Contents section, under the Use pop-up menu, choose 50% Gray (as shown here).
When you click OK, it fills your layer with (you guessed it) 50% gray (you can see the gray thumbnail for Layer 1 in the Layers panel shown here). Now, go to the Layers panel and change the blend mode of this layer to Difference. Changing the layer blend mode to Differ-ence doesn’t do much for the look of your photo (as you can see here), but don’t worry—it’s only temporary.
Choose Threshold from the Create New Adjustment Layer pop-up menu at the bottom of the Layers panel. Then, in the Adjustments panel, drag the slider under the histogram all the way to the left (your photo will turn completely white). Now, slowly drag the slider back to the right, and the first areas that appear in black are the neutral midtones. In the bottom right of this photo is a decent-sized area of black, so that will be our midtone correction point. To help you remember exactly where that area is, get the Color Sampler tool (nested under the Eye-dropper tool), and click on that spot to add a Color Sampler point as a reminder. Then click the Trash icon at the bottom of the Adjustments panel to discard the adjustment layer.
Now that your midtone point is marked, go back to the Layers panel and drag the 50% gray layer onto the Trash icon to delete it (it already did its job, so you can get rid of it). You’ll see your full-color photo again. Now, click on the Curves icon in the Adjustments panel (the second icon from the right in the top row) to open the Curves Adjustments panel, get the midtones Eyedropper (it’s the middle Eyedropper), and click directly on that Color Sampler point (shown circled in red here).
That’s it; you’ve found the neutral midtones and corrected any color cast within them. So, will this trick work every time? It works most of the time, but you will run across photos that just don’t have a neutral midtone, so you’ll have to either not correct the midtones or go back to what we used to do—guess.