camera looks slightly gamma brightened after using renderTexture

Running the following code one time appears to permanently make everything slightly whiter (except overlays), as if a gamma correction of about 2.2 were in play. The intent is to capture a Texture2D via renderTexture and then dispose of all other resources and set things back to normal. Any ideas why?

Code (CSharp):

1.        
2.     static Texture2D TakeScreenshot(int width, int height)
3.     {
4.         RenderTexture renderTexture = new RenderTexture(width, height, 24);
5.         Camera.main.targetTexture = renderTexture;
6.         Camera.main.Render();
7.         RenderTexture.active = renderTexture;
8.         Texture2D screenShot = new Texture2D(width, height, TextureFormat.RGB24, false);
9.         screenShot.ReadPixels(new Rect(0, 0, width, height), 0, 0);
10.         screenShot.Apply(false);
11.         Destroy(renderTexture);
12.         RenderTexture.active = null;
13.         Camera.main.targetTexture = null;
14.  
15.         return screenShot;
16.     }
17.  

(I know about UnityEngine.ScreenCapture, but I'm in Unity 5.6)