The root cause of this issue is that the colors are not getting rendered properly on AMOLED screen. Here's quick solution how can you fix the problem.
Solution to Galaxy S4 Smearing IssueThe said problem is prominent on black background with gray text so we will be making some changes in your RGB values. We can fix the issue if we override the default RGV values. You will have to download app 'screen adjuster ' from Google play. This app helps in adjusting defaults values of your screen.
Steps to follow:
1. Install 'Screen Adjuster' app from Play store.
2. Go to options and change the contrast level from -0 to -10 (you can go upto -20 depending on how far your eyes can balance between smearing and pitch black)
3. Turn on the adjuster.
There is a small problem in using the app is that it disables the 'Install' button when it is running so whenever you want to install new apps, you will have to disable the screen adjuster and install the app. Enable screen adjuster again when you are done. For now this is the temporary solution that has been discovered, and hopefully Samsung releases a patch to fix this problem. Have you encountered this issue? Do you know of any other methods to solve this? Let us know in the comments.