Occasional screen shadows iPhone 5S
Great picture. I'm not sure I would be able to answer from the words alone.

If you focus on two areas - just above the words Airdrop - the fading/smearing looks quite evident.


the speaker icon for mute/low volume has definite "smearing"
the >> fast forward black triangles also exhibit "smearing"


I don't know the technical term for that bleed, but it's a hardware issue with the voltage controlling the LCD panel. Either the chip that drives the graphics is failing or the connections between the circuits embedded in the LCD and the controlling chip. Basically, reseating the LVDS cable would be the first things I would try if I were a repair technician and needing to fix a phone with that display.

To check your phone against other phones and devices, this web page is fabulous for test patterns:


http://www.lagom.nl/lcd-test/all_tests.php


You'll want the detailed pages for how to use them, but the link above is my gold standard for just looking at two screens side by side to get a quick check of the LCD calibration and performance.

Without opening the hardware and inspecting things, here are questions I'd ask before getting a repair:


Has the phone been dropped recently or had a large shock (even in case, a drop can cause internal damage)?
Is there warranty or AppleCare coverage? (If so - seek repair before it expires)
Has the phone been opened by Apple or anyone else recently (or ever?)?