The (Not So?) Dummies Guide to Taking Pictures of Your Backlight Bleed
(sorry videos and pics are so dark, view them in the dark I guess)
So check out this interesting video I just took of my monitor while using a polarized lens on my Sony NEX5:
Assuming the LCD panel is letting through vertically polarized light (up-down waves), which is just a guess, then when the lens filter is rotated to only let through horizontal light, ZERO light gets through and it appears black. Viewing the panel up close with the filter trying to block all light, what do you notice? It can't block the corner light as it's actually at a different phase. Only when I step farther away from the screen am I able to see that all light hitting my camera is at the same phase (approximately of course). This greater distance from the screen is the correct test scenario for checking for backlight bleed if you're only going to take a single picture.
So, a lot of backlight bleed isn't what we're talking about on here when we say "my monitor has really bad backlight bleed". Some of the light comes through even though we don't want it to, but only when viewed at angles
. This is standard and unavoidable for LCD panels universally. Light coming straight out of the screen should
all be at the same phase angle (think of an up-down wave or a left-right wave as examples of waves of light at different phases). This is because light of any other phase is blocked by the polarization filter in the screen. When viewing the screen from an angle (which is what you're doing when you're up close and looking around the edge of the screen), you can see light of a different phase (and more of it) passing through the LCD panel. This is what gives LCDs that annoying "shimmer" as you move your head around while looking at an LCD. Unless you have a plasma screen, CRT, or OLED panel for a computer monitor, just get used to it. So, you're not looking for backlight bleed (this out of phase light coming to your eye at an angle) from places you're viewing at an angle, you're looking for it from areas directly in front of your eye/camera.
So, below are some pictures to show the effect in action, but the rule is:SHOOT FROM FAR AWAY, OR TAKE ENOUGH SHOTS TO SHOW EACH CORNER OR TROUBLE AREA CENTERED DEAD-ON TO THE CAMERAThe effect shooting angle has on the exact same corner of my monitor: (Click to show)
Each of the corners of my monitor when shot straight at each: (Click to show)
The effect of screen distance on false backlight bleed: (Click to show)
Shot up close at 19mm (APS-C sensor size)
Shot far away at 55mm (APS-C sensor size)
I don't have a great separate picture for this, but due to the R/G/B sub-pixel arrangement (I believe), you're going to see red or yellow colors from out of phase light from the right of the screen and blue or green light from the left side of the screen (unless you're somehow hanging from the ceiling or have mounted your monitor upside-down). As you can see from the pictures of my monitor, mine appears to have that nasty yellow bleed from the top right, but it's really only the standard out-of-phase light from corners, and is on the right side of the screen. It goes away once you view it straight-on.
I know this is a large post, but last thing, I promise...
Pinching of the screen or other issues that cause the "real" backlight bleed usually still use the effect described above to discolor the screen or add extra light, but it's visible even when viewed straight-on. That's the difference.
How to show real backlight bleed with a video (kinda crappy video though):