Image Map Image Map
Results 1 to 9 of 9

Thread: Might be a CRT monitor glare issue

  1. #1

    Default Might be a CRT monitor glare issue

    I notice on my crt monitors that whenever I'm on a blank black screen with gray windows around it, for example in MS paint, there is a grayish white shadow outline against it. Also the mouse pointer leaves a shadowy trail. I have not changed any mouse settings. Is this damage to the antiglare coating? The monitors surface looks good and shiny when the monitor is turned off. My monitors each have a varying degree of this shadow. I use 70% rubbing alcohol to remove fingerprints from my monitors. I wonder if that contributed to it. I wonder if it's fixable so the screen is less reflective. I have never seen a brand new crt before, so I have no real comparison.

    Also I'm not believing people when they say black on a crt looks like real black. Black looks dark dark gray to me. In my experience LCDs are better at showing black. I dunno, maybe it's related to the light/dark shadow I mention. Like I said, I have never seen a brand new crt.

  2. #2
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    28,871
    Blog Entries
    20

    Default

    It depends on how you have your CRT adjusted. Bumping up the contrast may help, if this annoys you. On one of my NEC LCD monitors, there's actually a control for grayscale rendering. It wasn't until I came across some "invisble" (gray on black) text that I realized the control even existed (RTFM).

    But if you want true black, get an OLED monitor; bring plenty of bux.

  3. #3
    Join Date
    Jan 2014
    Location
    Freedom City
    Posts
    6,249
    Blog Entries
    2

    Default

    And savor it whilst it's still black. Every OLED display I've seen has burn-in. Of course, most plasma displays I've seen are worse.

  4. #4
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    28,871
    Blog Entries
    20

    Default

    Yeah, well, it's still in the development stage (i.e. let's test it on the customer). There's also QLED and, on the horizon, MicroLED. All depends on your patience and bank account.

  5. #5

    Default

    I cannot think how the surface reflectivity of the CRT's screen could account for anything you have noticed, most likely it would alter reflections from other light sources in the room from the CRT face, not alter light generated by the CRT phosphors. CRT phosphors have persistence and to some extent our own vision, so a trailing tail is not uncommon seen behind an image like a mouse pointer.

    The other effect you are talking about with the shadow outline: It depends on how wide this is to be able to diagnose it (please attach a photo) There are a couple of possibilities. If this is just on the horizontal axis, it could represent a form of ringing or overshoot in the CRT drive on abrupt signal level transitions (in other words a lack of perfect square wave response in the video signal circuits). In some sets this aspect of the video frequency response was called "Aperture Correction" and there was a control for it. Other times with poor video cable terminations and reflected signals can be seen too.

    You are right, there is often no such thing as a true black from a CRT. This is because, in the white regions where high energy electrons strike the screen, there is secondary emission of some of them and they end up on the adjacent phosphor areas causing a subtle flare or glow next to the illuminated areas. But usually, if the contrast and brightness controls are set properly, the effect is too small to be of any concern.

  6. #6

    Default

    It's not screen burn-in. I'll take some pictures when I have the time.

  7. #7
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    28,871
    Blog Entries
    20

    Default

    One way to improve the contrast of a display was to put a dark cloth mesh over the tube face--it tends to reduce reflections and gives a better image. One of the common DIY dodges was to take a pair of dark-colored women's nylon stockings and stretch one over the CRT face. You only need one--the other one can be used for bank robberies.

    3M also made a shaped-to-fit polarizing filter for common CRTs, but I haven't seen one in many years. But Hugo's right--some electronics manage to stray and detract from a true black.

  8. #8

    Default

    Quote Originally Posted by Chuck(G) View Post
    3M also made a shaped-to-fit polarizing filter for common CRTs, but I haven't seen one in many years.
    I have a NIB, NOS Fellowes Anti-Glare Filter if that's of interest. It's a polarizer.
    ☀☀☀ Visit Take Another Step for both computer and non-computer related discussions. ☀☀☀

    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen

  9. #9
    Join Date
    Jan 2013
    Location
    Marietta, GA
    Posts
    2,798

    Default

    Quote Originally Posted by computerdude92 View Post
    Also I'm not believing people when they say black on a crt looks like real black. Black looks dark dark gray to me. In my experience LCDs are better at showing black. I dunno, maybe it's related to the light/dark shadow I mention. Like I said, I have never seen a brand new crt.
    The idea is that in a completely darkened room a completely black CRT screen should emit no light (except perhaps a small amount out of the back from the filament) In the 1990s this is how one would play games like DOOM, and it isn't the same on crappy modern LCD monitors that always display backlit gray instead of true black.

    This does depend on the CRT monitor being set right, otherwise they can display a dimly glowing "raster" in the background instead of blackness. This is possible because it makes some kind of images easier to read.

    On some very early monitors the brightness/contrast may change slightly when certain kinds of images are displayed on the screen - such as a window surrounding a black area, or when the monitor changes resolutions.

    In lit environments you will, of course, see that the physical surface of the CRT is actually grey. Some earlier CRTs are much lighter in color. Typically, darker looking CRTs have a layer of anti-glare.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •