super-white

[dcouzin]

My T42 has an SXGA+(1400x1050) TFT screen, with ATI Mobility Radeon 9600 series graphics card. When the cursor is white it is noticeably whiter than any other white on the screen. I can set a background color to 255-255-255 in a graphics program, and it is less bright than the cursor. What is the R-G-B of the cursor now? It looks like 400-400-400. How can the backlight have all that extra brightness, wasted over most of the screen? Is there any way to get that super-white for more than the cursor? When I tilt the screen (with the hinge) it darkens, but not the cursor -- contrast between cursor and screen increases greatly with this tilt -- as if the liquid crystal is fully transparent for the cursor. Why can't this occur over more of the LCD?

I've not looked at other LCDs, so am asking about this in the ThinkPad T4x forum.

[frdchang]

could be an optical illusion?

the cursor is lined by a black border that can affect how you perceive contrast.

[dcouzin]

I wondered about that too, but the fact that the relative brightness increases vastly when the screen is tilted shows that it's real.
Isn't yours, and everyone's, doing the same?

[Thinkpaddict]

I noticed that before in one of my Thinkpads, and I was initially as puzzled as you were, since after all nothing should be brighter than pure white.

I've come to the conclusion that there are a couple of possible explanations. The first one is what has been mentioned already (a visual effect.) The second possibility is that the pixels in the screen within the cursor are actually brighter than the rest of the screen's white pixels because they are a limited amount of pixels surrounded by an outline of black pixels, and this causes the pixels inside the white cursor to be actually brighter due to some (unknown to me) quirk of LCD technology.

[dcouzin]

Thank you for confirming that this happens. The black outline around the cursor is too thin -- occupies too little area -- to account for the super-white within the cursor. Also we don't get a super-white inside a letter "O"!
If you go to Mouse Properties>Pointers a Normal Select arrow is shown. Put the cursor next to this picture of the pointer and see the difference.
Apparently the graphics board knows when it has a cursor to make and and really puts a special voltage to those pixels.
For heaven's sake: the black cursor is super-black.

[dcouzin]

I think what's going on is this: The LCD is using reflective, rather than absorptive, polarizers. With reflective polarizers the light that doesn't emerge from the display is sent back to the backlight where it is mostly recaptured and redistributed. Thus there's little waste in having the 255-255-255 of the screen less bright than the cursor's 400-400-400 (or whatever). If all pixels were sent to 400-400-400, the whole screen would match the cursor, but then the whole screen would look as bright as it does now because the backlight would be dimmer (due to no return for recycling).
The graphics card has to "understand" the LCD so as to figure how much light is recycled at every moment (depending on what's displayed) and adjust the voltages to the pixels accordingly to keep what should have constant brightness constant.
It's quite fancy technology that lets the cursor be super-white without wasting light, and I'm surprised the LCD maker and graphics card maker haven't bragged about it.

[dr_st]

I still think it's nonsense and nothing but a mere optical effect. Post photos of a cursor over pure white background from different angles to prove me wrong (of course if you embed the photos in the post, edit the thread title to say *pics*, so that the slow connection users have a warning).

[dcouzin]

I made two photos to resolve dr_st's skepticism, but find that images can't be attached here. I sent them to his email address. Perhaps someone can offer a website to which to upload them to then be referenced.

It's a stunning phenomenon. Neither my LCD nor graphics card are special. Why aren't other ThinkPadders seeing it?

Note added: my 600X LCD doesn't do it.

[dr_st]

I've looked at the pictures, and it seems indeed amazingly strange. I'll eat my hat now...

I uploaded them to my Photobucket account, here are the links:

http://img.photobucket.com/albums/v65/d ... normal.jpg
http://img.photobucket.com/albums/v65/d ... tilted.jpg

[rkawakami]

Could it be possible that the video driver is altering the gamma, brightness and/or contrast for the mouse pointer(s)? I do not see a "super-bright" icon on my SXGA+ T23 but I can use the S3Gamma Plus utility to alter my screen (globally) to get a much brighter white than "normal".

[dcouzin]

That's it! I had long ago set my display to gamma=0.75; brightness=7; contrast=75 for appearance reasons, and the Radeon 9600 simply leaves cursors, of all sizes and shapes in all applications, at the default settings: 1, 0, 100.
This also explains why I found a black cursor extra black.
Probably other graphics boards treat cursors specially too.
(rkawakami's cursor might look darker than white when he gooses up the screen white.)
Thanks all for your patience in resolving the mystery.

[rkawakami]

Okay, so I was close . Instead of the gamma / brightness / contrast affecting only the cursor, it actually is the only thing that is not altered.

[dcouzin]

Ray,
You get a shiny cursor prize.
Dennis