How to adjust screen brightness (Fedora)
Hi guys,
This will sound like a stupid question, but I'm practically getting a tan off my screen. How does one adjust the brightness of the display in a laptop (Fujitsu Siemens Esprimo)running Fedora 8? I've tried using the 2-key function combination that works with various live CD distros no problem, yet on this (permanent) installation, any attempt to dim the (maximally bright) display reverts to maximum again within a fraction of a second. Can anyone assist? Thanks, CC. |
I think the command xgamma could help. Read the manpage I linked and try something like xgamma -gamma 0.5 in a terminal. Can't test it now, but I bet you will figure it out if the command doesn't work :)
Regards! |
I thought it would it quite easy.
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Right! Well, I entered your suggested command above in the terminal and it appeared to have been executed, because it echoed back something like (and i'm paraphrasing) was Red: 1, blue: 1, green: 1; now Red: 0.5, blue: 0.5, green: 0.5 indicating (to my simple mind at any rate)a halving of the total of white light, but it made absolutely no difference to the screen brightness. I didn't budget for the cost of welding goggles in my switchover to Linux, so... any other suggestions? tnx, CC. |
Completely,
The only problem with changing the gamma is that you are only stopping down the LCD, reducing the amount of light that passes from the CCFL (Cold Cathode Florescent Lamp). This reduces the number of colors, gray scales and range of luminance available to you. It is a lot like turning the contrast on yout television down. Furthermore, it does nothing to reduce the power used by the backlight thus providing no reduction in heat load, nor does it help your battery life, and it does not inrease your "green" karma. Most of the laptops I have worked with have (or can have) an entry in the /proc file system that allows the control of backlight brightness Here is an example from my system: ewaller@lappy ~ $ ls -l /proc/toshiba_smi total 0 -rw-rw-rw- 1 root root 0 Apr 5 08:25 aerial -rw-rw-rw- 1 root root 0 Apr 5 08:25 brightness -rw-rw-rw- 1 root root 0 Apr 5 08:25 display -rw-rw-rw- 1 root root 0 Apr 5 08:25 fn -rw-rw-rw- 1 root root 0 Apr 5 08:25 fn_f5 -rw-rw-rw- 1 root root 0 Apr 5 08:25 kill_switch ewaller@lappy ~ $ cat /proc/toshiba_smi/brightness brightness = 7 ewaller@lappy ~ $ echo 4 > /proc/toshiba_smi/brightness ewaller@lappy ~ $ cat /proc/toshiba_smi/brightness brightness = 4 This support can enabled in the kernel. The fact that it dims, and then reverts makes me think this may be enabled. Take a look in /proc and look for things like smi, Fujitsu, acpi. Drill down and see if you can find something related to brightness. If you do, use cat to look at the current value, and echo (see above) to try to change it. Good Luck e waller |
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Thanks for trying to help, though. CC. |
TFTs are great --most modern laptop displays are TFT. The TFT LCD has greater transmissivity of light because TFT structure provides a greater optical aperture -- but it is not self luminescent. TFT (Thin Film Transistor) LCD panels are still just programmable attenuators that require a backlight. Predominately, these backlights are CCFL, although LEDs are coming on strong. For now CCFLs hold the efficiency and cost edge.
The only technologies that I know of that do not require a backlight are LED matrix, Plasma, or OLED. The first two are power hungry and are not applicable to laptops, OLEDs are not quite ready for production. |
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Thanks for the lesson; I'll give it another shot and post back in due course! CC. |
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