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Contrast/brightness controls on active matrix LCDs?

Older ThinkPads.. from the 600, the 7xx, the iSeries, 300, 500, the Transnote and, of course, the 701
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goldeneagle
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Contrast/brightness controls on active matrix LCDs?

#1 Post by goldeneagle » Thu Sep 07, 2017 9:02 pm

Howdy y'all. I've picked up some ThinkPads here and there on ebay, and noticed some of them (all TFT) have the brightness and contrast controls on the right. I'm wondering if anyone knows if this was normal from the factory? I've seen about 4 or 5 machines so far that have both sliders, that are NOT DSTN models, and don't look like they've ever been disassembled.
Historic ThinkPads owned:
300, 360C, 360CE (x2), 360CSE, 510CS, 560, 560E, 701C, 701CS, 730TE, 750, 750C, 755C (x3), 755CE, 755CX (SVGA), 755CDV, 760ED, 770
Newer ThinkPads owned:
T520, W520 (x2), X220 Tablet (x4), and some T61/X61T laying around somewhere

Thinkpad4by3
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Re: Contrast/brightness controls on active matrix LCDs?

#2 Post by Thinkpad4by3 » Fri Sep 08, 2017 9:59 am

My 755C has the same thing with both contrast and brightness controls. All I can assume is that the machines were serviced and that what was on hand.
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The efficiency of two screens equally sized with equal numbers if pixels are equal. The time spent by a 4:3 user complaining about 16:9 is proportional to the inefficiency working with a 16:9 display, therefore the amount of useful work extracted is equal.

fultontech
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Re: Contrast/brightness controls on active matrix LCDs?

#3 Post by fultontech » Fri Sep 08, 2017 10:05 am

I'd have to look, but I recall the User's Guide for the 750C stating it was one way for TFT and another for Monochrome, etc. I noticed later production display units didn't seem to follow that convention.
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IBM ThinkPad 700, 720C, 750Cs, 360C, 360P, 360CE, 360PE, 730TE, PC110, 365CSD, 365ED, 701Cs, 820, 600X, 770X, 240, T30
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goldeneagle
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Re: Contrast/brightness controls on active matrix LCDs?

#4 Post by goldeneagle » Fri Sep 08, 2017 10:29 am

What's also weird is that I noticed an image of a TFT machine having both controls in the ThinkPad Demo last night (couldn't figure out a better way at the moment to drain a newly rebuilt battery). Also, the HMM does reference a TFT without contrast control, but the one above it doesn't say anything (which I assume means there was that option).

I also have this same feature on a 750C I very acquired a week ago (seller advertised the listing as 2 x 755C, which I'd bought for batteries and HDD caddies, but got lucky with 1 system being a 750C and the 755C having a 32MB IC DRAM inside).
Historic ThinkPads owned:
300, 360C, 360CE (x2), 360CSE, 510CS, 560, 560E, 701C, 701CS, 730TE, 750, 750C, 755C (x3), 755CE, 755CX (SVGA), 755CDV, 760ED, 770
Newer ThinkPads owned:
T520, W520 (x2), X220 Tablet (x4), and some T61/X61T laying around somewhere

goldeneagle
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Posts: 107
Joined: Sat May 31, 2014 8:06 pm
Location: Bandera, TX

Re: Contrast/brightness controls on active matrix LCDs?

#5 Post by goldeneagle » Mon Sep 11, 2017 3:34 pm

And... I answered my own question after disassembling the LCD assembly, because the sliders weren't working. Looks like this is actually a factory option at some point, and not just a part swapped with a DSTN screen. Pretty odd, since you don't otherwise see contrast on TFT screens...
Historic ThinkPads owned:
300, 360C, 360CE (x2), 360CSE, 510CS, 560, 560E, 701C, 701CS, 730TE, 750, 750C, 755C (x3), 755CE, 755CX (SVGA), 755CDV, 760ED, 770
Newer ThinkPads owned:
T520, W520 (x2), X220 Tablet (x4), and some T61/X61T laying around somewhere

Thinkpad4by3
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Joined: Sun Aug 09, 2015 9:25 am
Location: N. Bellmore, ny

Re: Contrast/brightness controls on active matrix LCDs?

#6 Post by Thinkpad4by3 » Mon Sep 11, 2017 3:39 pm

I find it convenient for DOS prompts. Allows the colors more vivid when in 4/16 color mode.
Thinkpad4by3's Law of the Universe.

The efficiency of two screens equally sized with equal numbers if pixels are equal. The time spent by a 4:3 user complaining about 16:9 is proportional to the inefficiency working with a 16:9 display, therefore the amount of useful work extracted is equal.

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