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LCD backlight switch

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Offline fudgey

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LCD backlight switch
« on: 06 / February / 2008, 16:43:49 »
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I have no idea if this is at all possible, but I wish the LCD backlight could be shut down without shutting down the LCD.

A lot of power could be saved during motion detection which (if I'm not mistaken) requires the display to be enabled constantly.
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Offline GrAnd

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Re: LCD backlight switch
« Reply #1 on: 06 / February / 2008, 16:57:18 »
Quote from: fudgey on 06 / February / 2008, 16:43:49
A lot of power could be saved during motion detection which (if I'm not mistaken) requires the display to be enabled constantly.
MD requires the shutter to be opened and the camera to be read the data from sensor. So, we have to find a function to switch the LCD off without closing the shutter. (Because originally any camera closes the shutter when the LCD is off by pressing disp button or by energy saving. Except the S-series due to having the EVF.)
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Offline Barney Fife

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Re: LCD backlight switch
« Reply #2 on: 06 / February / 2008, 18:04:56 »
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« Last Edit: 22 / April / 2008, 11:02:51 by Barney Fife »
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Offline PhyrePhoX

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Re: LCD backlight switch
« Reply #3 on: 06 / February / 2008, 18:28:04 »
that'd be grand! (no pun intended!)
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Offline fingalo

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Re: LCD backlight switch
« Reply #4 on: 06 / February / 2008, 18:31:23 »
Oh, I think Ewavr has made backlight contol in his own 710 build. I tested that on the S3 and it is possible to control the PWM that control the backlight of the LCD.
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Offline fudgey

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Re: LCD backlight switch
« Reply #5 on: 07 / February / 2008, 10:28:46 »
Oh, a configurable backlight dimmer would be phenomenally useful not only for scripts but also for all everyday shooting :o. It's not always bright daylight and my camera screen is almost too bright to look at when it's dark and it feels bad to see the battery drain for nothing. In moderate lighting, many LCD's are quite readable even without backlight.

For motion detector power saving, disabling the entire display would be useful as well, of course.
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Offline Jucifer

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Re: LCD backlight switch
« Reply #6 on: 07 / February / 2008, 11:41:31 »
Would also be very useful for power saving when shooting time lapses (can't (easily?) MF when display off).
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Offline Barney Fife

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Re: LCD backlight switch
« Reply #7 on: 07 / February / 2008, 12:25:29 »
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« Last Edit: 22 / April / 2008, 11:03:11 by Barney Fife »
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[acseven/admin commented out: please refrain from more direct offensive language to any user. FW complaints to me] I felt it imperative to withdraw my TOTAL participation. Nobody has my permission, nor the right, to reinstate MY posts. Make-do with my quoted text in others' replies only. Bye
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Offline fudgey

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Re: LCD backlight switch
« Reply #8 on: 07 / February / 2008, 12:49:14 »
Ah, the camera acting as a light bulb in the dark problem :D

Well, if I understood fingalo's post correctly, at least the A710 and S3 have PWM controlled backlight... that generally means it's adjustable, doesn't it?

And if we can have a menu item and/or ubasic command to set a value for dimming, we can certainly somehow have CHDK approximate the amount ambient light (this is a camera after all, it's was made to do that) and adjust it automatically for power saving if desired. 8) It's quite possible that not all models have control over backlight power, of course.
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Offline ewavr

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Re: LCD backlight switch
« Reply #9 on: 07 / February / 2008, 16:27:33 »
Well, I inspected some cameras firmware in IDA (digic2 and digic3). All of them have PWM controlled LED backlight. PWM controller have 2 channels, S-series uses both (for EVF/LCD ?), other cameras - only second.
This controller can be programmed using firmware functions (SetValSdpwmCh0 and SetValSdpwmCh1) or direct I/O port writing (0xC0910004 and 0xC0910080, only low 16 bit is significant). After display mode change (for example play/record switch) firmware restores LED brightness, saved in some memory locations.
For example, A710:

ROM:FFD38F28                 STR     LR, [SP,#-4]!   
ROM:FFD38F2C                 LDR     R3, =0x702F0
ROM:FFD38F30                 LDRH    R0, [R3]       
ROM:FFD38F34                 LDR     LR, [SP],#4   
ROM:FFD38F38                 B       SetValSdpwmCh1

Warning: Operations with LED brightness are potentially dangerous and can damage backlight of LCD!

edit: These I/O ports also can be read.
« Last Edit: 07 / February / 2008, 16:54:32 by ewavr »
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