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Just a suggestion, and this would give some credibility to your efforts...

Field test this! And field test it over several different nights (don't wait for a star party... that is a bad place to test and experiment ).

I think a good test for this would be to take it to a couple of dark observing sites that are in regular use and get some (say 3 or more) experienced visual observers (not imagers) to look at it later in the evening (say around midnight) and then get their opinion as to how well it works. I have found that most of my red light tests at home aren't sufficient because I can't get that effect of 2 hour dark adapted eyes at a dark site. This would be a good acid test.

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Yeah, excellent suggestion. I'd do that, if it weren't for a couple of issues.. mainly, that I'm a 2 hour drive from a decent dark site, and I'm in england and even if I went there it would be cloudy

I agree though - as soon as it's possible, I'll be field testing this (and my imaging application, which I wrote this for). In the mean time, the best I can do is test it in a dark room (I tend to work really late at night, so that's not such an issue). And hope other people give me some feedback on what's right / wrong with it too

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Another way to test (that should be done in addition to, not instead of) is to get a laptop with a red plexiglass screen on it and dimmed down to what would be considered acceptable and make some side by side comparisons, both subjectively (with experienced visual observers) and with a light meter at a benchmark distance. Again, do this around midnight. This is similar to a method we used to benchmark acceptable light levels at Texas Star Party.

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I'll see if I can get hold of some plexiglass and a light meter. I can say though, at least with the LED screen, it's more than dark enough. In my tests above, I was in a pitch black room and could barely see well enough to use the computer. There's minimal light leakage. If plexiglass performs better, it'll be too dark to use

With a traditional backlight, it might be worse. My own laptop (this one is one I borrowed at work) is an old powerbook, so that will be a good test.

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I don't mean to sound like a skeptic about all of this (I appreciate and respect the effort you have put into this problem). But I think if you can establish some measurable or well founded benchmarks, it could go a long way to establishing this as an alternative method, at least for folks with MacBooks.

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This has been an increasing problem at star parties, especially the larger ones, simply because modern laptop displays are brighter and they (out of the box) cannot be dimmed sufficiently low enough to not be an adverse light and still be usable. And even then, the so-called "night vision" mode utilized in most application on these computers has been inconsistent, with things like system dialogs popping up in full color mode (with lots of white). The only practical solution has been to use dark red filtering overlays.

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Most applications with a 'night mode' only make the application red. I agree, this isn't anywhere near good enough. In my application, I don't do that - I tell the video card to effectively turn off green + blue, so it's impossible to get something like a popup in normal colour.

The exception is applications that restore the video card settings. The only thing that does that I've seen so far is the screensaver - and I can turn that red, after a brief flicker of white. I've included controls to disable / replace the screensaver to get rid of that issue. Perhaps more will turn up, we'll see

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I hope your solution can pass these tests. It could be an acceptable solution if it can and would have the weight of outside opinions and measures.

P.S. Now I can certainly try this on my MacBook... Can you write a similar solution for Windows???

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There is really no reason an LED backlit display can't be made to be extremely dim (particularly if the panel controls LED brightness via PWM - it can be any brightness they want then). That probably isn't the case on CCFL backlit displays.

BTW, I'm unsurprised that this worked on the macbook - you may have noticed that they charge more. There is a reason for this - they tend to use higher quality components. (No flames intended - they DO charge for this stuff.)

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It's not quite that simple.. or that complex either On the macs I've tried, the laptops have all gone very dark (LED or CCFL). On the desktops, they don't go very dark at all (LED or CCFL). I think it's just a case of what the firmware is set to allow. Perhaps it's possible to control the hardware directly for a better range even?

What I can say though is that there's way less backlight leakage with LED, and that makes quite a difference.

You're right, they do charge more - compare a mac with a similarly specced PC and they're actually pretty cheap really, but most PCs aren't so well specced so they look expensive

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On the PC, it's possible to control the brightness in several ways:
1. You can directly manipulate the DDC /EDID. (Actually you could to this on the mac too). You can tell the monitor to dim itself - you just don't have control over the range. The details of accessing the DDC are somewhat intertwined with the video card, however.
2. There are IOCTLS (in XP) and a WDDM interface (Vista / Win7) for monitor brightness control.

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It's not quite that simple.. or that complex either On the macs I've tried, the laptops have all gone very dark (LED or CCFL). On the desktops, they don't go very dark at all (LED or CCFL). I think it's just a case of what the firmware is set to allow. Perhaps it's possible to control the hardware directly for a better range even?

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What I can say though is that there's way less backlight leakage with LED, and that makes quite a difference.

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Yes, I would expect that. That's one of the things I'd noticed with my monitor in my observatory. I can actually make it quite dim, and I can control the gamma on my video card, killing blue and green entirely. The light leaked from the sides of the monitor is really bright still. Red plexiglass fixes this. (The monitor in question is a pretty old lcd panel, which is why it sits out of doors in my observatory...)

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You're right, they do charge more - compare a mac with a similarly specced PC and they're actually pretty cheap really, but most PCs aren't so well specced so they look expensive

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Since a lot of games have a gamma setting, I'm sure there must be a control for this in windows somewhere. It's called the display transfer table on OSX, or sometimes the gamma settings.. if these controls exist in windows it should be pretty easy to write the same software for windows. If it doesn't exist already..?

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I tried it on my Dell 3007 WFP monitor with an app I found that directly writes directly to the monitor via DDC. It could only dim the monitor by about 50%. I don't think the monitor will permit you to go lower than this. (And DDC is writing directly to the monitor - telling it to dim. If the monitor won't do it, then it just won't.) To what extent this is possible and allowed by the panel is going to vary from panel to panel.

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Yeah, I get about the same 50% on my imac. I don't think that's suitable for dark site use.. even with everything cranked up, the whole screen is a glowing grey. I don't get any leakage from the edges though, only from the screen itself - I guess it depends on how well the screen bezel fits, I've seen lots of screens with a big glowing gap around the edges.

The laptops though go MUCH darker than this screen. Both my powerbook and the macbook pro I've tried will actually turn the backlight off completely on the lowest setting, and with the light on minimum it's probably at 10% brightness or something. Maybe somebody at apple writes screen firmware in the day, and does astronomy at night?

It's really laptops that are going to get used out in the field, so if the mac laptops have sufficient range, I'm happy. For PC, it could be a real nightmare.. you'll get the full range. Everything from super-dark screens to netbooks that leak more light than they shine through the screen and have a brightness range that goes from "too bright" to "record breaking" It's going to be down to people on site to manage it still, no matter how good the software is.

DCC: Is that used in laptops too, or only for external displays? Some of the controls I've played around with have been through the PMU rather than the display stuff, I'm setting backlight brightness through a core graphics API, but I suspect the same controls are available more directly somewhere. Then it depends on where and how the permitted range is set I guess..

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I'll see if I can look up the APIs for this. I am sure this is possible in windows.

One advantage to your solution is that it will be very nice for devices with touch screens. Red plexiglass is no solution for such devices!

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Good luck with it! Do check if there's already software doing the job though. There's very similar software on the mac like dark adapted and nocturne. Neither are exactly perfect (they both fail with the screensaver for example), but to be honest I'd have just used nocturne if I didn't want these features built into my imaging application

Speaking of which, there's an important thing to note about this technique: you lose all green + blue colours. If you're imaging, and trying to capture a faint blue object, you're not going to see it on the screen because there's no red. Ideally you convert to greyscale, then apply the gamma trick, but that's both tricky and expensive to do for the whole screen.

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