Color temperature conversion

My new laptop’s screen seems to use 9300K for its white point. I would prefer it use 6500K, like my old monitor does. While there’s no direct color temperature control, I can do color correction, with options for brightness and contrast of each color in RGB.

So, my question is: does anyone know of a chart or formula that would allow me to make the modification using those controls? I would really like to be working at 6500K, which also happens to be the industry standard for photo manipulation.

You would need to know what that particular laptops’s contrast and brightness controls actually meant at each setting. There is no standard, or even much consistency about this, and so any conversion chart that said “set contrast to 8.2” would be pretty much useless. Even for brightness and contrast controlled entirely in software this remains so as there is no standard for the final conversion function from digital value to on-screen luminance. You don’t know the shape of the transfer curve, or even necessarilly your place upon it.

What you really need, is a proper calibration tool - which means a physical device that sits on the screen and talks to software to work out how to get the best possible colour profile. For critical work, professionals will recalibrate screens frequently, as there can be aging and temperature related shifts.

Yeah, I know there’s no way I can get it exact, but I was hoping that there would be a rough guide based on some common assumptions. It’s not like I actually do professional work with this netbook: I just noticed that my screen seems a bit too blue, and merely decreasing the brightness of the blue doesn’t seem to fix it, and I can’t increase red and green simultaneously, making it hard to go by sight alone.

I knew I wouldn’t get an exact number, but I was hoping to get a formula that I could use as a guideline, and then tweaking from there. I mean, assuming that the conversion curve was consistent between the two monitors.

Dunno if you would prefer the same picture as your tv but if you do and you have a dvd player, you can pop in any [THX Certified movie](THX Certified movie) and calibrate with their THX Optimizer in the movies menu. Windows 7 has a color calibration in the display setting, I wouldn’t be surprised if Vista and XP did too. They have freeware calibration apps online as well and online calibration pages. They even go as far as Professional and expensive software with special hardware to calibrate your monitor.

9500k has a blue tint, if you can’t get rid of that easily, maybe your screen is bad.

I’m not familiar with Windows, but inspired by this thread to have a further investigation on my Mac, I was surprised just how good the software calibration of the display can be for creating a visually acceptable profile. The Mac creates an appropriate colour profile for each display, and applies the correction in the display driver, not in the display itself. I would imagine Windows can do something similar. This is the right place to do it. Fiddling with the contrast and brightness on the display itself isn’t.

I have a very very old Mac laptop that was showing a clearly off colour. I had put it down to age, and really didn’t think much of it. It provides a backup capability for me for trivial stuff, and I really don’t otherwise care. But just using the visual calibration tool made a huge difference. I am rather amazed.

Well, my new PC is a netbook, and has a crappy graphics card. The settings I was changing are in the driver, but it didn’t even come with a built in calibration image, let alone the software calibration wizards I’m used to from other computers, so I was flying blind.

Thank you very much for the information. I knew about calibration images online, but, for some reason, the idea of using one didn’t occur to me. Since the standard white point is 6500k, just using one of those images helped me get rid of the blue tint.

Unfortunately, actual calibration is impossible, as even a slight change in the vertical viewing angle changes the gamma. But at least the annoying blue tint is gone.

It’s may be a cheap screen, but at least that much is fixable. I can’t complain too much, as I got a $400 netbook for $100.