5 Replies Latest reply on Jan 11, 2008 9:29 AM by Lou Dina

    Difficulty getting correct moniter luminance when calibrating

    Matthew A Kraus Level 1
      I am calibrating my LCD moniter with a Colorvision Spyder. I am having a little trouble getting my moniter brightness right.

      Im really getting confused between Contrast, Brightness and White Luminance!

      1. What is White Luminance and how do I adjust it?
      2. What is the relationship between contrast and brightness in an LCD?
      3. Should I use the front Brightness and Contrast controls on my moniter during the calibration process?
      4. If so, what order and specifically how do I use them.

      Thanks,
      Matthew Kraus
        • 1. Re: Difficulty getting correct moniter luminance when calibrating
          Lou Dina Level 3
          Matthew:

          1. What is White Luminance and how do I adjust it?

          White luminance is "brightness level" your colorimeter or spectrophotometer sees when measureing a pure white patch (RGB=255,255,255) during monitor calibration. I typically set mine around 85-90 cd/m2 (candelas per square meter) in my software. I'd keep it under 100 if a good monitor to print match is important to you. If you do mainly web based work, feel free to set it higher, perhaps 120 or so.

          2. What is the relationship between contrast and brightness in an LCD?

          Hmmmm...not always an easy question to answer. Sometimes the controls are reversed. Ideally, brightness should adjust the intensity of your LCD backlight to make the overall appearance brighter or darker. And contrast should move the white and black endpoints closer or further apart from one another, changing the overall contrast level. It's not always clear.

          3. Should I use the front Brightness and Contrast controls on my moniter during the calibration process?

          I have a Samsung Synchmaster 213T LCD hooked up to a digital video card. When I go to calibrate, the software sees that I have a digital card, and it disables all controls on the monitor panel EXCEPT the brightness control (ie, the intensity of the backlight). So, I tell the software I want a white luminance of 90 cd/m2 and adjust the intensity of the backlight (brightness) until I get the right luminance reading (the software should tell you when this is achieved). Unless you have a high end LCD monitor, all the adjustments made from the monitor control panel are written to your video card anyway. My software "sees" this and knows that the only real analog control I have on my monitor is the backlight brightness. Your situation may be the same or different. At any rate, you do want to get the brightness set about right.

          4. If so, what order and specifically how do I use them.

          Again, I'm not sure of your setup. I'd set the white luminance in your software to about 90 for starters, then do what the software tells you. I'd also select a gamma of 2.2. The color temperature can be anywhere between 5000K and 6500K, but I find I get a better color match as I get closer to 5000K. Others find 6500K to be good. I have mine set to 5200K and get a very good match.

          Hope that helps.

          Lou
          • 2. Re: Difficulty getting correct moniter luminance when calibrating
            Matthew A Kraus Level 1
            Lou,
            Thanks for the thoughtful and detailed answer. I just can't seem to get this figured out. I have a Samsung 214T moniter which I suspect is very much like your 213T. After I play with this a little more, would you mind if perhaps I could contact you offline so you could help me get through this process since it seems we have similar setups. If that would be OK with you, please let me know at MKraus1044@aol.com.

            Tnaks again,
            Matthew Kraus
            • 3. Re: Difficulty getting correct moniter luminance when calibrating
              Ramón G Castañeda Level 4
              Matthew,

              Just in case you're looking for info on Google or other search engines, watch the correct spelling of monit or.
              • 4. Re: Difficulty getting correct moniter luminance when calibrating
                Lou,

                What "digital" video card do you use? Before I read you post, I assumed all video cards were digital. Can you elaborate at bit?

                I am ordering a new Mac Pro (finally switching from PC), and I don't want to order the "wrong" video card.

                Thanks so much your input.

                Randy

                see some of my work: www.randygay.com
                • 5. Re: Difficulty getting correct moniter luminance when calibrating
                  Lou Dina Level 3
                  Randy,

                  My video card is a Matrox Parhelia card with 256MB memory. It has three connections on the back, one digital and two analog. I have my main monitor hooked up to the digital connection (more accurate) and my 2nd monitor (for palettes, etc) is connected to the analog port.

                  I suspect most good video cards sold today have a digital interface, but they may also have analog connections. Another thing to be aware of at least on a PC) is that if you want to have two calibrated monitors on a single video card, the card must have two video lookup tables (VLUTs), otherwise it will only be able to retain and load data on a single monitor. My Matrox card has a single VLUT, so when I boot up, it loads my calibration to the card and applies it to both monitors. I have found I can use Gretag's DisplayProfile.exe program (free download from the Xrite site) to load a different calibration for each monitor individually, but I have to do this every time I reboot. A two VLUT card will always remember to load the correct calibration data for each monitor.

                  I don't think Macs have this issue, but check with somebody in Mac-Land to find out for sure. At one time, some video cards didn't even support loading any data, but my guess is that those are el-cheapos and perhaps don't even exist anymore.

                  Lou