11 Replies Latest reply on Mar 7, 2008 7:51 AM by Tim Lookingbill

    Calibration help reduce banding?

    Vernal Bogneris Level 1
      I'm using a 20" Apple Cinema Display on a G5 and am seeing some pretty horrific banding at times. I will be lobbying for some hardware calibration gear soon here at the office (regardless of banding issue) but does anyone know whether calibration can reduce banding at all?
        • 1. Re: Calibration help reduce banding?
          Level 1
          Depending on how it's calibrated, it can actually introduce more banding - if the correction is done in the lookup tables in the video card, and on 8 bit data, which, I think is the case with your display. Remember that an 8 bit per channel monitor starts out with a theoretical maximum of 255 levels per channel, and the correction that the calibration applies reduces that substantially. If you have a big enough difference between the natiive uncalibrated state of your monitor and your actual calibration, you can run into on screen banding that is not part of your image. That's why the higher end monitors apply the calibration correction to 10 or 12 bit data internally before passing it on to the video cards.
          • 2. Re: Calibration help reduce banding?
            Vernal Bogneris Level 1
            I see. Thanks for the informative post.
            • 3. Re: Calibration help reduce banding?
              Tim Lookingbill Level 1
              If you take your time with Apple's eyeball calibration utility you can get rid of all banding but at a slight loss destinguishing between spectral highlite regions like 250 and 255 RGB gray.

              I use the eyeball calibrator on my 2004 iMac and there's no banding at all but I do get it using i1 Display hardware calibrator. The Apple calibration utility is the best eyeball calibrator for LCD's I've ever come across.
              • 4. Re: Calibration help reduce banding?
                (Marco_Ugolini) Level 1
                I don't mean to sound overly critical, but no banding at the expense of color accuracy doesn't sound like a good tradeoff to me. No matter how hard you try, eyeballing will *not* give you accurate results. Fixating on an absolute absence of banding is the wrong thing to focus on.

                If banding occurs with your monitor when calibrating and profiling at a chosen correlated color temperature using a colorimeter and a monitor profiling application, try selecting the Native White Point option instead. That alone will reduce banding by a good deal.
                • 5. Re: Calibration help reduce banding?
                  Tim Lookingbill Level 1
                  Marco,

                  I get color accuracy as well using Apple's eyeball calibrator. Like I said there's no difference in CM images using either the i1 or the eyeball profiles on my 2004 iMac except as indicated.

                  I did have to spend quite a bit of time making sure each raster target was equally adjusted between the 5 steps. It took about three tries and a very warmed up iMac.
                  • 6. Re: Calibration help reduce banding?
                    Level 1
                    Tim,

                    If you have something to compare to, then your eye is a very good tool, but on its own, it's not so good. The big advantage of the colorimeter is repeatability.
                    • 8. Re: Calibration help reduce banding?
                      Tim Lookingbill Level 1
                      Repeatability?...Makes a lot of sense but in practice I don't see it with any calibration device be it eyeball or with my i1 Display.

                      I can recalibrate with the i1 Display three times one after another and there is always some shift in density distribution and/or neutrality with varied areas of banding with each profile. One will be reddish neutral the next will be greenish. It's subtle and can only be seen selecting each one in the Display Utility one after another.

                      The same goes with the eyeball calibrator only I don't get banding if I work at it.

                      What I wish these hardware calibrators would include is the ability to manually tweak the TRC curves at any given point much like curves in Photoshop. This is what Apple's eyeball calibrator enables you to do but in a much cruder way.
                      • 9. Re: Calibration help reduce banding?
                        (Marco_Ugolini) Level 1
                        >I can recalibrate with the i1 Display three times one after another and there is always some shift in density distribution and/or neutrality with varied areas of banding with each profile.

                        If you change the parameters, sure. Or if your colorimeter is faulty and unreliable, sure.
                        >The same goes with the eyeball calibrator only I don't get banding if I work at it.

                        "The same"? The *exact* same? I have difficulty accepting that, based on my experience. Your eyes (anyone's eyes) are good at perceiving *relative* values, not *absolute* ones. I still have to meet a person with "colorimeter eyes". :-)
                        • 10. Re: Calibration help reduce banding?
                          Ramón G Castañeda Level 4
                          It's rare for a human being even to have the same color response in both eyes. You can easily test that by covering one of your eyes at a time.
                          • 11. Re: Calibration help reduce banding?
                            Tim Lookingbill Level 1
                            Marco,

                            There was no changing of parameters-native color temp, 95cd/m2 and 2.2 gamma with each profile. And my i1 puck is kept wrapped in plastic away from dust and light which is recommended by Xrite/Gretag FAQ. Also I run the diagnostic utility and it passes.