X-Rite i1Display Pro Advanced Features | Contrast Ratio with Coloratti Andrew Rodney
by Brenda K. Hipsher – July 26th, 2011
In the coming few days we’re going to look at some of the advanced features of the NEW i1Display Pro monitor and projector profiling solution from X-Rite. The first new feature is called “Contrast Ratio” and is found in the advanced mode of of disiplay profiling in i1Profiler software from X-Rite. This is a feature that we have not seen in software packages often and I’ll admit it was new to me! So I asked for some help with understanding this feature and Coloratti Andrew Rodney. Andrew was kind enough to write a guest blog on this feature for us. Special thanks to Andrew for taking the time to help us understand Contrast Ratio. Here we go!
Contrast Ratio Feature in X-Rite i1Profiler
When we calibrate a display, we specify what are called target calibration aim points. We inform the software that we want a certain White Point or Luminance (specified in cd/m2) of backlight intensity. These aim points are selected to produce a visual match between the display and the print viewed next to it. Therefore, the correct values are those that produce a visual match between these two items.
The new i1Profiler software provides another useful and important target calibration aimpoint: Contrast Ratio.
To understand what this aim point does, and why its so useful, consider what contrast ratio describes. Its the range between the brightest white and darkest black. Contrast ratio is described using a scale such as 300:1. In this example, the brightest white is 300 times brighter than the darkest black. The higher the value, the greater the range between black and white. Here’s the math for figuring out the contrast ratio of a display: Divide the white luminance by the black point. If you calibrated the luminance to 150cd/m2 luminance and a black point of .25, that would result in a 600:1 contrast ratio between the brightest white and darkest black of this display.
Modern LCD displays are capable of producing very high contrast ratios. Manufacturers of such displays like to provide these high values as they are attractive for those playing video games or viewing video content. Yet these high values are not useful for those processing images and desiring a good soft proof between a display and a print.
On a very glossy paper stock, using a very black ‘photo ink‘, this print may provide a 300:1 contrast ratio. Yet your display may have a contrast ratio of 800:1, 1000:1 or higher. If you soft proof in Photoshop and use the Simulate Paper Color and Ink Black check boxes found in the Customize Proof Setup (Fig 1), Photoshop uses the ICC printer profile to adjust the print contrast ratio onto the display. The results are often disappointing because you see this very high contrast ratio display become dim as the proper contrast ratio for print viewing is simulated. It is far better to calibrate the displays contrast ratio rather than adjusting the ratio solely by using the paper and ink simulations in Photoshop. When using just Photoshop to do this simulation, only the image, not the rest of the user interface is adjusted which is far from ideal.
This is where i1profiler’s new contrast ratio target calibration aim point comes into play. If you know you will be viewing a glossy print and you wish to have a better match of the screen to the print, start with a target calibration of around 300:1 and compare the image being soft proofed on the calibrated display with the print properly illuminated next to that display. You may need to raise or lower that setting until you get a better match. The same is true for adjusting the white point and luminance! For matching to matte papers, a 200:1 contrast ratio may be a good starting point.
Its not possible to provide an exact value! It takes trial and error to produce the best settings because everyone’s print viewing conditions, inks, papers and display are different. The idea is to control not only the target calibration aim points for white point and luminance for a print match but contrast ratio too. When soft proofing in Photoshop, with the paper profile loaded and the two simulate check boxes on, you should see a very good screen to print match. The key is the appropriate calibration target values, and setting the contrast ratio has a profound effect.
Seems like this is a case of “less is more” and now you can control the contrast ratio of your monitor profile with i1Profiler software. This software is packaged with i1Display Pro, i1Photo Pro, i1Publish Pro, and i1Publish software. If you already own and i1Pro spectrophotometer you can get this and other great features of i1Profiler software by upgrading your device.