Adobe Photoshop CS5 for Photographers - Martin Evening [49]
Luminance
You need to make sure that the brightness of the LCD display is within an acceptable luminance range. The target luminance will vary according to which type of display you are using and a typical modern LCD display will have a luminance of 250 candelas m 2 or more at its maximum luminance setting, which is way too bright for image editing work in subdued office lighting conditions. A target of around 120–140 candelas m 2 is ideal for a desktop LCD display and for laptops the ideal luminance to aim for is around 100–110 CD m 2.
Display gamma and brightness
Note that the gamma you choose when creating a display profile does not affect how light or dark an image will be displayed in Photoshop. This is because the display profile gamma only affects how the midtone levels are distributed. Whether you use a Mac or PC computer, you should ideally choose the Native Gamma or a gamma of 2.2.
It is important to note that as displays get older they do tend to lose brightness, which is one of the reasons why you will need to use a calibration device like the X-Rite i1 Photo shown in Figure 2.4, to recalibrate from time to time. There may also come a point where the display becomes so dim that it can no longer be successfully calibrated or considered reliable enough for Photoshop image editing.
The Macintosh 1.8 gamma option
The link between 1.8 gamma and the Macintosh system dates back to the early days of Macintosh computing when the only printer you could use with the Mac was an Apple black and white laser printer. At the time, it was suggested that the best way to match the screen appearance to the printer was to set the monitor gamma to 1.8. I once asked an engineer who designs display calibration software why they still included 1.8 gamma as an option and he replied that it's only there to comfort Mac users who have traditionally been taught to use 1.8. So now you know.
Device calibration and measurement
With the i1Match software you will be asked to calibrate the device (Figure 2.6) before proceeding to measure the brightness of the display (Figure 2.7). It is at this stage that the Luminance indicator appears and you can tweak the display brightness until the target luminance is reached.
Figure 2.6 Here, i1Match asks you to calibrate the device, by placing it on the base unit to measure the white tile, before hanging the device over the screen.
Figure 2.7 In this step you are asked to set the contrast to maximum (skip this step if calibrating an LCD) and then adjust the brightness. i1Match measures the current display brightness and shows you the measured value in a separate window. You can then adjust the display hardware brightness controls until you get a good match.
The profiling process
When you click on the forward arrow button in Figure 2.7, i1Match will start flashing a series of colors on the screen, while the calibration device measures them. Once it has completed doing this, it generates a display profile named with today's date. All you have to do then is click OK to establish this as the new display profile to use so that it replaces the previous display profile. You might also want to set a reminder for when the next monitor profile should be made. With LCD displays, regular calibration is not quite so critical and it will probably be enough for you to profile the display just once a month or so. Also, do you really need to hang on to old display profiles? I recommend that you purge the Colorsync Profiles folder on your system of older display profiles to avoid confusion. All you really need is one good up-to-date profile for each display.
Is the display too bright?