Adobe Photoshop CS5 for Photographers - Martin Evening [91]
How to clip the shadows
Setting the black clipping point is, by comparison, much easier to decide. Put aside for now any concerns you might have about matching the black clipping point to the printing device, I'll explain how that works over the next two pages. Blacks slider adjustments are simply about deciding where you want the shadows to clip. The default setting is 5 and this will usually be about right for most images. You may want to ease the clipping off to around 2 or 3 on some images, but it is inadvisable to take the setting all the way down to zero. Some photos such as the one shown below in Figure 3.33 can actually benefit from a heavy black clipping so that the dark areas print to a solid black.
Figure 3.33 In this picture of my daughter, Angelica, you can see that the blacks in this photo are well and truly clipped. This is because I deliberately wanted to force any shadow detail in the backdrop to a solid black. As you can see, the color sampler over the backdrop in this picture (circled) showed an RGB reading of 0,0,0.
Hiding shadow noise
Raising the threshold point for where the shadows start to clip is one way to add depth and contrast to your photos. It can also help improve the appearance of an image that has very noisy shadows.
Shadow levels after a conversion
You will sometimes come across advice saying that the output levels for the black point in an RGB image should be set to something like 20,20,20 (for the Red, Green, Blue RGB values). The usual reason given for this is because anything darker than, say, a 20,20,20 shadow value will reproduce in print as a solid black. Just to add to the confusion, different numbers are suggested for the output levels: one person suggests using 10,10,10, while another advises you use 25,25,25. In all this you are probably left wondering how to set the Blacks slider in Camera Raw, since you can only use it to clip the black input levels and there is no control for setting the black output levels so that they match these suggested output settings.
Is it wrong to set levels manually?
All I am suggesting here is that it is an unnecessary extra step to use Photoshop to set the black output levels to anything higher than the zero black after you have already set the black clipping at the Camera Raw editing stage (or done so in Photoshop). If you do set the black output levels manually to a setting that is higher than zero you won't necessarily get inferior print outputs, providing that is, you set the black levels accurately and don't set them any higher than is needed. And there's the rub: how do you know how much to set the output levels, and what if you want to output a photo to more than one type of print paper? You see, it's easier to let Photoshop work this out for you automatically. Some picture libraries are quite specific about how you set the output levels, but their suggested settings are usually very conservative and unlikely to result in weak shadows when printed to most devices. It is therefore probably better to oblige the libraries and just give them what they ask for, rather than fight them over the logic of their arguments. The only time when you may need to give special consideration to setting the shadows to anything other than zero is when you are required to edit an already converted CMYK or grayscale file that is destined to go to a printing press, where the black output levels have been set incorrectly. However, if you use Photoshop color management properly you are unlikely to encounter such problems.
This is one of those areas where the advice given is more complex than it needs to be. It is well known that because of factors such as dot gain, it has always been necessary to make the blacks in a digital image slightly lighter than the blackest black (0,0,0,) before outputting it to