History and Virtual Layers

Layer-based edits offer great freedom and flexibility, but they have one major disadvantagethey make large files that can also be dauntingly complex. It's often a sobering exercise to return to a layered file you created months or years ago and try to figure out what each layer was supposed to do. Layer naming helps, but only up to a point.

We confess that when the History feature first appeared in Photoshop, we saw it as little more than a massively overengineered multiple undo. But our friend and colleague Jeff Schewe, who has probably had more influence on the History feature's development than anyone outside of Adobe, dropped some hints that made us realize the error of our ways.

History certainly gives you many levels of Undoup to 1,000but it does much more besides. When you use History in conjunction with blending modes and the History Brush, you have something that lets you apply very similar effects to those you can achieve with layers and masks.

Virtual Layers

We like to think of History as providing "virtual layers" because it lets us do many of the things we can also do with layers. But let's look at the important ways in which History's virtual layers differ from real ones.

  • History is ephemeral. It's only around as long as your file is open. Once you close the file, its history is gone forever, giving a whole new twist to the old adage that those who can't remember history are doomed to repeat it. You can't save History with the file, so you have to get your edits right before you close. (You can save a history log, either in the file's metadata or in a text file, but the log doesn't let you re-create previous states of the image.)

  • History is easier than layers when you know exactly what you're doing and can get things right on the first (or possibly second) try, but if you're less decisive than that, it quickly becomes more work than using layers to achieve the same effects.

  • History can be even more demanding on your hardware than adjustment layers. It requires plenty of scratch space, and the faster the disk, the better.

Nevertheless, History is a powerful feature for making quick, effective, dare we say gonzo, edits.

History Tools

History works using just a handful of tools. The History palette lets you set the source for your History-based editsthe pixels that you'll apply to the image (see Figure 7-52).

Figure 7-52. The History palette

The History palette

The History palette lets you click in the left column to set the History source to a History state or snapshot (the paintbrush icon indicates the current History source), or click on a snapshot or History state's tile to set the current state of the image.

The three icons at the bottom of the palette let you create a new document from the current History state, create a new snapshot, and delete the current History state, respectively. Snapshots are a convenience featurethey're usually easier to track than History states, and unlike History states, you can name them.

Applying History

You can apply History using either the History brush tool or the Fill command from the Edit menu. Fill is easier when you have a selection or you want to affect the entire image. The History brush is useful for actually brushing in edits. When you use either one, you can immediately use the Fade command (on the Edit menu) to adjust the edit's opacity (and hence its strength).

Figure 7-53 revisits the image from Figure 7-18, but this time we'll make the edits using History instead of layers. No masking is involved, so we simply use Fill from History to make all the edits.

Figure 7-53. Simple History edits

The process is very simple. Our first edit was a layer set to Multiply with an opacity of 83 percent, so we set the History source to the current image state (actually, since the image is newly opened, it's already set that way), and choose Fill from the Edit menu. In the Fill dialog box, we choose History from the Use menu, Multiply from the Mode menu, and 83 percent for the opacity.

Our second edit was an Overlay layer set to 100 percent. Again, we set the History source to the current image stateotherwise the Overlay blend would use the original image rather than the image after Multiply, and hence wouldn't match the layered version. Then we choose Fill, and the dialog box choose History, Overlay, and 100 percent.

Our final edit was a solid color layer set to Color blend mode with an opacity of 20 percent. For this, we don't need to use a History state. We simply set the background color (or foreground color, if you prefer) to our desired color (in ProPhoto RGB it was R 156, G 107, B 123), then we choose Fill, and in the dialog box, we choose Background color from the Use menu, Color from the mode menu, and 20-percent opacity.

The result is pixel-for-pixel identical to the layered version we produced earlier in the chapter. We don't have any layers to tweak, but we could, if we wished, fine-tune by continuing to blend the different History states.

Combining Blend Modes with History

History also lets you do things that you can't do as easily with layers. One trick we often use is to make a basic setup of three snapshots, one for the original image, a second darkened with Multiply, and a third lightened with Screen. Then we apply the darkened and lightened versions using Soft Light or Hard Light/Overlay to darken or lighten while adding contrast.

Figures 7-54 and 7-55 show a quick set of edits performed entirely with History. We don't necessarily advocate using this approach for all, or even most, edits, but it's one more useful set of techniques to get under your beltthe more techniques you master, the easier it is to pick the one that will get you the results you want with the minimum of effort in any given situation.

Figure 7-54. Setting up Snapshots

Figure 7-55. Applying the edits

In this case, the unedited image is flat, so we want to pump up the contrast. Specifically, we want to darken the sky, then add contrast to the sagebrush while brightening the highlights. To do so, we first set up a series of snapshots that lighten and darken the image using Screen and Multiply, as shown in Figure 7-54.

Next, we apply the edits. We make a selection of the sky and fill it from the Multiply snapshot. Then we invert the selection, and use the History brush to paint the Screen snapshot into the sagebrush, using Overlay blending to increase contrast, as shown in Figure 7-55.

The trick here, of course, is that you can create a snapshot using one blend mode, then apply it using a different mode either by choosing it in the Fill dialog box, or by setting the blend mode for the History Brush.

Print Optimization

As with the wet darkroom, the goal when working in the digital darkroom is often to make printsotherwise the digital darkroom wouldn't be worthy of the name. But the digital darkroom offers a key advantage over its analog counterpart: Thanks to the wonders of color management, it lets you see what will happen in the print before you make it.

The naïve view of color management is that it makes your prints match your monitor. If you've read this far, you've probably realized that this is an impossible goalprinters simply cannot print the range of color a good display can display. Instead, color management tries to reproduce the image as faithfully as the limitations of the output process will allow.

But color management knows nothing about images; it only knows about the color spaces in which images reside. So no output profile, however good it is, does equal justice to all images. When you convert an image from a working space to the gamut and dynamic range of a composite printer, the profile treats all images identically, using the same gamut and dynamic range compression for all.

But thanks to Photoshop's soft-proofing features, you can see ahead of time exactly how the profile will render your images, allowing you to take the necessary corrective action. If you want great rather than good, you need to optimize images for different output processes, because something always has to give, and each image demands its own compromises.

Adjustment layers provide a very convenient method for targeting images for a specific output process. You can use adjustment layers grouped in layer sets to optimize the same master image for printing to different printers, or to the same printer on different paper stocks. The following technique uses three basic elements.

  • A reference image. Create a duplicate of the image, with Proof Colors turned off, to serve as a reference for the image appearance you're trying to achieve.

  • A soft proof. Use the Proof Setup command to provide a soft proof that shows how the output profile will render the image.

  • A layer set containing adjustment layers. Group each set of optimizations for a specific output condition (printer, paper, ink) into a layer set, so that you can turn them on and off conveniently when you print to one or another device.

Making the reference image

Choose Duplicate from the Image menu to make a duplicate of the image. The duplicate will serve as a reference for the appearance you're trying to achieve on the print.

You need to make a duplicate rather than simply open a new view because you'll be editing the master image to optimize it for the print, and the edits would show up in a new view. The duplicate isn't affected by the edits you make to the master file, so it can serve as a referencea reminder of what you want to achieve in the print.

Setting the soft proof

Choose Custom from the Proof Setup submenu on the View menu to open the Proof Setup dialog box. Load the profile for your printer, and check Paper Color to make Photoshop use absolute colorimetric rendering to the monitor (see Figure 7-56). We find that all the soft-proof views (using the different combinations of Paper Color and Black Ink) tell us something useful, but the absolute colorimetric rendering produced by checking Paper Color is, in theory at least, the most accurate.

Figure 7-56. Setting the soft proof

However, the first thing you'll notice is that checking Paper Color makes the image look much worse. Sometimes it seems to die before your eyes. At this point, a good many people think Photoshop's soft proof must be inherently unreliable and give up on the whole enterprise. What's really going on is that Photoshop is trying to show you the dynamic range compression and gamut compression that will take place on printing.

The reason the soft proof looks bad at first glance is that Photoshop can only show you the gamut and dynamic range compression within the confines of your monitor space, and it can only do so by turning things down, so white in the image is always dimmer than your monitor white.

A second problem is that the vast majority of monitor profiles have a "black hole" black point (a black with a Lightness of zero in Lab). Real monitor black typically has a Lightness of 3 or higher, so the soft proof typically shows black as slightly lighter than it will actually appear on the print.

Typically, in the soft proof you'll see washed-out shadows, compressed highlights, and an overall color shift caused by the difference between the white of your working space and the white of your paper. Some images are only slightly affected by the conversion to print space, while with others the change can be dramatic. As with just about any proofing method we've encountered, you need to learn to interpret Photoshop's soft proofs. You may find the following tips helpful in doing so.

Tip: Look Away When You Turn On Paper White

Much of the shock you feel when you see Photoshop's absolute colorimetric rendering to the monitor stems from seeing the image change. If you look away from the monitor when you turn on Paper White, your eyes will be able to adapt to the new white point more easily.

Tip: Use Full-Screen View to Evaluate Soft Proofs

Your eyes can't adapt to the soft-proof white point unless you hide Photoshop's user interface elements, a good few of which are still pure white. Press F to switch to full-screen view with a neutral gray background, then press Shift-F to hide the menu bar. Press Tab to hide all the palettes. Now you can see the soft-proofed image on a neutral background with no distracting elements to bias your vision.

A further problem, particularly with vendor-supplied profiles for older printers, is that they weren't built with soft-proofing in mind. They do a good job of converting the source to the output, but they don't do nearly as good a job of "round-tripping"converting the output back to a viewing profile. That said, all the profiles we've built with current third-party profiling tools make the round-trip very well.

If all this seems discouraging, take heart. Soft-proofing for RGB output may have passed its infancy, but it hasn't yet reached adolescence. And problems with profiles aside, the soft proofs offered by Photoshop are not, in our experience, any less accurate than those offered by traditional proofing systems. You simply need to learn to "read" them. Figure 7-57 shows some examples.

Figure 7-57. The soft proof and the reference image

Make your edits

We suggest starting out viewing the soft proof and the reference image side-by-side. Once you've edited the soft-proofed image to get it back to where you want it to be, fine-tune your edits looking at the soft-proofed image in full-screen view.

Some images need minimal editing; others may require significant reworking. We start by applying adjustment layers to get the soft-proofed image to match the reference (the duplicate) as closely as possible. Then we group these adjustment layers in a layer group named for the print process it addresses. That way, we can easily optimize the master image for different print processes by turning the layer sets on and off, without having to create a new file for each print condition. Figure 7-58 shows the edited and reference images with the individual edits and their accompanying layer sets.

Figure 7-58. The edited image and the reference image (part 1)

Figure 7-58. The edited image and the reference image (part 2)

This technique is particularly useful when printing to inkjet printers directly from Photoshopwe can keep a single RGB master file, with built-in optimizations for each print condition, and let Photoshop do the conversion from RGB working space to printer space at print time. But it's also valuable when preparing images for CMYK output, which often involves, if anything, greater compromises. We may do final fine-tuning on the converted CMYK image, but we make heavy use of soft-proofing to get the RGB image into the best possible state to withstand the conversion before we actually make it.

Once we've edited the soft-proofed image to match the reference image, we use full-screen view to take a final look at the soft-proofed image prior to printing. (We prefer the gray background, with the menu bar hiddenthe black background makes the shadows look too light.) In the majority of cases we find that no further editing is necessary, but occasionally we'll fine-tune highlight and shadow detail.

The final step is, of course, to print the image. See "Imaging from Photoshop" in Chapter 13, Image Storage and Output.

Real World Adobe Photoshop CS2(c) Industrial-Strength Production Techniques
Real World Adobe Photoshop CS2: Industrial-strength Production Techniques
ISBN: B000N7B9T6
Year: 2006
Pages: 220
Authors: Bruce Fraser

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