Professional Information Technology-Programming Book part 19 potx

Making Multiple Exposures in Camera Raw Now that you know how to use and make adjustments in Camera Raw, we've come to one of the more creative benefits of using the programto use the R

4.8 Using Camera Raw for Creating Effects

Most of your adjustments in Camera Raw will be for changing brightness, contrast, and other overall characteristics (such as noise, sharpness, and vignetting) using a tool that is completely nondestructive Most "effects" processing is terribly

destructive, which is why it is placed toward the end of the book and workflow (Chapter 11, to be specific) However, there are a few effects that you can at least begin in Camera Raw After all, the more nondestructive processing you can do for

an image, the better

4.8.1 Making Multiple Exposures in Camera Raw

Now that you know how to use and make adjustments in Camera Raw, we've come

to one of the more creative benefits of using the programto use the RAW files' larger range of brightness as multiple exposures There are basically two reasons you might want to do this: to create an especially interesting interpretation of the image by exporting the image as a particularly high-key or low-key interpretation (see Figure 4-34 and the next two sections of this chapter, "Increasing Dynamic Range by Making Multiple RAW Renditions" and "Increasing Dynamic Range Using the HDR Command") or to create exposures that can be combined to show detail in both the extreme highlights and shadows (see the two sections on HDR techniques later in this chapter)

Figure 4-34 Three different "exposures" of the same image, all made

approximately two f-stops apart in Camera Raw and opened in Photoshop Of course, as long as you haven't obviously under- or overexposed the image recorded

by the camera, the difference in exposure can be varied by as much as five f-stops

in Camera Raw

4.8.2 Increasing Dynamic Range by Making Multiple RAW Renditions

One of the great limitations of digital images is that present day printing methods ultimately force us to reduce our image data to 8 bits because that's all the printer can handle So the ultimate dynamic range is somewhat less than that of film and

we often suffer clipped highlights and shadows Of course, there are various ways

to get around that limitation One of the best is to simply create different

interpretations of the RAW file and then use a simple process to merge them

together so that we get detail in all the shadows and all the highlights

NOTE

Most of the time, I actually prefer this method instead of Photoshop's HDR

command (discussed in the "Increasing Dynamic Range Using the HDR

Command" section next) With this method, you're not limited to static subjects because you're making a pair of interpretations of the exact same moment that, when combined, show pretty much all the brightness and tone that you could

possibly see Also, it is easier to previsualize and produce the end result

In Figure 4-35, I use a photo of a forest just because there's so much brightness detail in that type of subject, but the nature of the actual subject matter matters little One thing you should be extra careful of is to watch your camera's Histogram

to make sure that all the tones are inside it The process is as follows:

Figure 4-35 The low-key and high-key "exposures" of the same RAW file

1 Go to Bridge and open your image in Camera Raw When you see the image

in the Camera Raw workspace, press Cmd/Ctrl-U until all the Auto

checkboxes are turned off Then create a low-key exposure, but don't worry too much about keeping detail in the shadows The overall image should look as though it's about two stops underexposed The most important thing

is to be sure that you see plenty of detail in the Highlights When you like what you see in the Preview window, click Open Your low-key image will open in Photoshop Be sure to leave it open

2 Reopen Bridge and reopen the same file in Camera Raw This time, make the adjustments so that you see plenty of detail in the darker midtones and the shadows These shadows are going to replace the shadows in the

previous (low-key) interpretation you just made, so make sure they contain plenty of detail At the same time, make sure that anything that needs to be black is black The best way to do this is to turn on the Shadows preview box You can see the results of both exposures in Figure 4-35

3 Click inside the overexposed or high-key image so that it's active and then choose Select Color Range The Color Range dialog appears (see Figure 4-36)

Figure 4-36 The Color Range dialog

4 Choose Highlights from the Select menu When the selection marquee

appears, click OK

5 Choose Select Feather Enter a feather radius large enough to give you plenty of blending I find that something around 150 pixels generally works

best for merging markedly different dynamic ranges, such as we have here, but you will have to experiment on individual images to get the best result If you select a feather radius that is too large, you'll lose a lot of detail in the midtones If the feather radius is too small, you'll get very unrealistic halos around darker-toned objects

6 Press Cmd/Ctrl-I to invert the selection and then Cmd/Ctrl-C to copy the contents of the selection to the clipboard

7 Make the low-key image active by clicking inside it Press Cmd/Ctrl-V to paste the contents of your selection layer into the low-key image You can see the final result in Figure 4-37

Figure 4-37 The Camera Raw Auto adjustment of the file (left) and the

"fake" HDR result after the merge of both Camera Raw exposures (right)

4.8.3 Increasing Dynamic Range Using the HDR Command

Although you can create HDR files from other formats, they work best when

created from RAW files, thanks to the extended range of data already in those files

The exercise described here works best when you use a series of three to five RAW files taken two full f-stops apart The camera should be on a tripod, you should use

a remote shutter trigger (or cable release), and your subject must be still as a stone You must not change the aperture or focus, so it's best to shoot in Manual mode for both exposure and focus and to shoot in RAW mode

Once you've done all that, upload the pix to your computer Although it's possible

to process HDRs directly from the Bridge Tools menu, don't You'll get much better results from the following sequence of steps:

NOTE

If your camera can shoot a sequence two full f-stops apart in a bracketed sequence, you may be able to shoot an HDR sequence without a tripod (but you still need to

be very steady when shooting) Be sure to put the camera in Aperture Priority mode to force the bracketing by shutter speed, rather than by changing aperture or ISO It will help a lot if you can at least brace the camera against a lamppost, tree,

or railing At the very least, don't breathe or wiggle in the slightest If you do risk handheld sequences, be sure to check the Auto-overlap box in the Merge to HDR dialog that opens when you choose File Automate Merge to HDR

1 In Bridge, select the images you want to merge, then press Enter/Return to open them in Camera Raw

2 Click the Select All button to select the entire sequence If you think there are too many in the set or that some exposures are too close together, press Cmd/Ctrl and deselect those you don't want to include

3 Press Cmd/Ctrl-U once or twice until all the Auto boxes are turned off You should now see a distinct one or (better) two-stop difference between the brightness of each of the thumbnails

4 Leaving the chosen thumbs selected, click the Open button Each image will open in a separate window in Photoshop

5 In Photoshop, choose File Automate Merge to HDR A Merge to HDR dialog that looks similar to the Camera Raw multiple exposure dialog will open Be sure to click the Attempt to Automate box at the bottom if you attempted to shoot a handheld sequence From the Use menu, choose Open Files Click OK Wait and watch

6 After a few frames have popped up, they'll give way to a full screen dialog called Merge to HDR (See Figure 4-38.) You'll see the images you picked fill the screen On the left are the thumbs of the RAW images you picked just as the camera recorded them, with no adjustment In the center, you'll see the results of the merge On the right, you see a bit depth menu, a

Histogram, and a slider Move the slider until the overall brightnessand the white pointare exactly where you want them to be Never mind if this image itself looks weak in the shadow tones Leave the Bit Depth menu choice at

32 bits

Figure 4-38 The Merge to HDR dialog

NOTE

You can click the Browse button and browse for files to include in the

merge, but there's no way to visually identify RAW files because there are

no thumbnails

7 A new file opens that is titled Untitled HDR If you want to save up your image for the day when you can actually make use of all that brightness information in some future version of Photoshop, save the file as a Portable Bit Map file

8 You now have two choices for finally adjusting the file If you want to adjust

it in 32 bits, your only choice is Image Adjust Exposure You can see

the Exposure dialog in Figure 4-39 The Exposure dialog pops up Drag the sliders until you like what you see and click OK

Figure 4-39 The Exposure dialog

If you want to use the usual adjustment commands, you'll have to convert the file to 16 bits You can convert to 8 bits, but why throw out that much data when you've gone through the trouble to collect it? At least keep it to 16 bits until you've finished doing all your work on the file Then you can make

a copy, flatten the layers, and reduce the bit depth for publication without destroying all the work you did on the original, which you may want to change someday without having to do it all over again Choose Image

Mode 16 bits An HDR Conversion dialog appears, as shown in Figure

4-40

Figure 4-40 The HDR Conversion dialog

9 You now have several methods you can choose from to interpret the final version of the image You'll probably find Exposure and Gamma the most useful The sliders are extremely sensitive, so start by getting the Exposure adjusted to something close to what you want as an end result Now adjust the overall contrast with the Gamma slider These are subjective

adjustments, so just experiment until you like the results You can see my results from the original images I shot in Figure 4-41

Figure 4-41 The final result from the Exposure and Gamma dialog Of

course, you'd crop out the railing, but not until further along the workflow

Since you now have a standard 16-bit Photoshop file to work with, you can use any

of the Photoshop commands to further enhance this image Of course, some

Photoshop commands and adjustments work only in 8-bit mode, so you should wait until you're further along in the workflow before applying those commands or you'll lose a large percentage of your brightness information

4.8.4 Create a High-Key Version of the Image

High-key images are those that are very bright in tone and have few (if any) deep