Photoshop cs5 cho nhiếp ảnh gia part 51 pdf

313 ■ EXPANDING DYNAMIC RANGE Try It! Open the images called CanyonDark and CanyonLight from www.sybex.com/go /photoshopnature and try combining them using the “cookbook” approach. Expanding Latitude via Merge to HDR Pro Photoshop CS5 dramatically overhauled and improved the Merge to HDR feature. Merge to HDR Pro is a tool to combine multiple exposures (ideally three to seven exposures of the identical subject, although technically you can use it with two images) into one 32-bit image. Using 32-bit enables the image to have a greatly expanded dynamic range so that the final image can contain detail in shadow areas and in highlights that normally cannot be present in a single image. In fact, 32-bit offers more latitude than what you can even see on your monitor. However, the 32-bit image can be immediately converted to 16-bit or even 8-bit. Merge to HDR Pro creates an image containing the maximum amount of detail and color information possible, with very little work on your part. It ensures that the transitions among the exposures are gradual, with no harsh obvious edges. It sounds too good to be true, doesn’t it? In earlier versions, nature photographers were likely to experience several dif- ficulties using this tool. If anything changed between exposures—a tree branch blow- ing slightly in the wind, a leaf, anything moving—Merge to HDR often failed to give a good final image. Similarly, if there was any camera movement, it also didn’t work. In CS5 the Auto-Align algorithms have been tremendously improved. In addition, you can add a layer mask to an image to hide part of an image to help with objects that move. Although there is still no option in this version of the tool to allow you to manually align the images, it works far better than earlier versions. Situations with high contrast and static subjects are best for creating HDR composites. If a scene lends itself to using Merge to HDR Pro, follow the same steps we described earlier for taking shots to expand exposure latitude. After you have downloaded your images to your computer, access Merge to HDR Pro through Bridge directly or through Photoshop using these steps: 1. To select the files to use in Photoshop, choose File > Automate > Merge to HDR. The Merge to HDR dialog box (see Figure 8.10) appears. Click Browse to select the desired images, and then click Open, or if you have already opened the images, simply select Add Open Files. 2. Check the Attempt to Automatically Align Source Images box. 3. To select the images to use directly from Bridge, simply highlight the desired images, and choose Tools > Photoshop > Merge to HDR Pro. If you have opted to have Bridge auto-stack your HDR images, it will be even easier to choose the right files. Just be certain to select all images in the stack, not just the top image. 607343c08.indd 313 4/11/10 11:06:42 PM 314 c h a p t e r 8: COMPOSITES ■ Figure 8.10 Select your desired images in the Merge to HDR Pro dialog box. 4. Click OK. 5. This leads to a Merge to HDR Pro dialog box, shown in Figure 8.11. You can zoom in to see the results more closely, if desired, or uncheck one of the source images displayed on the bottom to exclude it from being part of the final image. The image preview automatically updates to reflect this change. Don’t worry if initially the image appears somewhat flat or too dark or too light. There are a lot of controls available so you can modify the results to suit your vision. Figure 8.11 The Merge to HDR Pro dialog box allows you to preview the results of the merge as well as to ne-tune the results. 607343c08.indd 314 4/11/10 11:06:43 PM 315 ■ E XPAN DIN G DY NAM IC R ANG E Note: In the fly-out menu at the top right of the interface, leave the “response curve” set to auto- matic unless you have created a custom curve for your camera. The camera-response curve reflects how the camera’s sensor reacts to light. The precise sensitivity of each camera’s sensor differs, so ideally you need a response curve for each of your cameras if you do a lot of HDR work. There are several tutorials available on the Web to help you do this; search for how to create a camera-response curve. 6. Choose a bit depth for the merged image from the Bit Depth pull-down. Most of the time you’ll want to leave this at the default value of 16-bit. Working in 32-Bit Mode Choose 32-bit mode if you want to apply adjustments that work in 32-bit space, such as Gamma and Exposure, as a layer. Note that if you choose 32-bit, all the other options in the Merge to HDR Pro dialog disappear and you must press OK to continue, or change the mode back to 16-bit. After applying adjustments as layers in 32-bit mode, you must flatten the image in order for the adjustments to have their intended effect. Then go to Image Mode 16-bit to convert the image back to 16-bit space and continue with your workflow. If you don’t flatten the image before changing the bit depth, the adjustments will yield very unintended results. When you switch to 32-bit mode, you’re creating a true HDR image with more data than can be displayed on the screen at once. When you convert this image to 8 or 16 bits, Photoshop applies a tone-mapping algorithm using the values you select to take this extended-dynamic-range image and convert it into something you can see on the screen. Just as old versions of Photo- shop didn’t work well with 16-bit images, CS5 has limited tools for working with 32-bit images, which is why there aren’t many adjustments that you can apply to a 32-bit image. 7. We recommend you leave the next drop-down set at the default choice, Local Adaptation, which controls the tone-mapping algorithm. This offers the most control in a straightforward interface. 8. If something moved slightly from one exposure to the next, check Remove Ghosts; otherwise leave it unchecked. 9. We recommend beginning with the controls within the Tone and Detail section. Adobe has made the new interface a lot more user-friendly; hover your cursor over any of the sliders to see a tooltip explaining its function. The Gamma slider controls the overall contrast between the highlights and the shadows. To gain more contrast, move the slider to the left, and to decrease the contrast, move it to the right. We often find we need to adjust the Gamma slider a little to the left, but be mindful of losing highlight or shadow detail. Working in 32-Bit Mode Choose 32 - bit mode if you want to apply adjustments that work in 32 - bit space, such as Gamma and Exposure, as a layer. Note that if you choose 32 - bit, all the other options in the Merge to HDR Pro dialog disappear and you must press OK to continue, or change the mode back to 16 - bit. After applying adjustments as layers in 32 - bit mode, you must flatten the image in order for the adjustments to have their intended effect. Then go to Image Mode 16 - bit to convert the image back to 16 - bit space and continue with your workflow. If you don’t flatten the image before changing the bit depth, the adjustments will yield very unintended results. When you switch to 32 - bit mode, you’re creating a true HDR image with more data than can be displayed on the screen at once. When you convert this image to 8 or 16 bits, Photoshop applies a tone - mapping algorithm using the values you select to take this extended - dynamic - dynamic-dynamic range image and convert it into something you can see on the screen. Just as old versions of Photo - shop didn’t work well with 16 - bit images, CS5 has limited tools for working with 32 - bit images, which is why there aren’t many adjustments that you can apply to a 32 - bit image. Figure 8.10 Select your desired images in the Merge to HDR Pro dialog box. 4. Click OK. 5. This leads to a Merge to HDR Pro dialog box, shown in Figure 8.11. You can zoom in to see the results more closely, if desired, or uncheck one of the source images displayed on the bottom to exclude it from being part of the final image. The image preview automatically updates to reflect this change. Don’t worry if initially the image appears somewhat flat or too dark or too light. There are a lot of controls available so you can modify the results to suit your vision. 607343c08.indd 315 4/11/10 11:06:43 PM 316 c h a p t e r 8: COMPOSITES ■ 10. Use the Exposure slider to adjust the overall brightness of the image. To darken the image, move it to the left, and to lighten it, move the slider to the right. Again, keep an eye on your highlights and shadows as you adjust the Exposure. You can use the Curve tab to brighten or darken a smaller tonal range. 11. Adjust the Detail slider to emphasize or blur details in your image. In our expe- rience, some novices to HDR go overboard with this feature and tend to create images that look more like bizarre illustrations. This slider can be used creatively and wisely to enhance many images, whether to increase apparent detail or to blur it, but should not automatically be set to extremely high amounts. 12. Use the Shadow and Highlight sliders to lighten the shadow and highlight areas when pulled to the right, and darken them when moved to the left. 13. Use the Color tab to adjust both the Saturation and Vibrance sliders that oper- ate the same way they do in the Adjustments panel, except that they are applied directly to the merged image rather than as a layer. 14. You can create a curve using the Curve tab, which enables you to brighten or darken specific tonal ranges, as well as to increase or decrease the contrast within a segment of the tonal range just as the curve adjustment in the Adjustments panel does, but it too is applied directly to the merge. It has an additional feature in this interface, called Corner. When you select any point on the curve and then select Corner, the curve changes so that less of the tonal range is affected by the change to that point. In Figure 8.12 you can see that the curve becomes a series of line segments rather than a smooth curve. You must choose Corner for each point that you want to behave this way, and you can have some points that have Corner enabled, and others that don’t. We find Corner to be very helpful in protecting highlights. Figure 8.12 Checking the Corner option creates a dierent shape of curve that limits the tonal range that is aected. 15. We often adjust the Edge Glow sliders last. One of the things that many people particularly like about HDR images is the enhanced luminescence that they often seem to have. Use the Radius slider to increase (or decrease) the size of the glow, and the Strength slider to control the contrast within it. 16. When you are happy with the results, click OK and Photoshop will create a 16-bit merged image containing all your tweaks, as shown in Figure 8.13. But don’t forget that you can still apply any of the features in Photoshop to this image, just as you normally would. 607343c08.indd 316 4/11/10 11:06:43 PM 317 ■ EXPANDING DYNAMIC RANGE Figure 8.13 You can still use any of the regular features available in Photoshop on your HDR image. This image was ipped horizontally for a more pleasing composition. For Photoshop Elements Users: Creating HDR Images Elements has a much simpler interface for merging exposures and it provides a slightly different way to combine exposures. To begin the process of merging the images, select your images in Bridge and choose Tools > Photoshop Elements > Photomerge Exposure, or in Organizer choose File > New > Photomerge Exposure. Alternatively, open your files in Elements, select them in the Project Bin, and choose File > New > Photomerge Exposure. You will see the panel shown here: Continues Ph oto by Jo sh Ano n 607343c08.indd 317 4/11/10 11:06:45 PM 318 c h a p t e r 8: COMPOSITES ■ For Photoshop Elements Users: Creating HDR Images (Continued) Elements provides three levels of control over the process. Simple Blending provides no adjust- ment options, Smart Blending allows you to adjust highlight detail, shadows, and saturation, and Manual mode lets you composite the image yourself. We suggest that you start with Smart Blending to see if Elements will automatically combine your images reasonably. Note that if you used flash to capture your image, Elements will auto- matically start you in Manual mode. Adjust the sliders and see if you get good results. If you’re not satisfied, click the Manual tab. Manual mode works by starting with a background image and then adding regions from the other images. In Manual mode you draw on each exposure to indicate the regions that you want to use from that photo. For instance, if you’re photographing a bird at dusk, you might take one shot with flash exposed for the bird and another exposed for the background. Manual mode will let you easily combine the properly exposed bird with the properly exposed background. Follow these steps to use the Manual mode: 1. Select your background image and drag it to the area on the right marked Background. 2. Click a different photo in the Bin to load it into the source area. 3. Use the selection tool to draw strokes roughly over regions of the source photo that you wish to add on top of the background photo. Use the Eraser tool if you make a mistake. 4. Make sure to check Show Strokes so that you can see which areas you’ve selected. We rec- ommend toggling the Show Regions check box after each stroke so that you can see which parts of the composite image come from each source photo. We also recommend leaving Edge Blending checked so that the regions blend together as smoothly as possible. 5. Use the Transparency slider to adjust how much the source photo is blended into the final image. A higher transparency value means that the source image has less effect. 6. If Photoshop has trouble automatically aligning your images, use the Alignment tool to place three markers on each photo, giving Photoshop a hint about how to align them, and then press the Align Photos button. 607343c08.indd 318 4/11/10 11:06:46 PM 319 ■ E XPAN DIN G DY NAM IC R ANG E Single-Image HDR Photoshop CS5 has the ability to tone-map a single image to create effects similar to those resulting from Merge to HDR Pro. To begin, choose an image with a wide tonal range. Adjust it in ACR so that the image uses the entire tonal range but has no significant clipping. Click OK to open the image in Photoshop. You must open the image as an image, not a Smart Object, and it will work only if the image is flattened, so unfortunately this adjustment can be applied only directly to your Background layer. Note: Even though Single-Image HDR does not technically involve compositing, we’ve included it in this chapter since it’s a logical extension of HDR Pro. Go to Image > Adjustments > HDR Toning. A dialog will appear that is nearly identical to the Merge to HDR Pro interface. It may take a little bit before the image preview appears, because this is very processor-intensive. Adjust the sliders the same way, and click OK when you are happy with the results. As shown in Figure 8.14, this can be a very powerful way to add impact to an image! Figure 8.14 Using the new single-image tone-mapping feature is a great way to add impact to an image. HDR Images Using Third-Party Software Most of the time we rely on the tools within Photoshop to optimize our images and use additional software only when there is a clear benefit that justifies the expense. Photomatix software ( www.hdrsoft.com) offers stand-alone programs as well as plug-in versions of their HDR program that are excellent, as does Topaz Adjust ( www.topazlabs.com). They will work with Photoshop as well as Elements. You can sometimes get very different results by using a different program. So if you enjoy HDR imagery, we suggest you take a look at some of these programs. HDR Images Using Third-Party Software Most of the time we rely on the tools within Photoshop to optimize our images and use additional software only when there is a clear benefit that justifies the expense. Photomatix software ( www.hdrsoft.com ) offers stand - alone programs as well as plug - in versions of their HDR program that are excellent, as does Topaz Adjust ( www.topazlabs.com ). They will work with Photoshop as well as Elements. You can sometimes get very different results by using a different program. So if you enjoy HDR imagery, we suggest you take a look at some of these programs. 607343c08.indd 319 4/11/10 11:06:47 PM 320 c h a p t e r 8: COMPOSITES ■ Try It! Open the images from www.sybex.com/go/photoshopnature called HDR1, HDR2, and HDR3, and experiment with creating a 32-bit file and then converting it back to a 16-bit file. Extending the Depth of Field Nature photographers sometimes encounter situations where we want to maximize our depth of field (the range of apparently sharp focus within an image) but we encounter technical limitations. Perhaps the range we want to be in focus is too great for the lens, or the wind is blowing, so we have to use a relatively fast shutter speed to freeze the motion. Using the faster shutter speed may mean we can’t use as small an aperture as we’d like for a correct exposure without resorting to higher ISOs, which can lead to problems with noise. The solution is to take several shots with limited, but different, areas in focus and then combine them. Although you could opt to manually combine images by layering them and using layer masks, both Photoshop and Elements offer tools to automatically select the sharpest areas from each image and combine them into a single image. We’ll cover the Photoshop method first since it differs significantly from the Elements method. In Photoshop CS5 we’ll take advantage of a script to load the images into a sin- gle file and then have Photoshop automatically create the sharpest image possible by using advanced blending algorithms to choose the sharpest areas in a series of images and composite them automatically. It’s really quite impressive! To use this function, first take a series of shots with your camera on a tripod. Vary only the focus point. Begin at one extreme and slowly move the focus point back until the last area you want to be in focus is sharp. The more perfectly your images are aligned with no subject or camera movement, the better this method will work. Use your depth-of-field preview button, if you have one, to see what areas will be in focus and allow for overlap between the shots. Be careful to not change the exposure; only change the focus. 1. In Photoshop, choose File > Scripts > Load Files into Stack, or in Bridge select the images and choose Tools > Photoshop > Load Files into Photoshop Layers. Although you can opt to align the images in this step (and most of the time we do), you’ll have fewer alignment choices than if you wait and align then in a separate process, as described in Step 2. Do not choose the option to create a Smart Object, because you’ll need the layers intact. 2. If you did not align the layers in the previous step, select all layers and choose Edit > Auto-Align Layers > Auto or whichever method you prefer. 607343c08.indd 320 4/11/10 11:06:48 PM . change the focus. 1. In Photoshop, choose File > Scripts > Load Files into Stack, or in Bridge select the images and choose Tools > Photoshop > Load Files into Photoshop Layers. Although. access Merge to HDR Pro through Bridge directly or through Photoshop using these steps: 1. To select the files to use in Photoshop, choose File > Automate > Merge to HDR. The Merge to. the desired images, and choose Tools > Photoshop > Merge to HDR Pro. If you have opted to have Bridge auto-stack your HDR images, it will be even easier to choose the right files. Just