Adobe Photoshop CS3 for Photographers phần 4 pps

Martin Evening Adobe Photoshop CS3 for Photographers 176 Correcting shadow and highlight detail The Shadow/Highlight image adjustment enables you to reveal more detail in either the shadow or highlight areas of a picture. Shadow/Highlight is a great image adjustment tool to use whenever you have useful tonal information but it is just too compressed to be seen properly. It can be used to perform wonders on most images, not just those that desperately require corrections to recover detail in the shadows and highlights. The Shadow/Highlight image adjustment tool makes adaptive adjustments to an image, and it works much in the same way as our eyes do when they automatically compensate and adjust to the amount of light illuminating a subject. The Shadow/Highlight adjustment works by looking at the neighboring pixels in an image and making a compensating adjustment based on the average pixel values within a given radius. In Advanced mode, the Shadow/ Highlight dialog has various controls which allow you to make the following fi ne-tuning adjustments. Amount This is an easy one to get to get to grips with. The default Amount setting is 50%. Increase or decrease this to achieve the desired amount of highlight or shadow correction. I fi nd this default setting does tend to be rather annoying, so I usually try setting the slider to a lower amount or zero and click on the Save As Defaults button to set this as the new default setting for every time I open Shadow/Highlight. Tonal Width The Tonal Width determines the tonal range of pixel values that will be affected by the Amount set. A low Tonal Width setting will narrow the adjustment to the darkest or lightest pixels only. As the Tonal Width is increased the adjustment will spread to affect more of the midtone pixels as well. Figure 4.34 The Shadow/Highlight adjustment dialog shown here in basic mode. Checking the Show More Options box will reveal the Advanced mode dialog shown below in Figure 4.35. Figure 4.35 The Show More Options mode Shadow/Highlight dialog contains a comprehensive range of controls. I would advise you to always leave this box checked. chapter_04.indd 176chapter_04.indd 176 5/2/07 2:38:13 PM5/2/07 2:38:13 PM 177 Basic pixel image editing Chapter 4 Radius The Radius setting basically governs the pixel width of the area that is analyzed when making an adaptive correction. Let’s concentrate on what would happen when making a shadow correction. If the Shadow Radius is set to zero, the result will be a very fl at-looking image. You can increase the Amount to lighten the shadows and restrict the Tonal Width, but if the Radius is low or is set to zero, Photoshop will have very little ‘neighbor pixel’ information to work with when trying to calculate the average luminance of the neighboring pixels. So if the sample Radius is too small, the midtones will also become lightened. If the Radius setting is set too high, this will have the effect of averaging all of the pixels in the image and likewise the lightening effect will be distributed such that all the pixels will get the lightening treatment, not just the dark pixels. The optimum setting to use is dependent on the image content and the area size of the dark or light pixels. The optimum pixel Radius width should be about half that amount or less. In practice you don’t have to measure the pixel width of the light and dark in every image to work this out. Just be aware that after you have established the Amount and Tonal Width settings, you should adjust the Radius setting making it larger or smaller according to how large the dark or light areas are. There will be a ‘sweet spot’ where the Shadow/Highlight correction is just right. Figure 4.36 The Tonal Width slider determines the range of levels the Shadow/ Highlight adjustment is applied to. So, for example, if the Shadow adjustment Tonal Range is set to 50, then the pixels which fall within the darkest range from level 0 to level 50 will be adjusted. Radius halos As you make an adjustment to the Radius setting you will sometimes notice a soft halo appear around sharp areas of contrast between dark and light areas. This is a natural consequence of the Radius function and is most noticeable when you are making dynamic changes to the image. Aim for a Radius setting where the halo is least noticeable or apply a Fade adjustment after applying the Shadow/Highlight adjustment. If I am really concerned about reducing halos, I sometimes use the history brush to selectively paint in a Shadow/Highlight adjustment. chapter_04.indd 177chapter_04.indd 177 5/2/07 2:38:15 PM5/2/07 2:38:15 PM Martin Evening Adobe Photoshop CS3 for Photographers 178 1 In this photograph of young Lillian, her face is quite dark because she is backlit by the sun. But with a little help from the Shadow/Highlight adjustment, I can bring out more detail in her face and darken the sky. 2 I went to the Image menu and chose Adjustments ➯ Shadow/ Highlight. I set the Amount to 36% and raised the Tonal Width to 60%. The Radius adjustment is now crucial because this determines the distribution width of the Shadow/Highlight adjustment. As you can see in this step, if I set the Radius to zero, the result will look incredibly fl at. 3 The other alternative is to take the Radius setting up really high. But this too can diminish the Shadow/Highlight adjustment effect. The simple way to approach setting the Radius is to realize that the optimum setting is area size related and it will fall somewhere midway between these two extremes. In the end, I went for a high Radius setting of 124 pixels for the shadows and 165 pixels for the highlights. This was because I was correcting large shadow and large highlight areas and these settings appeared to provide the optimum correction for this particular photograph. chapter_04.indd 178chapter_04.indd 178 5/2/07 2:38:16 PM5/2/07 2:38:16 PM 179 Basic pixel image editing Chapter 4 Color Correction As you correct the highlights and the shadows, the color saturation may unexpectedly change. This can be a consequence of using the Shadow/Highlight to make extreme adjustments. The Color Correction slider will let you compensate for any undesired color shifts. Midtone Contrast Even though you may have paid careful attention to getting all the above settings optimized just right so that you target only the shadows or highlights (or both), the midtone areas may still get affected and you can lose some contrast. The Midtone Contrast slider control lets you restore or add more contrast to the midtone areas. CMYK Shadow/Highlight adjustments You may notice that the Shadow/Highlight adjustment performance is improved and you can now use Shadow/Highlight in CMYK color as well. Adobe Camera Raw adjustments Shadow/Highlight can work great on a lot of images, but now that Camera Raw can be used to edit JPEG and TIFF images as well as raw fi les, you may like to explore using the Recovery and Fill Light adjustments described on pages 258–259. In many cases you will fi nd that Recovery and Fill Light work better. chapter_04.indd 179chapter_04.indd 179 5/2/07 2:38:18 PM5/2/07 2:38:18 PM Martin Evening Adobe Photoshop CS3 for Photographers 180 Smart Filters This is perhaps a good time to introduce the Smart Filters feature in Photoshop CS3, which will allow you to apply most fi lter adjustments non-destructively. And as shown here, also apply a Shadow/Highlight adjustment non- destructively. In the following steps I have provided a brief introduction to working with Smart Filters. Smart Filters are essentially fi lter effects that are applied to a Smart Object, and the process always starts with you converting a layer or group of layers to a Smart Object, or selecting a layer and choosing Convert for Smart Filters. 1 To apply a Shadow/Highlight adjustment as a non-destructive smart fi lter, the Background layer (or a group of layers) must fi rst be converted to a Smart Object. To do this I went to the Filter menu and chose: Convert for Smart Filters. This converted the Background layer to a normal, Layer 0 layer. Pros and cons of Smart Filters The appeal of Smart Filters is that you can apply any fi lter non-destructively to an image in Photoshop. But this fl exibility comes at the cost of larger fi le sizes (4 to 5 times bigger), a slower workfl ow switching between the Smart Object and parent documents and longer save times, at least this has been my experience when working with a fairly fast computer with lots of RAM memory. But this is not the fi rst time we have come across speed problems like this: some Photoshop techniques are a little ahead of themselves and we have to wait for the computer hardware to become faster before we can use them comfortably. While Smart Filtering does offer true non-destructive fi ltering, it is a technique you probably want to use sparingly. In this book I have highlighted a few of the situations where Smart Filters may offer some benefi t, such as when blurring a background layer, or using the midtone contrast technique shown on pages 184–185. chapter_04.indd 180chapter_04.indd 180 5/2/07 2:38:20 PM5/2/07 2:38:20 PM 181 Basic pixel image editing Chapter 4 2 I then went to the Image menu and chose Adjustments ➯ Shadows/Highlight and applied the settings shown here. As you can see, I used the Shadows/Highlight adjustment to bring out more detail in the shadows. If you check the Layers palette you will notice that the Shadows/Highlight adjustment has added a Smart Filter layer to the layer stack. You can now click the eye icon to switch the effect on or off. And when I double-clicked on the Smart Filter blend options button (circled), this opened the Blend Options dialog shown here, which allowed me to adjust the opacity of the Smart Filter adjustment. chapter_04.indd 181chapter_04.indd 181 5/2/07 2:38:22 PM5/2/07 2:38:22 PM Martin Evening Adobe Photoshop CS3 for Photographers 182 3 I was then able to double-click on the Smart Object icon in the Layers palette and open the Smart Object layer in a new document window. This image document is the original image without the Shadow/Highlight adjustment and I could now edit this document as one would do normally. If you look at the Layer palette for the Smart Object you will notice that I added a Curves adjustment layer to apply some localized lightening to the center of the image and a second adjustment layer to apply a darkening vignette to the edges of the photograph and, fi nally, a Black & White adjustment layer to convert the image to monochrome. That pretty much completed all the work I wanted to carry out on the Smart Object. When I closed the document window a dialog box prompted me to save it, which you must do in order to save the Smart Object adjustments back to the parent document. chapter_04.indd 182chapter_04.indd 182 5/2/07 2:38:26 PM5/2/07 2:38:26 PM 183 Basic pixel image editing Chapter 4 Improving the midtone contrast The technique described over the next few pages was shown to me by Jeff Schewe (who also shot the Antarctica pictures I used here), and Jeff in turn has credited Mac Holbert of Nash Editions as the person who actually devised this really clever way of improving the midtone contrast in a photograph. The technique relies on the use of the High Pass fi lter applied using the Overlay blend mode, to add halo edges specifi cally to the midtone areas of the picture. This is really a kind of soft edge, midtone sharpening technique and it is particularly useful when applied to subjects like landscapes, and can be used to help bring out more detail when making a print. Figure 4.37 The photograph shown here nicely illustrates the benefi ts of the midtone contrast technique described over the next few pages. The left half shows the before version and the right half how the image detail looks so much sharper and more contrasty in the midtone areas. Photograph: Jeff Schewe. Nash Editions Nash Editions is based in California, and was founded in 1990 by Mac Holbert and Graham Nash to provide a specialist fi ne- art digital printing service. They were the original pioneers of fi ne-art inkjet printing. chapter_04.indd 183chapter_04.indd 183 5/2/07 2:38:36 PM5/2/07 2:38:36 PM Martin Evening Adobe Photoshop CS3 for Photographers 184 1 In this example I wanted to demonstrate how the medium contrast technique could be applied to a photograph using a Smart Filter technique. You are not supposed to have to duplicate the Background layer in order to use Smart Filter layers, but in this instance it was necessary because the Smart Filter blending options are not yet as comprehensive as one would like. I began by dragging the Background layer to the New Layer button to make a copy and went to the Filter menu and chose: Convert for Smart Filters. 2 With the Background copy layer selected (which is now a Smart Object), I went to the Filter menu and chose Other ➯ High Pass. It does not matter too much at this stage what value is used since I was able to re-edit this setting later at Step 4. Photograph: Jeff Schewe. chapter_04.indd 184chapter_04.indd 184 5/2/07 2:38:38 PM5/2/07 2:38:38 PM 185 Basic pixel image editing Chapter 4 3 Now that I had applied the High Pass fi lter, I needed to change the layer blend mode setting to Overlay. To do this I double-clicked on the Background copy layer, targeting the blank space area (this is the area within the green box and not the thumbnail or the layer name itself). I set the blend mode to Overlay and at the same time, went to the Blend If options at the bottom and adjusted the This Layer sliders so that they were split as shown above: 50/100 150/200. To set the sliders like this, you have to hold down the OA key to split them apart. 4 The layer blend changes will cause the fi lter layer to blend with the layer below, adding a radius halo around the midtone areas of the photograph only. It is at this fi nal stage that you might want to double-click the High Pass fi lter layer in the Layers palette (circled) to reopen the Filter dialog and fi ne-tune the fi lter setting. chapter_04.indd 185chapter_04.indd 185 5/2/07 2:38:45 PM5/2/07 2:38:45 PM [...]... selection and clicked on the Add Layer Mask button (circled) in the Layers palette to convert this active selection into a layer mask for the Background copy layer 191 chapter_ 04. indd 191 5/2/07 2:38:59 PM Martin Evening Adobe Photoshop CS3 for Photographers 4 The mask was now ready for editing I went to the Filter ➯ Stylize menu and chose Find Edges This was then followed by a Gaussian Blur filter of between... Inkjet printing/halftone conversion Figure 4. 41 The above diagram maps out the path to blurry destruction for photons that enter a camera lens and are eventually interpreted as printer’s ink on the page At each of the above stages either a little or a lot of detail will become lost 195 chapter_ 04. indd 195 5/2/07 2:39:12 PM Martin Evening Adobe Photoshop CS3 for Photographers Halftone conversion Pixel... to the new merged copy layer 209 chapter_ 04. indd 209 5/2/07 2:39 :41 PM Martin Evening Adobe Photoshop CS3 for Photographers 3 With this new blurred layer selected, I then chose Image ➯ Calculations and used the same settings as before But note that the Layer section should point to this new blurred layer: Layer 1 I clicked OK to create a new alpha channel 4 The following steps all take place on the... to 10 solved the problem The photograph was made to appear sharper but without sharpening too much of the film grain Photograph by Eric Richmond 201 chapter_ 04. indd 201 5/2/07 2:39:21 PM Martin Evening Adobe Photoshop CS3 for Photographers Figure 4. 46 Unsharp masking can produce chromatic artifacts in some areas of the image Luminance sharpening can help when you want to avoid overemphasizing the color... I was presharpening an image with softer edges, I might apply a larger Radius Blur This was followed by applying the Levels adjustment shown here 207 chapter_ 04. indd 207 5/2/07 2:39: 34 PM Martin Evening Adobe Photoshop CS3 for Photographers 5 For the next step, I dragged the Alpha 1 channel down to the Make Selection button to load as a selection and then clicked on the Add layer mask button in the... Blue channel is usually the noisiest so it can therefore be a good idea to apply more reduction to this channel and less to the Red and Green channels where the noise is not such a major problem Figure 4. 39 A close-up view of the Reduce Noise filter settings in Advanced mode 189 chapter_ 04. indd 189 5/2/07 2:38:56 PM Martin Evening Adobe Photoshop CS3 for Photographers Record as an action To save repeating... losses will occur when outputting the image as a halftone print or inkjet Further sharpening in Photoshop is therefore recommended before you make any type of output 196 chapter_ 04. indd 196 5/2/07 2:39: 14 PM Chapter 4 Basic pixel image editing Sharpening solutions Over the years various strategies have evolved For example, some film scanning devices are set up to automatically sharpen scanned images so... applied to a copy layer, you have the ability to fade the opacity of the layer or mask the layer contents to restore more of the original version of the image 187 chapter_ 04. indd 187 5/2/07 2:38 :49 PM Martin Evening Adobe Photoshop CS3 for Photographers Reduce Noise filter The Reduce Noise filter uses a method of smart noise reduction that can remove noise from an image without destroying the edge detail in... routine and adapt the Unsharp Mask settings at the end to suit your needs and visually check to see if the image looks sharp enough on the screen 205 chapter_ 04. indd 205 5/2/07 2:39:31 PM Martin Evening Adobe Photoshop CS3 for Photographers Sharpening for fine to moderate edges This next stage takes the presharpening process one stage further and shows you how to additionally presharpen an image where the... Color and applied the Gaussian Blur filter to this layer For this particular image a blur radius of 12 pixels was required to eradicate the moiré Note that when you use a Color blending mode, it is only color information that is blurred – the luminosity (the detail information) will remain unaffected 1 94 chapter_ 04. indd 1 94 5/2/07 2:39:09 PM Chapter 4 Basic pixel image editing Image sharpening It is an . mask for the Background copy layer. chapter_ 04. indd 191chapter_ 04. indd 191 5/2/07 2:38:59 PM5/2/07 2:38:59 PM Martin Evening Adobe Photoshop CS3 for Photographers 192 4 The mask was now ready for. the original version of the image. chapter_ 04. indd 187chapter_ 04. indd 187 5/2/07 2:38 :49 PM5/2/07 2:38 :49 PM Martin Evening Adobe Photoshop CS3 for Photographers 188 Reduce Noise fi lter The Reduce. and fi ne-tune the fi lter setting. chapter_ 04. indd 185chapter_ 04. indd 185 5/2/07 2:38 :45 PM5/2/07 2:38 :45 PM Martin Evening Adobe Photoshop CS3 for Photographers 186 Removing noise from an image This