Adobe Photoshop CS5 for Photographers - Martin Evening [161]
However, you can also crudely adjust the color balance in Photoshop by using the Photo Filter adjustment, which is available in the Image Adjustments menu, or as an Adjustment panel option. The Photo Filter effectively applies a solid fill color layer with the blend mode set to ‘Color’, although you can achieve a variety of different effects by combining a Photo Filter adjustment with different layer blend modes. The Photo Filter offers a preset range of filter colors, but if you click on the Color button, you can select any color you like (after clicking on the color swatch) and adjust the Density to modify the filter's strength. Figure 5.54 shows a creative application for the Photo Filter adjustment.
Figure 5.54 The original version (left) had a strong orange cast. To modify this photograph, I added a Photo Filter adjustment. But instead of selecting a filter from the Filter presets list I clicked on the ‘Color’ swatch option (which opened the Color Picker dialog) and selected a deep blue color to filter the image with.
Multiple adjustment layers
Once you start adding multiple adjustment layers you can preview how an image will look using various combinations of adjustment layers and readjust the settings as many times as you want before applying them permanently to the photo. For example, you might want to use multiple adjustment layers to select different coloring treatments to a photo. Instead of producing three versions of an image, all you need to do is add three adjustment layers, each using a different coloring adjustment and switch the adjustment layer visibility on or off to access each of the color variations (Saving Layer Comps can help here).
Grouped adjustments
If you place your image adjustment layers inside a layer group you can use the layer group visibility to turn multiple image adjustments on or off at once (see Figure 5.55). You can also add a layer mask to a layer group and use this to selectively hide or reveal all the image adjustment layers contained within the layer group.
Figure 5.55 This shows an example of how adjustments can be grouped together and a single mask applied to the combined group of layers.
While it is possible to keep adding more adjustment layers to an image, you should try to avoid any unnecessary duplication of the layers. It is wrong to assume that when the image is flattened the cumulative adjustments somehow merge to become a single image adjustment. When you merge down a series of adjustment layers, Photoshop applies them sequentially, the same as if you had made a series of normal image adjustments. So the main thing to watch out for is any doubling up of the adjustment layers. If you find you have a Curves adjustment layer above a Levels adjustment layer, it would probably be better to try and combine the Levels adjustment within the Curves adjustment instead. Of course, when you use masked adjustment layers to adjust specific areas of a picture you can easily end up with lots of adjustment layers. One potential drawback of this is that it may slow down the screen preview times. This slowness is not a RAM memory issue, but to do with the extra calculations that are required to redraw the pixels on the screen. If you think this might be happening then try switching off some of the adjustment layers while you are editing the photograph.
To summarize, the chief advantages of adjustment layers are: the ability to defer image adjustment processing and the ability to edit the layers and make selective image adjustments. It is important to stress here that the pixel data in an image can easily become degraded through repeated image adjustments. Pixel data information will progressively become lost through successive adjustments as the pixel values are rounded off. This is one reason why it is better to use