6.14. Straightening

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6.13. Color Balance

If all you ever shoot is black-and-white photos, then Exposure/Levels or Brightness/ Contrast may be all you ever need. If you're like most people, though, you're also concerned about a little thing called color.

One of the most common failings of digital cameras (and scanners , too) is that they don't capture color very accurately. Digital photos sometimes have a slightly bluish or greenish tinge, producing dull colors, lower contrast, and sickly looking skin tones.

FREQUENTLY ASKED QUESTION
Battle of the Sliders

All right, first you said that I can create a well-balanced histogram with the Exposure and Levels sliders. Then you said that the Brightness and Contrast sliders do pretty much the same thing. So which should I use?

Photography forums everywhere are overflowing with passionate comments advocating one approach over the other.

The bottom line is, for most normal JPEG photos, you can use whichever you prefer, as long as you wind up creating a histogram whose peaks generally span the entire graph.

If you have no preference, you may as well get into the habit of using the Exposure and Levels sliders. One day, when you begin editing super- high-quality RAW files (page 91), you'll appreciate the clever way these controls interpret the data from the camera's sensors with virtually no loss of quality.


In fact, the whole thing might have a faint green or magenta cast. Or maybe you just want to take color adjustment into your own hands, not only to get the colors right, but to also create a specific mood for an image. Maybe you want a snowy landscape to look icy blue so friends back home realize just how darned cold it was!

The Adjust panel offers three sliders that wield power over this sort of thing: Tint, Temperature, and Saturation. And it offers two ways to apply such changes: the manual way and the automatic way.

6.13.1. Manual Color Adjustment

These three sliders in the middle of the Adjust Palette provide you with plenty of color adjustment power. In particular, the Tint and Temperature sliders govern the white balance of your photo. (Different kinds of lightfluorescent lighting, overcast skies, and so onlend different color casts to photographs. White balance is a setting that eliminates or adjusts the color cast according to the lighting.)

For best results, start at the bottom slider and work your way upward.

  • Tint. If you've ever fiddled with the tint control on a color TV, you already have a decent idea how this slider works. It adjusts the photo's overall tint along the red-green spectrum. Nudge the slider to the right to add a greenish tint, left to add red. As you go, watch the histogram to see how iPhoto is applying the color.

    Adjusting this slider is particularly helpful for correcting skin tones and compensating for difficult lighting situations, like pictures you took under fluorescent lighting. (See Figure 6-10.)

  • Temperature. This slider, on the other hand, adjusts the photo along the blueorange spectrum. Move the slider to the left to make the image " cooler ," or slightly bluish. Move the slider to the right to warm up the tones, making them more orangisha particular handy technique for breathing life back into subjects that have been bleached white with a flash. A few notches to the right on the Temperature slider, and their skin tones look healthy once again!

    POWER USERS' CLINIC
    Coping with Fluorescent Lighting

    You can correct most pictures using the automatic graybalance feature or the Tint, Temperature, and Saturation sliders described in this chapter. Some images, however, will frustrate youno amount of tweaking will seem to make their colors look realistic. Pictures taken under fluorescent lighting can be particularly troublesome .

    The problem with fluorescent bulbs is that they don't produce light across the entire color spectrum; there are, in effect, spectrum gaps in its radiance. Your best colorcorrection tool, the Temperature slider, only works on images where a full spectrum of light was captured, so it doesn't work well on fluorescently lit shots.

    You'll have some luck moving the Tint slider to the left to remove the green cast of fluorescent lighting. But the overall color balance still won't be as pleasing as with pictures shot under full spectrum lighting, such as outside on a sunny day.

    The best time to fix fluorescent-light color-balance problems, therefore, is at the moment you take the picture. Use the camera's flash, ensuring that it's the dominant light source, where possible. Its light helps to fill in the gaps in the fluorescent spectrum, making color correction much easier in iPhoto later.


    Professional photographers love having color-temperature control; in fact, many photographers could handle the bulk of their image correction with nothing but the Exposure and Temperature controls.

    Figure 6-10. Moving the Tint slider just a little to the right removed a little red. Nudging the Temperature slider to the right warmed up the colors, making the grass more appealing. To make the colors more vibrant, move the Saturation slider to the rightnot too far, unless you're after a Mars-like, otherworldly effect.


  • Saturation. Once you're happy with the color tones, you can increase or decrease their intensity with the Saturation slider. Move it to the right to increase the intensity and to the left for less saturation.

    When you increase the saturation of a photo's colors, you make them more vivid ; essentially , you make them "pop" more. You can also improve photos that have harsh , garish colors by dialing down the saturation, so that the colors end up looking a little less intense than they appeared in the original snapshot. That's a useful trick in photos whose composition is so strong that the colors are almost distracting.

    (iPhoto's Enhance button automatically adjusts saturation when "enhancing" your photos, but provides no way to control the degree of its adjustment.)

6.13.2. Automatic Color Correction

Dragging the Tint, Temperature, and Saturation sliders by hand is one way to address color imbalances in a picture. But there's an easier way: iPhoto also contains a fairly secret feature that adjusts all three sliders automatically.

Technically, this tool is a gray balance adjuster. It relies on your ability to find, somewhere in your photo, an area of what should appear as medium gray. If you can adjust the color balance so that this spot does in fact appear the correct shade of gray, iPhoto can take it from thereit can adjust all of the other colors in the photo accordingly , shifting color temperature, tint, and saturation, all with a single click. This trick works amazingly well on some photos.

Before you use this feature, though, make sure you've already adjusted the overall exposure of the photo, using the steps described on the previous pages.

Next, scan your photo for an area that should appear as a neutral gray. Slightly dark grays are better for this purpose than bright, overexposed grays. (See Figure 6-11.)

Once you've found such a spot, -click it.

Figure 6-11. Indoor settings often present tricky lighting situations. Here, this existing light shot has a greenish cast to it.
Bottom: By -clicking a gray midtone spotin this case, the case of the inkjet printer on the desk (see the cursor?), you tell iPhoto, "This is supposed to be gray. Use this information to correct all the other colors appropriately."
If you don't like iPhoto's correction, choose Edit Undo and try again on a different gray area.


Instantly, iPhoto automatically adjusts the color-balance sliders to balance the overall color of the photo. If you don't like iPhoto's correction, choose Edit. Undo and try again on a different gray area.

Thankfully, there's a good way to check how well iPhoto corrected the image. Find a spot in the picture that should be plain white. If it's clean (no green or magenta tint), you're probably in good shape; if not, undo the gray balance adjustment and try again on another area of gray.


Tip: If you're a portrait photographer, you can use the gray-balance control to correct skin tones with almost magical efficiency. The trick is to plan ahead by stashing a photographer's gray card somewhere in the composition (somewhere that can be cropped out of the final print). Make sure the gray card receives about the same amount of lighting as the subject.Later, when you're adjusting the image in iPhoto, you can -click the gray card in the composition, and presto: perfect skin tones. Now crop out the gray card and make your print, grateful for the time you've just saved.
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iPhoto 5. The Missing Manual
iPhoto 5. The Missing Manual
ISBN: 596100345
EAN: N/A
Year: 2005
Pages: 179

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