Photoshop cs5 cho nhiếp ảnh gia part 18 potx

Using the Basic Tab whether or not you choose to use the Auto settings as your default, chances are that you will often want to make some tonal and color adjustments to your images.. The

For Photoshop Elements Users: Custom Defaults

Elements does not support saving or loading settings, but it does allow you to save new Camera Raw defaults

To save your settings as the new default for ACr to use for all images (before they are individually adjusted), adjust the sliders and settings as desired, and then

choose save new Camera raw defaults You will not see a dialog box asking which

settings to save—it saves all of them if you later change your mind, you can click

reset Camera raw defaults

Using the Basic Tab

whether or not you choose to use the Auto settings as your default, chances are that

you will often want to make some tonal and color adjustments to your images The

ability to easily make subtle tweaks, as well as major corrections, to your exposure is

one of the many advantages of working with the ACr interface

The basic tab icon is visible by default when the ACr interface first opens; it contains the white balance adjustments as well as some exposure and color adjustments

Setting White Balance

one of the major advantages of using the ACr interface is the ability to fine-tune

the white balance, or color cast if you decide that you want to make your picture as

neutral as possible, then including a gray card such as the whibal card (available at

www.rawworkflow.com) or the new spyderCube (www.datacolor.com) within one frame of

your pictures makes it easy to determine the correct white balance Just use the white

balance tool and click the gray tone in the card or cube in your image in fact, you

can use this eyedropper to click any pixel within any image that you want to define as

neutral—that is to say, any shade of pure gray from the lightest to the darkest gray—

and the tonalities within the entire image are remapped accordingly

however, for most nature photographers pure neutral is not the goal for most images we nature photographers tend to like the warm color casts of early morning

and late daylight sometimes we even like the cool colors of shadows and/or the harsh

blue light on winter snow And sometimes we like to pretend those color casts were

present even when they weren’t! in such cases, the white balance you ultimately select

may be correct, but perhaps not accurate Fortunately, there are no “white-balance

police” running around demanding that your choice of white balance must be true to

life! however, if you’re trying to depict your images more documentarily, then you’ll

want to make your white-balance choices as accurate as possible

Note: There is a difference between accurate white balance and correct white balance Accurate white balance portrays the lighting as it existed when you photographed the scene Correct white bal-ance is the ideal setting that gives the image the feeling you seek to express

For Photoshop Elements Users: Custom Defaults

Elements does not support saving or loading settings, but it does allow you to save new Camera Raw defaults

The basic tab has two sliders that control the white balance or color cast of your image:

T

• he Temperature slider refers to the temperature of the light (in degrees Kelvin)

what you really need to know is that moving the slider to the left adds a blue cast to your image, similar to using an 80 A, b, or C filter moving the Temper-ature slider to the right adds a warm yellow cast, similar to using an 81 A, b, or

C filter There’s a blue/yellow gradient associated with the Temperature slider, making it obvious which direction to move the slider

T

• he Tint slider controls the green/magenta color cast moving this slider to the left increases the greenish cast; moving it to the right increases the magenta cast

we find that we tend to adjust the Tint slider less than the Temperature slider in general

The major advantage the white-balance sliders have over using a filter is that the adjustments are continual and gradual, so you can choose the precise amount of warming or cooling to apply to convey the mood you have in mind

Unless you are color-blind (and we’re being serious here, not sarcastic, having had several color-blind students), it’s well worth getting into the habit of spending a lit-tle time adjusting the white balance because the changes you can make to the colors of your image here are subtly different from what you can do within Photoshop (see Fig-ure 3.10) And if you are color-blind, you may want to get into the habit of setting the cursor on a specific point in the image and noting the rgb values that appear above the histogram You can learn to interpret the values so you know when your image is slightly warm or cool (we talk more about this in Chapter 7, “Color Adjustments.”)

Figure 3.10 Adjusting the Temperature and Tint sliders allows you to make finer adjustments to the color cast in your

image than would be possible using traditional filters

Adjusting Tonalities

The next group of sliders on the ACr basic tab enables you to fine-tune the

tonali-ties in your image, such as increasing or decreasing the exposure, contrast, and so on

we’ll describe the sliders in the order that we usually set them

Note: Although we usually follow a certain order adjusting these sliders, if one aspect of an image is significantly off, we’ll adjust that first Since you can readjust these sliders as much as neces-sary, you can set them in whatever order seems most logical to you

Setting the Exposure and Blacks Sliders

Using the exposure slider is similar to using Levels in Photoshop to set your white

point in plain english, this means you are selecting which tonal value (pure white,

almost but not quite pure white, and so on) to make the lightest pixels within your

image, and all pixels in the image are remapped accordingly in many ways it’s

simi-lar to modifying your in-camera exposure, but instead of being limited to a half or

a third of a stop, or multiples thereof, you can choose from continuous values using

tiny increments, up to four stops over or under the in-camera exposure however,

remember that if you overexposed your image in-camera to the point that no details

were captured in the brightest highlights, using the exposure slider does not restore

the details ACr cannot produce detail that was never captured in either highlight or

shadow areas however, it may make those blown-out areas a little less obvious by

making them a light shade of gray instead of bright white

Note: To quickly reset any of the sliders in ACR to their default values, double-click the small triangle that specifies the value on the slider It will automatically return to its default setting

Use the blacks slider to set the black point You are telling ACr how close to pure black you want the darkest pixels within your image to be simply drag the slider

to the desired value Usually you won’t have to drag the slider far, because you’re

work-ing on the linear-gamma data—that is, preconverted information

To set your exposure and blacks sliders without accidentally clipping any pix-els, do the following:

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• old down the Alt/option key, and drag the exposure slider; the preview box

turns completely black drag the slider to the right (or left) until you see a few colored pixels appear These are the first pixels that start to become pure white with no detail reduce the exposure slightly so there is no clipping, and release the mouse button

h

• old down the Alt/option key while sliding the blacks slider to set the black

point with no clipping with the blacks slider, the preview becomes totally white when you see colored pixels begin to appear, back off slightly by doing

this, you have distributed the pixels in your image over the maximum tonal range using clipping previews

Although you could just rely on the clipping warnings in the preview, holding down the Alt/option key makes it easier to see clipping in small areas

it’s tempting for some photographers to assume that all pictures should have

as wide a range of tonal values as possible indeed, many images look their best uti-lizing the full range of tonal values—which is what you’re doing if you set the white and black points using the exposure and blacks sliders while utilizing the clipping previews however, especially within nature photography, not all images are suited

to using the full range of tonal values For example, if you take a moody picture of

a lovely foggy scene, as shown in Figure 3.11, you most assuredly don’t want maxi-mum contrast You want a limited tonal range reflecting the limited tonalities visible through the fog You need to look at each image and decide whether it should utilize the full range of tonalities

Figure 3.11 Some pictures, like this foggy scene, must not use the full range of tonal values Note that the histogram does not

extend all the way to each end but rather is limited to more of the middle and light tonalities

Using the Recovery and Fill Light Sliders

The recovery and Fill Light sliders, which are similar to the highlight/shadow tool in Photoshop, are extremely useful when, despite your best efforts, there is some clipping

of the highlight and/or shadow values because of contrasty lighting You can use the recovery slider to recapture as much highlight detail as possible, while the Fill Light slider recovers shadow detail, as shown in Figure 3.12

Figure 3.12 The Recovery and Fill Light sliders can help expand the exposure latitude of an image so you can see detail in the

highlights and shadows in contrasty scenes

The best approach is to first set the exposure slider so that the exposure is cor-rect for most of the image Then adjust the recovery slider as necessary to regain as

much highlight detail as possible

Note: If you overexposed or underexposed the image to the point that you didn’t capture some of the highlight or shadow data, the Recovery and Fill Light sliders will not be able to recover it It can’t create infor-mation that you didn’t capture But if you were able to capture it on the sensor, then the Recovery slider will reveal it Remember that the sensor contains more information than can be displayed initially—usually up

to about 1/2 stop more information in the highlights and up to 11/2 stops more information in the shadows

set the Fill Light slider as necessary to recover detail in the darkest shadow areas You may need to modify the blacks slider setting as well The trick is that you still want some true blacks in your image, but you want to see detail in the not-quite-black shadow areas

Using the Brightness and Contrast Sliders

The brightness slider shifts the majority of the pixels lighter or darker to make the overall image appear lighter or darker watch how the bulk of the histogram shifts as you move this slider each way it’s similar to moving the center slider within Levels in Photoshop

The more extreme the adjustments you make with the exposure slider, the more likely it

is you’ll need to make adjustments using the brightness slider don’t forget to keep an eye out for any clipping you may introduce by increasing or decreasing the brightness

The Contrast slider is similar to applying an s curve within Curves in Photo-shop to increase or decrease the contrast within the bulk of the pixel values if you watch the histogram as you adjust this slider, you’ll see the bulk of the pixels being shifted away from the middle toward the extremes

Contrast is primarily modified in those pixels in the middle tonalities, with the lightest and darkest tonalities being less affected increasing the amount to greater than the default of +25 lightens values above the midtones and darkens values below the mid-tones similarly, reducing the value darkens values above the midtones and lightens values below the midtones to reduce the overall contrast if you decide to adjust the contrast in ACr, be sure to check that you have not introduced any clipping to your highlights or shadows You may have to readjust the other sliders

Note: Given the ability to make some fairly dramatic changes in exposure, it may seem as if you don’t have to worry about capturing the correct exposure in-camera In fact, as discussed in Chapter 1,

“Thinking Digitally,” the better your initial exposure, the better the final product will be If the image is initially underexposed, you’ll find that although you can correct the exposure, there is likely to be a lot

of distracting noise in the final image If you “expose to the right” (again, see Chapter 1), you will have the least amount of noise within your image, although you may have to adjust the Blacks slider, and possibly the Brightness slider as well Exposing to the right with raw captures ultimately gives you the best possible result as long as you make certain you don’t clip the highlights

Modifying Clarity, Vibrance, and Saturation

The Clarity slider is sometimes called the “make-it-better” slider, and we use it on most

of our images when the slider is adjusted to the right, it increases midtone contrast