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TUTORIAL 3Adobe Photoshop

Overall Color, Contrast and Sharpness Adjustments

Figure 44Analyzing the Image: The first thing to do when determining how to process an image is to developa strategy based on the intended use. When you know what you plan to do with the image the nextstep is to look at the image and determine how to get the image ready for that intended use.


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COLOR CORRECTION WITH PHOTOSHOP

This tutorial will take you through these steps using the examplephotograph, Barn and Pond, Figure .The Evaluation of this imageindicates that the image is:1- De-saturated (Lacks Purity of Color)2- Flat (Lacks Contrast)3- Slightly Magenta (Has a Color Cast)

The next tutorials using the Photoshop Color Correction Tools willcorrect each of these flaws.

Step 1. MAKE A COPY OF THE ORIGINAL FILEAlways make a copy of your original file before making changes.Select File>Save As and rename your file. Save it as a PSD.

Step 2. CREATE ADJUSTMENT LAYER

Making changes on an Adjustment Layer method does not change thedata of the file. It preserves the original data and the corrections aredone in layers and can be undone easily.

When making changes, it is possible to evaluate different methods bytoggling back and forth between Adjustment Layers. This is done bycreating a new Adjustment Layer for each change. The down side isthat this method adds data to the file which increases the file size andmemory requirements.To Make and Adjustment Layer:

Figure 45.

Pull Down Layer Menu, Select New Adjustment Layer

For this Exercise Choose Levels

NOTE: Be sure the Preview Button is Selected in the Dialogue Box soyou can see the changes.

Figure. 45Creating a new Ad justment Layer.


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Step 3. LEVELS AUTO ADJUSTMENTTo the Right is the dialogue box for Levels Adjustments. It contains aHistogram, which indicates the amount of data related to RGB andShadows and Highlights.

NOTE:The illustration to the Right indicates the various selections inthe Levels Dialogue Box. This exercise starts the correction forTo Apply Auto Levels:

Click Auto Dialogue Box:

The Illustration to the Right indicates the result of Auto Adjustment.

NOTE: The data is distributed differently across the histogram,indicating that adjustments have been made to correct for imbalances.

NOTE: Distribution from Shadow to Highlight has been corrected butthe overall tone is a little cold compared to the original.

Figure.46. Preview Checked

Figure 47...Levels Adjustment Dialogue BoxDe-saturation to improve the purity of the color and also adjusts theContrast.

NOTE: The Levels tool changes color, and contrast together (SeeHistogram Distribution.) Un-check and Check the Preview Button forAuto and Eyedropper to compare and evaluate the Changes.


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Step 4. LEVELS EYE DROPPER ADJUSTMENTThese adjustments are fine tuned to address distribution of Levels inthe Shadow, Highlight and Midpoint.

Note: the Eyedroppers below Options. Right Eyedropper correctsShadow Tones, The Left sets Highlights and the Middle corrects forMidtones.

Eyedropper Corrections:Make a New Adjustment Layer and Select Levels

Choose the Left Eyedropper: Position the eyedropper tool on theimage over darkest spot on the image. Click to select

Select the Right Eyedropper: Position over the brightest area (Whitewindow frames on Cupola) and click

Select the Middle Eyedropper: Position on a neutral Mid-point grayarea, (the sign in the water is within this range) Click.

Figure.48.Levels Eyedropper Adjustment


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Step 5. BRIGHTNESS AND CONTRAST CORRECTIONSThis exercise will address the Flatness, or lack of Contrast in the image.This tool allows you to see a quick change in Brightness and Contrastadjustments affecting the ratio from Complete Dark to Full Light.Brightness and Contrast changes are applied Linearly. ExperiencedPhotoshop users prefer to use the Curves Capability because CurvesAdjustments can be applied over multiple ranges. The Curves tool isvery complex. Instructions for making changes using Curves, can befound in tutorials included inAdobe Classroom in a Book, Peachpit

Press Photoshop Visual Quick Start Guide and the PhotoShop SoftwareManual..

Brightness and Contrast Corrections:Make a New Adjustment Layer and Select B rightness and Contrast

Move the Sliders in the Brightness and Contrast Scale and observethe changes to these ratios.

NOTE:The top Illustration to the Right shows the change when the

Contrast Slider is set at +10. Move the Sliders and Note the changes toyour image when moving the Sliders in each Adjustment Scale.

NOTE:The bottom illustration to the Right shows the Brightness andContrast Adjustment illustrating a Plus 10% change in the Contrastsetting only.

Figure 49.


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Step 6. HUE SATURATION AND LIGHTNESS CORRECTIONSThese adjustments will also correct for the Purity of Color by changingthe

Hue (Colors) of an image for each of the color spaces represented:Red, Yellow, Green, Cyan, Blue, and Magenta. These Hues can beadjusted individually or adjustments can be applied to all selections inthe Master Setting

Saturation adjustments Affect the purity of the color within the image.

Lightness settings change the Value of color as it would berepresented on a scale from Black to White.Step 6 Continued:

Make a New Adjustment Layer and Select Hue/Saturation

Move the Sliders in the Dialogue box and observe the changes.(See Master Edit Dialogue Box. Pull Down this Menu to choose

individual Hues.)

NOTE:The Illustrations of the Master Color Space Setting to Plus 10%

Step 7. COLOR BALANCE CORRECTIONSThis adjustment will address the Magenta Color Cast in the Sky.Color Balance adjustments are made to Color in specific Tonal Areas.In the illustration to the right, in the Color Balance Dialogue Box,

Midtones was selected because this exercise is to correct the sky color,which is a mid-tone in this image.

Make a New Adjustment Layer and Choose Image, Adjust ColorBalance

NOTE: The slider for Magenta was moved toward the Green scale toget rid of the Magenta in the sky. Toggle the Preview on and Off to see

Figure 50. Hue, Saturation, Brightness Adjustments

Figure 51. Color Balance to Adjust for Magenta Color Cast


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the changes to your image.

Figure 52.Comparison between Original Image and All Changes.

Figure 53.Comparison between Original Image and All Changes.


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Step 8. FINE-TUNING CORRECTIONS

The illustration Below shows the Adjustment Layers in the LayersDialogue Box. By opening each Adjustment Layer Dialogue Box FINE-

TUNING adjustments and making comparisons can be easily achievedsimply by opening Adjustment Layer Dialogue Boxes and by Openingand Closing Adjustment Layers in the Layers Menu or Toggling Previewon and off in the Adjustment Dialogue Box.

Figure 54.NOTE: In the Illustration Top Right, two of the Layers (Color Balanceand Hue Saturation) are toggled OFF showing only the Brightness andContrast Adjustments.

NOTE: In the Illustration Bottom Right, the Hue/Saturation DialogueBox has been opened automatically by clicking on this AdjustmentLayer. Clicking the Eye on or Off in the Far Left Column of theAdjustment Layer will toggle that layer on or off.

Figure 55.

Figure 56.


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Step 9. Sharpening

The final step in adjusting an image is to apply globalsharpening if the image is in need of it. With photographicimages, the Unsharp Mask in Photoshop is the preferredtool to accomplish sharpening.

UnSharp Mask, Applied to the Entire RGB Image

Amount controls how weak or strong the mask image thatis blended in will be. This will affect how much edgecontrast will be added and how much apparent sharpnesswill result. If set too low, no changes will be seen, but if settoo high, the inverted halos from the mask will be visible inthe final image and will look artificial.

Amount Settings:Start at an Amount setting of100, with a setting of Radius0.8, and a Threshold setting of 3 for objects.

For faces, portraits and Images with a resolution of 300 ppi,set Amount for 100 with a Radius 1.5 and a Threshold of 6.Experiment with many combinations to learn how not tooverdo it.

Radius controls the degree of unsharpness the maskimage will have. Thus, it determines the width of the halosthe mask will produce. The higher the radius the moreevident the sharpening effect will be. Set too low, the effectwill be invisible or too subtle to be effective. The

appearance of the halo will also vary with the content of the

image since the amount of contrast already present will playa role.

Figure 57.


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Radius Settings:

Radius = 1.0 is a good setting to start with. A range of 0.6 to2.0 are the most useful, depending on the resolution, filessize and amount of fine detail in the image. Choose asmaller Radius setting for fine detail, small file size or lowresolution.

Threshold Settings:Higher threshold values exclude areas of lower contrast.

Human faces or detailed images require values greaterthan 1 or 2, possibly up to 5 or more. For inanimate objects,0 or 1 are the most useful. For other types of subjects try 3or 4. This control has little effect at high values. The effectof Threshold settings on a photographic image is moreapparent between low values of 0 to 5.

Threshold selects how adjacent pixels are considered indetermining what is an edge. Proper settings preventsharpening of unimportant detail, concentrating on detailthat should stand out. Set too low, sharpening will beapplied to every edge or change of tone throughout theimage including such things as film grain. If set too high, notransitions will be viewed as being edges and nosharpening will result.

To Apply an Unsharp Mask to the entire RGB Image:

1. Pull Down the Filters Menu

2. Choose Sharpen>Unsharp Mask

Figure 58.

3. Apply the settings suggested in this tutorial.

4. Check and Uncheck Preview to see the changes compared tothe original image.

Note: Applying the Unsharp Mask to the entire RGBimages causes changes to affect all RGB Channels. This

approach may not provide sufficient control. An alternatemethod is to apply the Unsharp Mask to only the LightnessChannel. The next Tutorial explains how to do this using theLab Mode instead of the RGB Mode.


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Tutorial: Applying an Unsharp Mask to Lab Color

Channels:When using the Unsharp Mask Filter on the RGB image,the same effect happens to all of the edges in yourphotograph and for certain areas of the image, a particularsetting may be too much. Another way to control theamount of sharpening is to only affect the lightness orbrightness of the image not the entire image. This is thebest way to affect the sharpness of the image without

causing odd effects or bringing out too much grain. Inorder to do this you will use channels and will work in adifferent Color Mode called Lab Color.

Lab color mode is best because it divides its the colorinformation of an image, or channels, into Lightness, Plusa, and b channels, which makes it possible to only controlthe Lightness information that applies to the edges of imageareas without effecting color information.

1. The sharpening process should only be appliedafter you have completed all the other modificationsyou need to do...its the last step.

2. You will need a full color image.

Convert the image to Lab color.Pull down the Image Menu and chooseImage mode Lab color

Figure 59.


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3. Selecting the Lightness Channel

Click on the Channels tab in the layers palette.

Click on the channel labeled Lightness. You will alsonotice the image goes to a grayscale. Thats normal.

4. Apply Unsharp MaskGo to Filter Sharpen Unsharp MaskFollow the basic suggestions below:

Amount: 120% to 220% (image varies)Radius: 1.0 to 1.2 pixelsThreshold: 0When you have the results you like click OK.

5. Convert image back to RGBPull Down the Image menu and choose:Image mode RGB

Compare the difference in images sharpened in thesetwo different ways. Compare the images bothonscreen and in a printout. Figure 62.

Figure 62.

Figure 60.

Figure 61.

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