After learning how to use Levels in Photoshop, you should never need to use other tools again. Brightness/Contrast, Variations and Colour Balance commands tend to make changes to a photo which can improve one area at the detriment of another.

Adjustment Layers

When performing changes with levels, make sure you make them with Adjustment Layers (at the bottom of the Layers Palette). Doing it this way ensures that you can go make and make further changes without sacrificing the quality of the image.

Histograms

A Histogram is a graph which maps the tonal properties of an image. You can view it in the Levels dialog (CMD-L). It has its own palette as well.

Highlights are represented at the right end of the scale and shadows on the left.

The Eye Dropper tool is a essential, along with the Info Palette, to measuring the results of your work. If you CMD-Click with the Eye Dropper tool, you will leave a sampler on the image. It can be useful to mark different tones in the image. They remain in the files, even if it is saved and closed.

YOU GOTTA TRY THIS:

"Colour Match" is a really hot new addition to Photoshop. Open an image you wish to improve. Open a second image which has similar, but better colour & contrast.

Go "Image >Adjustments >Match Colour". Change the "Source" pop-up to the image which has the better colour/contrast. If the image has multiple layers or Adjustment Layers, make sure you select "Merged" from the "Layer" pop-up. Watch the magic ensue!

You can even help Photoshop do a better job. Simply go back to the better photo and select the optimal area of the photo. Photoshop will use that area to improve the weaker photo.

GRADIENT MAP:

"Image >Adjustments >Gradient Map" does an interesting thing. It converts a photo to grayscale, then converts the light/dark values to a single colour.

Colour Correction

The Fab Four

The four properties to address in colour correction:

• Tonal range: Adjust the lightest and darkest areas of the photo.
• Colour casts: Adjust mid tones to ensure they are indeed neutral (no colour casts).
• Contrast: Optimize contrast in key areas of the photo.
• Blur: Apply sharpening as needed.

Levels

Moving the White Point or Black Point to the centre increases the contrast. Moving the mid point re-maps the mid tones of the image.

The Output levels are not used in colour correction, but they can be used to compensate for the lack of tonal range in a specific output device.

Ensure that you do not make too drastic changes within the Levels dialog. This can cause banding (posterization).

The Eye Dropper tools within the Levels dialog is used to set the light, mid and black points in the image. Simply select one of the tools and click in the corresponding area of the image.

Sharpen: Unsharp Mask

When sharpening an image, you should ask a few essential questions:

• What is the purpose of the image. Will it be used in print, on the Web? Will it be archived. Will it only be used once, or over and over again in corporate publications?
• At what size will this image be reproduced?
• Should you edit individual channels or the whole image globally?

There are no magic numbers for the Unsharp Mask filter. You have to make a decision on the values to enter.

Unsharp Mask: Amount

The sharpening illusion depends on a light/dark halo effect. The Amount value determines the intensity of the halo, but not its width. High Amount values cause very high contrast halo effects which are more harmful to the image. (80-120)

Unsharp Mask: Radius

The Radius setting controls the width of the halo. The wider the halo, the more obvious the sharpening effect. Radius is your first setting, because it is most dependant on the content of the photo. You should try to keep this value between 0.5 and 1.5. The less detail in your image, the higher the Radius number can be.

Unsharp Mask: Threshold

Threshold acts as a damper to the two other variables in UnSharp Mask. Threshold tells Photoshop how far apart two pixels' tonal values have to be before they are affected by the filter.

The Threshold file is useful for getting a grasp on what the three Threshold variables do to an image. Play with this to try to wrap your brain around it.

Sharpen Together Now

The steps involved in these are a bit un-intuitive, so we'll do them together. We'll use two different methods on these files. One is a simple "Unsharp Mask". The other involves using the "High Pass" filter on a duplicate layer.

Correcting Mid Tones

We'll examine two different methods for changing mid-tones in a photo. The two techniques take the guess work out of fixing these hard to identify areas in a photo.

Auto Options

If you're working in your Levels Adjustment Layer, you can use the Auto button. You need to make sure that the correct settings are applied. You can get to the Auto settings via the Levels palette flyout menu or by simply option-clicking on the Auto button.

Enhance Monochromatic Contrast:

Clips all channels identically. This preserves the overall color relationship while making highlights appear lighter and shadows appear darker. The Auto Contrast command uses this algorithm.

Enhance Per Channel Contrast:

Maximizes the tonal range in each channel to produce a more dramatic correction. Because each channel is adjusted individually, Enhance Per Channel Contrast may remove or introduce color casts. The Auto Tone command uses this algorithm.

Find Dark & Light Colors:

Finds the average lightest and darkest pixels in an image and uses them to maximize contrast while minimizing clipping. The Auto Color command uses this algorithm.

Converting to Greyscale

Converting images to greyscale is more flexible than ever in Photoshop CS5. Now you can use the "Black & White" adjustment layer to fine tune your conversion in a non-destructive manner.

Assignment:

• Set your desktop to grey. Or set Photoshop to "Full Screen with Menu Bar".
• Open one image at a time.
• Take a moment to look at the image.
• Take note of what you think is wrong with it.
• Don't make unnecessary changes.
• Name your layers something meaningful!
• ALWAYS work on layer copies, adjustment layers and use Smart Filters.

How to Get an "A"

To earn an "A", you will

• Not damage the photo. Opt for more subtle improvements, rather than drastic ones.
• Use the demonstrated process
• Name all of your layers
• Make the right corrections to the right photo. They do not all require all of the different types of corrections.

You will hand in a folder with your PSD files named "lastname firstname 010". Drop them in my Drop Box.