Enhancing Images with Autolevels and Levels

When you take an image with your digital camera, it is possible to change the appearance of the image in many ways.

One of these is by adjusting the levels through the Enhance menu option and using the Autolevels and the Levels features.

Download the two images displayed below. Click on the thumbnail images to display the larger images and download the images to your hard drive.

To download the larger image, place your mouse pointer on the larger image, RMC (Right Mosue Click), and select Save Image As

Click this thumbmail to view the larger Houses of parliament image		Click this thumbnail to view the larger French Alps image

Using the Autolevels feature
The Auto Levels command defines the lightest and darkest pixels in an image, and then redistributes intermediate pixel values proportionately. Because Auto Levels adjusts each color channel (red, green, and blue) individually, it may remove or introduce color casts.

Auto Levels gives good results when an image with an average distribution of pixel values needs a simple contrast adjustment.
(Adobe Photoshop Help Index)

Start Adobe Photoshop Elelments - open the large Houses of Parliament image.

Select Enhance > Autolevels

You should notice a slight change in the tone of the image.

Click on the Undo button on the toolbar and then the Redo button to compare the effect of the Enhance > Autolevels feature. You may feel you don't want to allow Photoshop Elements to control the colours on your image, and so you can do it manually.

Using the Levels feature
The Levels dialog box lets you correct the tonal range and color balance of an image by adjusting intensity levels of the image's shadows, midtones, and highlights. The Levels histogram serves as a visual guide for adjusting the image's key tones.
(Adobe Photoshop Help Index)

Open the larger image of the French Alps

Select Enhance > Autolevels

I find the contrast is too strong and do not like the result. Click Undo to restore the image to the previous colour values.

Select Enhance > Brightness/Contrast > Levels and a dialogue box similar to the one on the left below appears.

Start Image		End Image
Notice the triangles are on the outside of the histogram		Notice the left and right triangles have been moved to extremeties of the histogram

The histogram shows the black and white levels. You will notice there is a gap on each end of the range.

Use your mouse to move the small triangle on the left of the base line to the right so it is under the left side of the histogram.

Move the triangle on the right side of the baseline to the left so it is under the right side of the histogram.

See the Start and End images above to see how the histograms will appear.

You should see a change in the image similar to the images below. Notice the sharper contrast and more detail.