2a Contrast

Increasing Contrast

Note: if you are not able to start the Paint Shop Pro program at school because the link to the program is missing then try downloading and opening this image in pspimage format.

What do you think of the photograph below (Le Fort Carré in Antibes, France)? It is an old photograph, and rather faded - the contrast is too low and needs increasing. This is a straightforward adjustment to make, but first you will need to copy the photo onto your hard disk and then open it in Paint Shop Pro, as explained on the Basics page.

There are several ways to improve the contrast, some of which cause Paint Shop Pro to make an automatic adjustment. In general, the automated adjustments WILL improve your pictures, but if you are a professional or a perfectionist then you will usually choose to make a manual adjustment because the automatic adjustment is never perfect and sometimes even does a poor job, so you may want take the time to make the adjustment yourself. Also, the automatic adjustments are 'too quick and easy' to be worth spending a lot of time on this course, so we will focus on manual adjustments.

To adjust the contrast automatically do one of the methods below. Try these just to see the effect but then undo each change with Ctrl+Z so that you can make a manual adjustment afterwards.

	Choose Adjust > One Step Photo Fix. When you make this selection Paint Shop Pro tries to optimize not only the contrast but also the colour balance too.
	Choose Enhance Photo > One Step Photo Fix (the same effect as above, of course)
	Choose Enhance Photo > Automatic Contrast Enhancement.

To adjust the contrast manually:

Choose Adjust > Brightness and Contrast > Brightness/Contrast (or Shift+B). A dialogue box will open. This is our first meeting with a Paint Shop Pro dialogue, so there are a number of important points to note:

Most dialogues that correct images, apply effects, or modify selections offer two preview windows that show the image before and after changes are applied. You can use the window controls to zoom the preview in or out, pan it or proof (preview) changes on the actual image.

You can show or hide the preview windows. My recommendation is that you always hide them by clicking the Show/Hide Previews button and then use the main image window to proof changes. I recommend that you turn on 'automatic proofing' by clicking the Autoproof button . so that Paint Shop Pro automatically applies all dialogue settings to the main image window each time you change a setting.

If you use the Proof button without of the Autoproof button then you will need to click the Proof button every time you make an adjustment in order to see the adjustment applied to the main window.

To make an adjustment such as a contrast adjustment you can use the adjustment control in various ways:

	Type a new number between 0 and 100.
	Click the up or down buttons to increase or decrease the value in steps of one.
	Pull down a slider that you can slide left or right to the desired value
	Use the displayed slider without pulling down the larger one - this is the technique I recommend.

Make sure that the Autoproof option is turned on, then adjust the contrast using the slider until the image is as good as possible (check what happens if you use much too much contrast). Note that photographic images should normally contain a tiny bit of black and a tiny bit of white so that you are using all of the available brightness range or 'tonal range'. Be careful not to bleach the clouds so that you see large areas of pure white with no detail. DON'T save your work just yet.

There are other ways to change the contrast manually including:

	Adjust > Brightness and Contrast > Curves
	Adjust > Brightness and Contrast > Histogram Adjustment
	Adjust > Brightness and Contrast > Levels

but these controls are more sophisticated than we need for a simple contrast adjustment so we won't 'use a sledgehammer to crack a nut'.

Important: Do NOT be tempted to use the Brightness/Contrast panel to adjust the brightness for there is a much better, more sophisticated way.

The contrast control offers a good and easy way of increasing the contrast in a picture, but I advise you not to use it to treat pictures that are suffering from too much contrast. This is because the use of the contrast control in that situation would leave you with a picture that contains no pure black or pure white, and most pictures should contain a little of each. Correctly solving the problem of excessive contrast is a topic that I will return to at the end of this lesson.

I suggested above that photographic images should normally contain a tiny bit of black and a tiny bit of white - it's a bit difficult to know when you have got just the right amount of contrast so that the above condition (a little bit of black and a little bit of white) is satisfied, so let's get some help from the computer. Do Ctrl-Z to return to the original image - do it several times if necessary or you could even choose File>Revert to make sure you have returned to the version of the image that is on the disk (I'm assuming you haven't saved your changes yet).

Choose Adjust > Brightness and Contrast > Histogram Adjustment.

This is the third way to manually lighten the dark parts of the picture. You will see a histogram looking line the one at right. Also, we see a red shape which indicates how much of the picture is bright or dark according to how high the 'mountains' are. In our graph, we have a tall 'mountain' near the centre but we notice that the mountainous landscape does not extend all the way to the sides - this means that our picture does not contain any pure black or pure white as it usually should.

We can fix this problem by moving the two outermost triangles under the graph - try moving each one until is just under the edge of the GRAY landscape, as shown at right. The red landscape shows what the landscape will be like after we make this change. If autoproof is turned on then you should see that your picture uses the full tonal range from black to white and looks much more lively than it used to.

You're probably wondering what happens if you move the middle triangle so try that too - you will see that it is a way of making the whole picture brighter or darker - it's actually a better way of changing the brightness than using the 'official' brightness control, which usually does not give the desired result. Note how the line curves up when the image is lighter and down when we darken it - we will see that again in the next lesson when we meet the curves control.

Save your work in your folder before moving on.

Decreasing Contrast

What about the picture of a small Japanese fountain, shown below?

Although the overall brightness is OK, the high contrast makes the picture rather harsh and makes it difficult to see detail in the leaves to the left of the fountain. For pictures like this that have too much contrast the contrast control does not work well but the histogram adjustment control has a feature that makes it a good option.

Open the picture in Paint Shop Pro and choose Adjust > Brightness and Contrast > Histogram Adjustment. To reduce contrast without losing whites or blacks, use the midtones adjustment at the right of the dialog. Slide the slider up just a little until the image has lost its harshness, but make sure you don't go too far or the picture will no longer look natural.

On the histogram, the line has been lifted on the left, meaning the darker parts (but not the black parts) have been lightened slightly. The line has been pulled down on the right, meaning that the lighter parts (but not the white parts) have been darkened. The central part of the curve is less steep than before, and it is this that corresponds to reduced contrast. The pure black and pure white in the picture are unchanged since the ends of the line did not move. Save your work.