• Mar

    The Improved Tone Curve in Corel PHOTO-PAINT X4


    The Tone Curve gives you the ability to make color and tonal corrections by the composite channel (RGB red, green and blue channels combined) or individually. Using a graph, pixel values are plotted along its length. The graph is where you adjust the shadows, midtones and highlights. To access this filter, click on Adjust: Tone Curve.


    The Controls in Depth

    At the top left of the Tone Curve dialog box are two icons. Click on the first one and two panes apear above the Tone Curve, governing before and after states of the image you want to correct. If you click on the button to the right of the first one, you get a single horizontal preview. 

    The Tone Curve is where pixel values are plotted along a curve. This represents a balance between shadows, midtones and highlights. Looking at the graph, the shadows are the bottom of the graph, midtones represent the middle of the graph and highlights are the bottom of the graph.

    To fix problem areas in an image, you add nodes to the tone curve, then drag the curve. If you want to make global changes to the image, use RGB as the active channel and enable the Display all channels checkbox. This brings up a blue line which gives you a reference point when adjusting your images.


    If there are specific areas that you want to address, you can make use of the Eyedropper tool and select those areas in the image window. This will create nodes on the tone curve that you can then adjust to your liking. The histogram at the bottom of the dialog box gives you information about the tonal range and what happens as you make changes.


    Do not drag the eyedropper across the image as it creates too many edit points along the curve. To fine-tune your adjustments, you can choose a style from the style list popup. Your choices are: Curve, Straight, Freehand and Gamma. Another option is to load a preset. To do so, click on the open folder icon to the right of the Presets parameters box. You can also save custom presets to use on other images.

    Clicking on the Auto Balance Tone button equalizes the tonal range of the image with a preset curve.

    The Settings button brings up the Auto adjust Range dialog box. This controls the white and black limit of the image and where you set the outlying (clipped pixels) of the tonal range.

    Directly below this is the Parameters area. Click on the Open Folder icon to access any one of ten predefined curves. The listing appears in the Parameters list box. These serve as a starting point when adjusting your images. Your options are: brighten, darken, default, inverse, lighten, neggamma, posgamma, shadow, solar1 and solarize. When you’ve finished making your adjustments you can save the settings for future use.

    The next area is the Active Channel. You can choose to work on all channels at once or each individual channel.

    Next is the Curve options area. In the popup you have four choices: Curve, Straight, Freehand and Gamma. Of these, the Smooth button below only becomes active when using the Freehand setting.

    The two icons to the lower left in this area allow you to change the position of your curve horizontally, mirroring it back on itself. Note that the X, Y and eyedropper options are grayed out when using this setting. The same thing happens with the Gamma setting. The Gamma setting lets you expose detail in a low-contrast image without any major changes to shadows or highlights. This filter affects all image values, but because it’s curved, the adjustments favor the midtones.

    If you don’t like the way the changes are being applied to your image, click on the Reset Active Channelbutton.

    © Nathan Segal Questions? Write to me.

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