Dithering in Photoshop

Dithering in Photoshop:

What is Dithering?

The process of dithering places pixels of two different colors next to each other to suggest the appearance of a third color. For example, in a grayscale photograph, a black pixel is placed next to a white pixel to suggest a shade of gray when viewed from a distance. This same process is used with color pixels to increase the number of colors that can be represented by a limited palette.

Unless you’re using the Exact color table option, the color table may not contain all the colors used I the image. To simulate colors not in the color table, you can dither the colors. Dithering mixes the pixels of the available colors to simulate the missing colors.

Choose a dither option from the menu, and enter a value for the dither amount. A higher amount dithers more colors, but may increase file size. You can choose from the following dither options:

None:

Does not dither colors but instead uses the color closest to the missing color. This tends to result in sharp transitions between shades of color in the image, creating a posterized effect.

Diffusion:

Uses an error – diffusion method that produces a less structured dither than the Pattern option. To protect colors in the image that contain entries in the color table from being dithered, select Preserve Exact Colors. This is useful for preserving fine lines and text for Web images.

Patterns:

Uses a halftone – like square pattern to simulate any colors not in the color table.

Noise:

Helps to reduce seam patterns along the edges of image slices. Choose this option if you plan to slice the image for placement in an HTML table.

Filters - Choosing effect

Filters - Choosing effect

The built-in filters are grouped into 14 submenus. In addition, any third-party filters installed appear at the bottom of the Filter menu.

Artistic filters

Achieve a painterly or special effect for a fine arts or commercial project. For example, use the Cutout filter for collages or type treatment. These filters replicate natural or traditional media effects.

Blur filters

Soften a selection or an image. Blur filters are useful for retouching. They smooth transitions by averaging the pixels next to the hard edges of defined lines and shaded areas in an image.

Note: To apply a Blur filter to the edges of a layer, be sure to deselect the Preserve Transparency option in the Layers palette.

Brush Stroke filters

Like the Artistic filters, the Brush Stroke filters give a painterly or fine-arts look using different brush and ink stroke effects. Some of the filters add grain, paint, noise, edge detail, or texture to an image for a pointillist effect.

Distort filters

Geometrically distort an image, creating 3D or other reshaping effects. Note that these filters can be very memory intensive.

Noise filters

Add or remove noise, or pixels with randomly distributed color levels. This helps to blend a selection into the surrounding pixels. Noise filters can create unusual textures or remove problem areas, such as dust and scratches, from an image. The Add Noise filter can be used to reduce banding in feathered selections or graduated fills or to give a more realistic look to heavily retouched areas.

Pixelate filters

Sharply define a selection by clumping pixels of similar color values in cells.

Render filters

Create 3D shapes, cloud patterns, refraction patterns, and simulated light reflections in an image. You can also manipulate objects in 3D space, create 3D objects (cubes, spheres, and cylinders), and create texture fills from grayscale files to produce 3D-like effects for lighting.

When using the Clouds filter, generate a more stark cloud pattern by holding down Alt (Windows) or Option (Mac OS) as you choose Filter> Render > Clouds.

Sharpen filters

Focus blurry images by increasing the contrast of adjacent pixels. They include the Sharpen Edges (Photoshop) and Unsharp Mask filters, which find and sharpen areas where significant color changes occur (such as the edges). The Unsharp Mask filter is commonly used for high-end color correction.

Sketch filters

Add texture to images, often for a 3D effect. The filters also are useful for creating a fine-arts or hand-drawn look. Many of the Sketch filters use the foreground and background color as they redraw the image.

For a truer effect, change the foreground color to one of the common Conté Crayon colors (black, sepia, sanguine) before applying the filter.

Stylize filters

Produce a painted or impressionistic effect on a selection by displacing pixels and by finding and heightening contrast in an image. After using filters such as Find Edges and Trace Contour (Photoshop) that highlight edges, you can apply the Invert command to outline the edges of a color image with colored lines or to outline the edges of a grayscale image with white lines.

Texture filters

Give images the appearance of depth or substance, or add an organic look.

Video filters

Include the NTSC (National Television Standards Committee) Color filter, which restricts the gamut of colors to those acceptable for television reproduction, and the De-Interlace filter, which smooths moving images captured on video.

Other filters

Let you create your own filters, use filters to modify masks, offset a selection within an image, and make quick color adjustments.

Digimarc filters

Embed a digital watermark into an image to store copyright information.

   

getting started with photoshop - Editing Layer using Layer Effects & Styles

Editing Layer using Layer Effects & Styles

 Editing styles

You edit a layer's style by adjusting its effect settings. In Photoshop, effect settings appear in the Layer Style dialog box. In ImageReady, effect settings appear in the context-sensitive Layer Options/Style palette--the name of the palette changes depending on the effect you select.

Note: ImageReady provides a subset of the effect settings provided by Photoshop.

Photoshop Layer Style dialog box. Click a check box to apply the default settings without displaying the effect's options.

Click an effect name to display the effect's options. 

To edit a layer style:

1. Do one of the following:

• In the Layers palette, double-click an effect displayed below the layer name. (Click the inverted triangle next to the "f" icon to display the effects contained in the style.)
• (Photoshop) Double-click a layer thumbnail, and select the effect you want to edit on the left side of the dialog box.

2. Set one or more of the following options in the Layer Style dialog box (Photoshop) or the context-sensitive Layer Options/Style palette (ImageReady). The available options depend on the selected effect:

In Photoshop, you can edit multiple effects without closing the Layer Style dialog box. Select an effect on the left side of the dialog box to display an effect's options.

Angle

Determines the lighting angle at which the effect is applied to the layer. In Photoshop, you can drag in the document window to adjust the angle of a Drop Shadow, Inner Shadow, or Satin effect.

Anti-alias

Blends the edge pixels of a contour or gloss contour. Most useful on shadows with a small size and complicated contour.

Blend Mode

Determines how the layer style blends with the underlying layers, which may or may not include the active layer. For example, an inner shadow blends with the active layer because the effect is drawn on top of that layer, but a drop shadow blends only with the layers beneath the active layer. In most cases, the default mode for each effect produces the best results. 

Choke

Shrinks the boundaries of the matte of an Inner Shadow or Inner Glow prior to blurring.

Color

Specifies the color of a shadow, glow, or highlight. You can click the color box and choose a color. 

Contour

With solid color glows, contour allows you to create rings of transparency. With gradient filled glows, contour allows you to create variations in the repetition of the gradient color and opacity. With bevel and emboss, contour allows you to sculpt the ridges, valleys, and bumps that are shaded in the embossing process. With shadows, allows you to specify the fade. 

Distance

Specifies the offset distance for a shadow or satin effect. In Photoshop, you can drag in the document window to adjust the offset distance.

Depth

Specifies the depth of a bevel and is a ratio of size. It also specifies the depth of a pattern.

Global Angle

Turns on global lighting for the effect. Global lighting applies the same angle to all effects with the Global Angle option selected, giving the appearance of a consistent light source shining on the image. Deselect Global Angle to assign a local angle to Drop Shadow, Inner Shadow, and Bevel effects. 

Gloss Contour

Creates a glossy, metal-like appearance and is applied after shading a bevel or emboss.

Gradient

Specifies the gradient of a layer effect. In Photoshop, click the gradient to display the Gradient Editor or click the inverted arrow and choose a gradient from the pop-up palette. In Photoshop, you can edit a gradient or create a new gradient using the Gradient Editor. In ImageReady, click the inverted arrow next to the gradient sample and select a gradient from the list, or choose a gradient type from the pop-up list. You can edit the color or opacity in the Gradient Overlay panel the same way you do in the Gradient Editor. For some effects, you can specify additional gradient options. Reverse flips the orientation of the gradient, Align With Layer uses the bounding box of the layer to calculate the gradient fill. Scale scales the application of the gradient. You can also use the mouse to move the center of the gradient by clicking and dragging in the image window. Style specifies the shape of the gradient.

Highlight or Shadow Mode

Specifies the blending mode of a bevel or emboss highlight or shadow. 

Jitter

Varies the application of a gradient's color and opacity.

Layer Knocks Out Drop Shadow

Controls the drop shadow's visibility in a semitransparent layer.

Noise

Specifies the amount of random elements in the opacity of a glow or shadow as you enter a value or drag the slider.

Opacity

Sets the opacity of the layer effect as you enter a value or drag the slider.

Pattern

Specifies the pattern of a layer effect. In ImageReady, click the inverted arrow next to the pattern sample and choose a pattern from the list. In Photoshop, click the pop-up palette and choose a pattern. Click the New preset button  to create a new preset pattern based on the current settings. Click Snap to Origin to position the origin of the pattern with that of the document if Link With Layer is selected, or to position the origin with the top left corner of the layer if it is deselected. Select Link With Layer to specify that the pattern moves with the layer as it is relocated, and drag the Scale slider or enter a value to specify the size of the pattern. You can drag a pattern in the layer to position it while in this panel. The position can be reset with the Snap to Origin button. There must be at least one pattern loaded for the pattern option to be available. You can also load patterns using the Preset Manager.

Position

Specifies the position of a stroke effect as Outside, Inside, or Center.

Range

Controls which portion or range of the glow is targeted for the contour.

Size

Specifies the amount of blur or the size of the shadow. 

Soften

Blurs the results of shading before compositing to reduce unwanted artifacts.

Source

Specifies the glow source for an inner glow. Choose Center to apply a glow that emanates from the center of the layer's content, or Edge to apply a glow that emanates from the inside edges of the layer's content.

Spread

Expands the boundaries of the matte prior to blurring. 

Style

Specifies the style of a bevel: Inner Bevel to create a bevel on the inside edges of the layer contents, Outer Bevel to create a bevel on the outside edges of the layer contents, Emboss to create the effect of embossing the layer contents against the underlying layers, Pillow Emboss to create the effect of stamping the edges of the layer contents into the underlying layers, or Stroke Emboss to confine the emboss to the boundaries of a stroke effect applied to the layer. (Note that the Stroke Emboss effect will not be visible if no stroke is applied to the layer.)

Technique

For bevel and emboss, Smooth blurs the edges of a matte slightly and is useful for all types of mattes, whether their edges are soft or hard. It does not preserve detailed features at larger sizes. Chisel Hard uses a distance measurement technique and is primarily useful on hard-edged mattes from anti-aliased shapes such as type. It preserves detailed features better than the Smooth technique. Chisel Soft uses a modified distance measurement technique and, while not as accurate as Chisel Hard, it is more useful on a larger range of mattes. It preserves features better than the Smooth technique. For glows, Softer applies a blur and is useful on all types of mattes, whether their edges are soft or hard. At larger sizes, it does not preserve detailed features. Precise uses a distance measurement technique to create a glow and is primarily useful on hard-edged mattes from anti-aliased shapes such as type. It preserves features better than the Softer technique.

Texture

Allows you to specify a pattern used to texture the bevel effect. Scale allows you to scale the size of the texture. Link With Layer specifies that the texture moves with the layer as it is relocated. Invert inverts the texture. Depth varies the degree and direction (up/down) to which the texturing is applied. Snap to Origin controls the snap of the pattern's origin with that of the document if Link With Layer is disabled and with the top left corner of the layer if it is selected. You can also drag the texture with the mouse to position it while in this panel.