This is a pretty awesome tutorial on everything you need to know about Photoshop. From the basics to the explination of almost everything in Photoshop.
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Tools Palette: Self explanatory - the palette that contains the tools that can be used to directly edit the image.
Tool Options: A selection of options that relate to the currently selected tool and alter its effects.
Drop down menus: Standard drop down menus as seen in most Windows and Macintosh applications. Offers access to most of Photoshop's features. Commands for the drop down menus in these tutorials are written in bold.
Info Palette: Shows information about the current image, or shows a thumbnail via which you can navigate the image. Information provided includes crop/selection area, file size, image dimensions, etc.
Colours/Styles Palette: Allows you to select a colour via RGB sliders or preset web-safe colours ('Swatches'). Also lets you apply layer styles - preset combinations of layer styles (effects) that can achieve effective results if you're in a hurry. Use the expansion arrow (just undereath the close button) to load more styles that are included with Photoshop.
History Palette: Gives a list of actions that can be undone - lists around one hundred. You can save snapshots to return to at key points in your image creation, or return to the saved file/a recent step. Also contains actions and tool presets for the currently selected tool.
Layers Palette: The layers palette has many features, too many to list here. They are described later in the tutorial.
Layer Opacity: The opacity of the current layer, 0-100%.
Blending Mode: The manner in which this layer interacts with layers below it. See below.
Active/Linked Layers: A small paint brush icon appears in this space to indicate the active layer, and chain icons signify other layers that are linked with the active layer.
Layer visibility: An eye in this area signifies that the layer is visible, and an empty box means it is hidden from view and exempt from formatting.
Layers: Two example layers showing an example background layer and new (transparent) layer (Layer 1).
New Fill/Adjustment Layer: Creates a layer that can add a gradient to or adjust the hue, etc. of the layer below.
New Layer: Creates a new layer [ctrl/cmd + shift + N].
Delete Layer: Deletes the currently selected layer.
New Layer Set: Creates a folder for layers to be put into for easy organisation of layers.
New Layer Mask: Creates a sub-layer with which you can use all normal tools. Adding black to a layer mask, for example, means that that part of the layer is invisible.
Layer Effects (Styles): Applies various effects to the current layer - can also be reached via Layer || Layer Style.
Normal/Dissolve: All layers appear as normal - dissolve doesn't blend the colours that are layered, but instead applies the colour to pixels at random in accordance.
Darken > Linear Burn: Subtly different methods of darkening the layers beneath the selected layer.
Lighten > Linear Dodge: Subtly different methods of lightening the layers beneath the selected layer.
Overlay: Crudely put, reduces the opacity of the layer.
Soft Light > Pin Light: Methods of lightening layers below the current one at varying strengths.
Difference/Exclusion: Quite complicated - this is as it appears in the PS help files: "Looks at the color information in each channel and subtracts either the blend color from the base color or the base color from the blend color, depending on which has the greater brightness value. Blending with white inverts the base color values; blending with black produces no change." Exclusion is pretty much the same but at lower contrast.
Hue > Luminosity: Effects the respective value of the layer below.
Marquee Tool: The marquee tool selects areas within a layer. It is capable of selecting an elliptical, square, single column, and single rows.
Move Tool: The move tool can move around all objects within a layer. To move entire image, Flatten the layers by selecting Layer > Flatten Image.
Lasso Tool: The lasso tool can select areas within in a layer that can’t be reached with the marquee tool.
Magic Wand: The magic wand is an automatic selection tool. It selects everything in the layer.
Cropping Tool: This tool changes the size of the image. To use, Select the area you want to crop and then press enter.
Slice Tool: Makes Guidelines.
Heal Brush Tool and Patch Tool: The patch tool is another form of the heal brush. It is in the options for the heal brush. The Heal Brush deletes the high contrast of a picture and is used when retouching a photo. To use, hold down alt while clicking on the source (an area that looks like what you want the damaged part to look like) and drag the mouse around the damaged picture to repair it.
The patch tool fixes damaged parts of a picture by blending the damaged part with a better one. Just use the patch tool to select part of the image, then drag the selection to another part of the image. This will combine the selections.
Pencil Tool and Brush Tool: Draws or paints a line. Same as the pencil or brush tool in paint. Change the color of the paint brush by clicking on the color picker.
Clone Stamp Tool and Pattern Stamp Tool: The clone stamp tool duplicates part of the image. Hold down alt while clicking to choose the part of the image which you want to duplicate. Drag the mouse over the damaged area.
The pattern stamp tool can create and save a pattern you want to use over and over again. To make a pattern, use the marquee tool or the lasso tool to select part of the image. Go to Filter > Pattern Maker and click generate. Click on the floppy disk underneath the Tile History called Save Preset Pattern. This will save the pattern. Do not push OK unless you want to fill the entire image with that pattern. Press cancel and select your pattern from Pattern on the top center of Photoshop. Drag the mouse over the area with the pattern stamp tool to edit the picture.
History Brush Tool and Art History Brush: The history Brush tool can go back and undo certain changes in a picture. To delete everything you did since the opening of the picture simply drag the history brush over the area to be repaired. The history brush works best when transforming snap shots. Using the snap shot will only change certain parts of the picture and can go back in editing to change major errors. To make a Snap Shot, save the picture then click on the small camera on the bottom of the history window. The snap shot will be saved once it is named. If you click on a previous snap shot, you can edit a previous version of your picture. Click on the last snap shot then use the history brush tool to undo the editing to make the unedited section look like the previous snap shot.
The Art history Brush tool can artistically undo an image and warp the original picture. Click on the top snap shot and chose what kind of brush to use on the top of the window under Style. Click on the area you want to edit with the art history brush.
Eraser Tool: This can erase part of the photo in a certain layer. To erase everything in a certain area to make it white, flatten the image or go through every layer to delete that part.
Paint Bucket: Makes an area one color. To edit all layers at one time, click on All layers at the top of the window.
The Blur tool, Sharpen Tool, and Smudge Tool: To use, drag over part of photo you want to edit. The hardest part of this tool is selecting the right strength, brush size and mode. This tool is capable of blurring part of the image, undoing the blur with the sharpen tool, and slightly liquefying with the smudge tool.
The Dodge Tool, Burn tool, and Sponge Tool: To use any of these tools, just drag it over the image. The dodge tool can lighten an image, the burn tool darkens it, and the sponge tool soaks color out of the image.
Text Tool: Puts text in a picture. Click on the picture with the type tool and select a box the size of the area you want to add text. Type in the box then adjust the size of the text box.
Pen Tool: The pen tool can make lines and be used with shape tools to create different shapes. To create lines, use the pen tool to create anchors (the little boxes on a line) and change the shape of the line by moving around the anchors.
Custom Shape Tools: Creates shapes in the image. The custom shapes tools can create all shapes in the shape section located at the top center of the Photoshop window.
Annotation Tool: This can create notes and sound effects in an image. The only difference between the note tool and the text tool is that the note comes up in a little white box and when the note is too long for the given space, there will be a scroll bar. This is usually used in PDF formats and Acrobat Documents.
The audio Annotation tool can add audio notation to the picture. To use, click on the audio notation tool and press start. Record your voice with the microphone then press stop. You can import the audio by File > Import > Annotations. Make sure the file you import is a PDF file or a FDF file.
Eyedropper Tool: Samples a color from the picture, color swatches, or the color picker. To use, click on the color on the image you want to take and right click.
Hand Tool: Moves around image within an object. Is used with the zoom tool when you want to adjust the section of picture you want to look at.
Zoom Tool: Zooms in on part of the picture for closer editing.