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Tips and Tricks
Selective noise reduction
  1. Duplicate the layer you wish to apply the filter to.
  2. On the higher layer, with a soft-edged brush, erase those areas to which you would like to apply the filter. (It is a good idea to turn off the
    visibility of the background while doing this.)
  3. Apply the noise reduction filter to the lower layer. The effect will only be visible through those areas you erased from the layer above
Painting Shadows
 When you need to make quick painted shadows with any of the brushes, select Behind in the Paintbrush Options palette. This mode allows you to paint only on the transparent parts of a layer. Select the color and opacity and then paint behind any silhouetted object.
Banding in gradient fills
 Don't let banding in gradient fills ruin an otherwise excellent drawing. To minimize this, add a small noise filter. Select Filter/Noise/Add Noise. Enter a small number in the amount box. The banding should be reduced or eliminated, greatly improving the appearance of the fill.
Fix Cropping
 You can crop an image to the height, width and resolution of another image. Select the image with the desired dimensions and resolution. Then select Fixed Target Size and click Front Image in the Cropping Tool Options palette.
Hiding Layers
 You can hide all but one layer by holding the Alt key while clicking on the eye symbol next to the layer you wish to view. Alt+click the symbol again to redisplay all layers.
RAM
The more RAM, the better. When you start editing the image, the computer needs at least twice the size of the file in RAM to edit it. If you have the "undo" function turned on, it may need up to five times the size of the file. When the computer runs out of RAM for editing, the edit time will increase by at least 10 times. One minute will now be 10, because the computer is using your hard disk as a memory.
Undo's
If you make a color correction to a 32 MB file, the computer will need 64 MB for the image, so you can back up one step.
There is a trick to keeping the memory usage down: use the rectangular select tool and select a very small area and copy it to the clipboard. This will dump undo memory, and substitute it with an undo of less than 1 MB. You can now perform the next edit, and not worry about the computer going to the hard disk for memory.
How do I sharpen the image so I don’t have the jagged edges?
Feather selection 2 pixels before copying.
Select > Feather and choose 2
How do I make the background transparent?
After you paste selection into a new transparent file, change mode to Indexed Color.
Image > Mode > Indexed Color and choose Adaptive
Then save as GIF, as only gif can be transparent.
Resizing with Photoshop

When you want to resize an image in Photoshop, you have three methods available:

  • nearest neighbor (resampling)
  • bilinear (interpolations - 4 neighboring pixels)
  • bicubic (interpolations - 16 neighboring pixels - good to enlarge an image)

The first one is just a resampling of the image, while the other two are interpolations.

Resampling an image consists roughly in making its pixels bigger or smaller than they originally are.

Interpolating is a fundamentally different process, in the sense that the color value of the interpolated pixel is computed based on several pixels (surrounding the "unknown" one) of the original image.

  • If you have chosen bilinear, it will use 4 neighboring pixels, if you have chosen bicubic, it will use 16 of them.
  • It is easy to understand that using 16 pixels will give a smoother transition than 4. 
  • What is less easy to see is that you introduce more arbitrary information into the image by doing "bicubic" interpolation than "bilinear". This is good to enlarge an image, as we do not have the missing information.
  • but this is definitely not necessary to reduce an image. We already have all the information in the original image. If you add "smoothing information" when you reduce the image, it will just be blurred, and this is easy to see in Photoshop.
As a conclusion, always use:
  • bicubic interpolation to enlarge an image
  • bilinear (+slight unsharp masking) to reduce its size

Genuine Fractals
To restore part of an image to a previous state you can:
  • Mark the previous state you want to restore and use the History Brush
  • Mark the previous state you want to restore to and use Eraser Tool with the Erase to History option checked in the Option Bar
  • Mark the previous state you want to restore to and make a selection. Choose Edit > Fill and choose History for use

The History Eraser tool is also reached by pressing Alt when using the regular Eraser.
If you double the resolution the file size will approximately be four times the original size.  This is because the pixels are doubled both horizontally and vertically.
Color channels store the color information for an image, and alpha channels store selections or masks you can use when you want to edit specific parts of an image.
The only way to use so called Spot colors is to add a Spot channel. This is the third channel type; the other are the Color channels and the Alpha channels.  Spot colors are colors impossible or difficult to produce with a mix of the traditional CMYK inks (called process colors). Spot Colors are only used in professional printing, not on desktop printers or on the web. Files containing Spot Colors should be saved in the Photoshop DCS 2.0 file format.
Adjustment layers and fill layers have the same opacity and blending mode options as image layers. By default, adjustment layers and fill layers have layer masks, as indicated by the mask icon to the left of the layer thumbnail. If a path is active when you create the adjustment or fill layer, a vector mask is created instead of a layer mask.

To confine the effects of an adjustment layer to a group of layers, create a clipping mask consisting of these layers.
To zoom in on an image without loosing the tool you're currently working with you can press Ctrl + spacebar and click.
To place vector drawing file into Photoshop you will have to convert the file to one of the following format:
  • EPS (Encapsulated PostScript)
  • AI (Adobe Illustrator)
  • PDF (Portable Document Format)
  • PDP (Print Shop Deluxe)
Feathering looses detail, Anti-Aliasing preserves detail.
The Select > Similar command looks at the colors in the selection and finds colors within the same range throughout the image. The Similar command relies on the Tolerance setting in the Magic Wand tool. This also applies to the Grow command.
When you open up a JPG (short for Joint Photographers Expert Group) the image is an a background layer. Before you can change the opacity of this layer, the layer must be converted to a regular layer. The easiest way to do this is to Double click on the layer and just press Enter to have it named Layer 0. The background layer is no longer background and can be treated as a normal layer.
Another way to doing this would be to go Layer > New > Layer from Background.
If you want to make improvements to a layer mask by painting directly into it with black and white:
  • click the Layer mask in the Channel Palette or
  • Alt + click the layer mask
To create a copy of the layer:
  • Press the layer option button and choose Duplicate Layer
  • Drag the layer to the Create A New Layer button in the Layer Palette
  • Right click the layer in the Layers Palette and choose Duplicate Layer
The channels in Photoshop can be looked on as masks. This means that a lot of white in a channel indicates that it is less masked, i.e. more of that channels color will shine through.  Seeing a large amount of white at the red channel indicates a lot of red.

For instance you will see a lot of white in the red channel of a person's eye in a 'red eye' photo. Decreasing this to a more neutral gray will bring out the real color of the eye, and removing the 'red eye'.
Kerning is the process of adding or subtracting space between specific letter pairs. You can control kerning manually, or you can use automatic kerning to turn on the kerning built into the font by the font designer. Tracking is the process of creating an equal amount of spacing across a range of letters.
To make sure the color is within the CMYK gamut - add a spot color.
A spot color is a color that either cannot by reproduced by CMYK or used when printing with colors fewer than four. To make any color with CMYK you have to have 4 passes in the printing press.  With a Spot Color you only need one.

By painting with grayscale tones in a spot channel you can add Spot color to an image.
To compress certain areas of a JPEG image more than others to decrease file size:
  • Use Alpha channel as a mask to compress areas of an image less than other
  • Slice the image
The Single-line Composer attempts to fit all words on a line by adjusting word spacing, if this doesn't work it hyphenates and breaks the line after the hyphen.
Using fractional character widths

By default, type is displayed using fractional character widths. This means that the spacing between characters varies, with fractions of whole pixels between some characters. In most situations, fractional character widths provide the best spacing for type appearance and readability. However, for type in small sizes (less than 20 points) displayed online, fractional character widths can cause type to run together or have too much extra space, making it difficult to read.

You can turn off fractional character widths to fix type spacing in whole-pixel increments and prevent small type from running together. The fractional character width setting applies to all characters on a type layer--you cannot set the option for selected characters.

To turn fractional character widths on or off:

Choose Fractional Widths from the Character palette menu. A check mark indicates that the option is selected.
While recording an action, the Conditional Mode Change command lets you specify one or more modes for the source mode and a mode for the target mode.   Choose File > Automate > Conditional Mode Change
A shape layer has two components: a fill and a shape. The fill properties determine the color (or colors), pattern, and transparency of the layer. The shape is a layer mask that defines the areas in which the fill can be seen and those areas in which the fill is hidden.

After you create a shape layer (vector graphic), you can set options to subtract new shapes from the vector graphic. You can also use the Path Selection tool and the Direct Selection tool to move, resize, and edit shapes.
The Paths palette displays only two types of paths. The first type includes any vector paths associated with the currently selected Layer. The other type is the Work Path—if one exists—because it is available to be applied to any layer.
Because a vector path is automatically linked to a layer when you create it, transforming either the layer or the vector path (such as by resizing or distortion) causes both the layer and the vector path to change. Unlike a vector path, a work path is not tied to any specific layer, so it appears in the Paths palette regardless of which layer is currently selected.
Sometimes it’s possible to improve the quality of an image by blending two or more color channels. For instance, one channel in an image may look particularly strong, but would look even better if you could add some detail from another channel. In Photoshop, you can blend color channels with the Channel Mixer command in either RGB mode (for on-screen display) or CMYK mode (for printing).
 

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