The Magic of Blending Modes
Lighten and Darken
:On the right is a layers palette.  On the third row down is the blending mode dropdown box  and the opacity dropdown.  They are set to "Normal" and 100% which are the default values.
  1. Open an image that is overall too light.
  2. Create a duplicate layer named bottom then create another duplicate layer named top.
  3. Click on the blending mode dropdown box and select the "multiply" blending mode.  This will darken the entire image.
  4. You may reduce the effect of multiply (Top) layer by clicking on the opacity dropdown and moving the slider to a lower percent.  Try starting with 50% then adjusting it from there.
  5. You may show a portion of the bottom layer by adding a layer mask to the Top layer (click on the icon) then painting black on the portion of the mask you wish to block.
  6. If you open an image that is overall to dark you may lighten the image by the same steps as above except that in step 4 select the "screen" blending mode which will lighten the entire image.
Preventing Color Shifts
When the levels or contrast commands are applied the intent is to change the lightness or darkness of the image.  However these commands can sometimes change the color of an image slightly.  Also you can use the levels command to effect the red, green and blue channels individually.  This can be done to cause a desired color correction.  However it can be used to selectively change the luminosity of an image.  What is needed is the luminosity blending mode applied to an adjustment layer.  The luminosity blending mode (in either pixel layers or adjustment layers) will allow for changes of lighting to show but will not allow for any changes in color to show.
  1. Open an image
  2. Create a duplicate image named Bottom
  3. Create a brightness/contrast adjustment layer.
  4. Increase the contrast using the adjustment layer.  For many images (but not all) there a noticeable color shift.  This is especially true of images that are already well saturated.  This could cause an image to become over-saturated.
  5. Change the blending mode of the brightness/contrast adjustment to "Luminosity".  This will allow the contrast to remain but will prevent the color shift.






  
Dodging and Burning
One can lighten an image selectively with the dodge tool (grouped with the burn tool and the sponge tool.).  The burn tool can also be used to darken an image selectively.  These tools have a couple of major disadvantages.  The first is that it actually changes pixels in the layer to which it is applied.  Second, when used too much in an area it can cause that area to loose contrast and become "muddy".  By making the dodging and burning operations on a separate layer both of these problems will be resolved.  The following steps will show how this can be done.  Information on the Overlay blending mode:  Luminosity is measured on a scale from 0 (black) to 255 (white).  If a layer has the overlay blending mode it will cause the underlying image to appear darker if the luminosity of the layer has a value of less than 128 (neutral gray) and darker if the value is greater than 128.  If we start with a layer that is completely neutral gray and it has a luminosity mode of Overlay then that layer will have no effect on the image.
  1. Open an image that have light and dark areas that need to be corrected.  Create a duplicate image called Bottom.
  2. Create a new layer with the command "Layer -- New -- Layer".  Name the layer "Dodge/Burn"
  3. In the resulting dialog box use the Mode dropdown menu to select the "Overlay" blending mode.
  4. Also in the dialog box check the box labeled "Fill with Overlay-neutral color (50% gray)"  Click OK.  This will create a new layer that is completely 50% gray (luminosity value 128) and with an overlay blending mode.  At this time it will have no effect on the image.
  5. First let us lighten the dark portions of the image.  Choose the paint brush, make the foreground color white, and make the brush opacity low -- 15% to 25%.  Now with the Dodge/Burn layer active paint white over the burn layer to lighten the image.  You can make the areas even lighter by repeatedly dodging (painting white) the areas two or more times.  Note:  You must release then repress the mouse bottom to repeat a dodging operation.
  6. Now let us tackle the light portions of the image.  Do the same thing as in step 7 except that the foreground color must be black.  Then you may burn (paint black) the light areas to make them darker.
  7. If you look at the Dodge/Burn layer now you will see that it is darker on the light areas and lighter on the dark areas.  This is the effect we were seeking.
Sharpening
There are many ways to sharpen an image which should be done prior to printing.  Sharpening works by increasing the contrast along the edges within an image.  In doing so it creates some dark areas (or artifacts) and some light areas (again artifacts).  One of the biggest dangers of sharpening is over-sharpening which makes these artifacts become pronounced.  It is mostly the white artifacts that makes an image appear over sharpened.  This technique allows us to increase the sharpening without the appearance of over sharpening.
  1. Start with an image that has multiple layers.  Make the top layer active.
  2. Create a new layer by pressing shift-control-alt with the left hand and the E with the right hand all at the same time (affectionately known as claw-E)  This would create a new top layer that is the collected image of the other layers -- the same as if you flattened the image except that the layers are preserved.  Name this layer Dark Sharpen.
  3. Sharpen by using the command "Enhance -- Unsharp Mask" then setting the amount to 500, the radius to 4.0 and threshold to 0.  Two notes:  This will strongly over sharpen - that is OK.  And secondly, these numbers are just suggestions.  Different images will require different settings.
  4. Change the blending mode of Dark Sharpen to Soft Light (Overlay or Hard Light will also work.)  This will block out the white artifacts leaving only the dark artifacts to sharpen the image.  It will look like it is not over-sharpened as much but it still will likely still be too dark.
  5. Now reduce the opacity of the Dark Sharpen layer to reduce the sharpening effect.  You might start with 50% and adjust the opacity from there.
  6. You may also need to further sharpen to bring in some of the white artifacts.  Prepare for this by another claw-E (shift-control-alt-E).  Name this layer Light Sharpen.
  7. Again use the "Enhance -- Unsharp Mask" command but make the amount 75- 80, the radius about 1.5, and the threshold to 15-20.  Again, just suggestions.
  8. You are now finished.
Text Layers
Information:  
  1. Start with an image on which you wish to place text.
  2. In the tools palette make the Text tool active.
  3. From the top dropdown menu of the tool settings pick your desired font.  
  4. From the next dropdown menu pick the font size.  100 pt would be a good starting point.
  5. Click on the image where you want the text to start.  Then type your text.  Then click on the green check to accept.
  6. With the type layer active select the move tool.  Be sure to have "Show Bounding Box" checked.
  7. You may now move (position) the text box to anywhere you wish.  You may also resize the text box by dragging the bounding box points.  Click on the green check to accept.
  8. Make the type tool active.  If you click on the text you may insert or delete characters.
  9. If you select the text in the text box you may change it the text color, size, font, or font style.
  10. With the command "Layer -- Layer Styles -- Style Settings" you may apply a layer style.  A suggestion is stroke.  Make the stroke a color that contrasts with the font color.