First, duplicate the layer by dragging it down to the Make Layer icon at the bottom of the Layers palette or Command-J for the Mac, Control-J for the PC.

Then run the filter, color adjust, whatever... on the duplicate layer.

Add a Layer Mask to the duplicate layer by clicking on the Make Layer Mask icon at the bottom of the Layers palette.

Fill the Layer Mask with black from the Edit, Fill dialog or hit the D key for default colors and then press Command-Delete for the Mac, or Control-Backspace for the PC. The effect on the duplicate layer will disappear because black the Layer Mask hides imagery on the associated layer.

Finally, activate the Paintbrush and paint with white on the Layer Mask. White reveals imagery on the "effect" layer. So now you are "painting" in the effect from the duplicate layer.

For more subtle effects lower the opacity on your paint brush. To remove the effect, paint with black.

On both Mac and PC just hold down the Control key to temporarily overcome the snap.

If you work with layers much you know how easy it is to lose track of which layer an element is on. This technique helps you find and activate and element/layer by clicking on it.

First of all you can set the Move Tool's options to Auto Select Layer which will make a click on an element activate the layer. But I wouldn't advise it. Having your move tool set to auto select means that as soon as you try to move an element Photoshop activates the layer it thinks you want. This will drive you nuts if you work with transparency for reasons listed below. Here is a better way that is also one of my favorite navigation techniques.

To click find a layer; (Move's Auto Select off)

Activate the Move tool. (V) on the keyboard.

For the Mac, hold down the Control key and position the cursor over the element you want to target. Then with the Control key still held down, click-hold the mouse button and a drop down menu will appear with Photoshop's best guess listed at the top.

Now drag the cursor down to activate the layer you want. Actually, the Mac has an advantage over the PC here. You don't have to drag down to activate the first layer on the list. Just let go of the mouse button. So this means a control click-hold, let go, activates the layer. This is very fast and allows you activate layers without even having the Layer's palette open.

For the PC, hold down the Right Mouse Button and position the cursor over the element you want. Then with the Right Mouse Button still held down, click-hold and the drop down menu will appear. Now drag the cursor down to activate the layer you want.

How does it sense the Layer?

The Drop Down menu will list the layers under the cursor with an opacity of 50% and above, in stack order, under the cursor position. Layers of 49% and below are not "sensed". If you are working with layers of an opacity of 49% and below this technique will miss them.

With an understanding of how this technique senses layers it can become one of the most powerful navigation tools in Photoshop.

Link the layers you want to delete.

For Mac: Command-Option click on the Layer palette's trash icon.

For Windows: Control-Alt click on the Layer palette's trash icon.

Activate one of the type layers and then link the other type layers you want to affect.

Now hold down the Shift key and change the font, size, color, spacing, even text warping and it applies to all the linked, type layers.

A composite image in Photoshop is often made up of layers working together to create the visual composite you see. But if you want work on the visual composite as a single layer you need to Merge or Flatten the layers into one composite layer. The problem is that with Merge or Flatten you lose the independent layers that made up the composite originally.

To keep the original layers intact and produce a merged composite layer try this.

Make a new layer in the Layer stack. Make sure to leave this layer highlighted or "active". This will serve as the target of the merge.

Click the view (eye icons) on for all the layers you want to include in the merge.

Now for one of the longest key combinations in Photoshop. For the Mac: Command/Option/Shift-E and for Windows: Control/Alt/Shift-E.

This merges all the viewed layers to the active layer and leaves your original layers intact. I think of this as a target merge.
This is very handy for when you want to run a single layer operation, like a filter, on the composite of a number of layers.

Now here is a hidden one.

If you are using Layer Effects you may have noticed that they don't scale with the image when you do an Image Size. But they can and here's how.

In the Image Size dialog box you can specify the goal size/resolution in a number of ways. The trick to scale Layer Effects is to use the Resolution input to achieve your goal. For some reason Layer Effects don't scale when you use the Pixel inputs or the Width/Height inputs but if you use the Resolution input it works great.

Again, to do this you must use Image, Image Size. Near the bottom is the Resolution: input.

For some reason, when you resize an image with Layer Effects all of the other inputs will resize the image but leave the Effects unscaled. But when you spec the resize using the Resolution: input it scales the image and the Effects as well. This is an odd one but very sweet when you have a layered file with Effects that you need to scale and have the Effects come with.

Normally when you copy a selection, Photoshop copies data from the active layer only. But it can be very handy to copy what you see as a merged capture. Here's how to copy merged.

Hold down the Shift key when you Edit, Copy or for the Mac, Command, Shift-C, for Windows, Control, Shift-C.

When you Paste the result will be a capture of all the visible layers, merged, that were in your selection.

Layer Sets are a great way to organize your layers but many times you will need to merge a set to work on its component layers as a merged, single layer.

To do this, activate a layer set, go to the pop-out arrow in the upper right corner of the Layers palette, and drag down to Merge Layer Set. This will replace the set with a merged composite of the set's component layers.

But sometimes I want to get a merged version of a set to work with and maintain the set with its component layers intact.

To do this, follow the same sequence above but hold down the Option (Mac) or Alt (PC) before you release over Merge Layer Set. This will merge the set out into a new layer above the existing set rather than replacing it.

Got a soft brush and want to harden the edge fast?

With a brush tool active...

Shift-] bumps it harder in 25% increments, Shift-[ softens...