Benefits
of the plugin

Transparent background or foreground color
Make any brightness range transparent
Fade-out the transparency.
Use for graphics, gifs etc.
Use for correction layers

The transparency filter plugin works with these image modes (Windows and Mac)...
8 & 16 bit / channel: RGB.

Transparency
filter controls

This is the transparency plug-ins control panel at one third size. Click on the photo or the links to see the plug-in at full size.

The filter has these sets of controls:

1. Transparency area
2. Transparency in brightness range
3. Transparency in fore- or background.

Example -

The transparency plugin is a powerful filter for making transparent backgrounds as well as making any other limited color, area or brightness range transparent. Here we made the blue sky transparent.

The Make transparent control-group

Make transparent

This control set determines which brightness areas should be made transparent.

Lights - Make white fully transparent end diminish transparency towards black.
Darks - the reverse of above.
Within limits and Outside limits - the limits are set by the next control set.

Brightness range

Brightness range

If you select within limits or outside limits, this control panel will become active.

If you select within limits, only pixels brighter than dark limit and darker than light limit will be changed.

If you select outside limits, only colors darker than dark limit and brighter than light limit will be changed.

Target is only functional if softness is set higher than 0. Target sets which brightness value is to be changed the most. Depending on the setting of softness, brightness values brighter or darker than the target will be changed in lesser degrees.

Softness

This is an excellent tool for retouching lights, mid tones or darks. If you place a monochrome layer underneath, you can tone the lights or darks with that.

Transparent mask

This lets you target two colors for transparency: The foreground color and background color selected in the host application.

In addition you can either enable or disable all the above controls for targeting a brightness range.

Spread selection

If you set spread selection to 0, only the exact color will be made transparent. As you raise the slider, more and more neighboring colors will be included.

Example

Here's the original image with a flat blue sky we want to replace with a more dramatic sky.

And this is what we want to end up with.

A keen eye will notice the light and shadows on the mountain can't be from the same light source as the light and shadows on the clouds. You can utilize this to give the image a subliminal eerie feeling like in this instance, or you can carefully select your two images so the light source is identical.

First we have to make the sky transparent. One way to do this is by setting the foreground color to the color of the sky before invoking the plugin. Click on the top square to activate the color picker, then simply click in the sky.

Then in the plugin activate the Transparent Mask > Foreground Color option to make all colors similar to the foreground color transparent. Move the spread
selection slider until the entire sky is transparent.

In this case you can also select the sky by using the plug-ins brightness-range controls, since the sky is brighter than everything else in the picture.

Remember you can't make the background layer transparent, so you have to make a new layer. In the menu "Layer" select "New" and then "New layer from background". Or as a fast shortcut: select all, copy and paste...

Then get the image you want to put instead of the blue sky. Select all, copy and paste it onto the mountain image.

At first it will be on top of the mountains, so we have to change layer order...

Changing layer order in Photoshop...

Simply left click on the top layer and drag it below the layer you want it to be placed under.

If this palette isn't visible you can get it in menu Window > Show Layers.

You should end up with this...