Why do you use Alpha Channels in Photoshop?  

You can use alpha channels to make and store selections that you make with the selection tools, such as the Lasso or Magic Wand. You can also use alpha channels to edit selections.

An alpha channel is a type of mask. Masks can be thought of as selections using some or all of the 256 available levels of gray, instead of a selection outline. Alpha channels define a selection in black, white, and varying shades of gray pixels. In other words, alpha channels store selections as 8-bit grayscale images.

In alpha channels, selected pixels are white, black pixels are unselected, and anything in between is partially selected or partially unselected depending on whether you think the glass is half full or half empty.

You can create a mask by duplicating a color channel and then editing the channel by using painting and editing tools and filters. Most graphics geeks refer to this as a channel mask.

If you create an alpha channel from a saved selection, the channel most likely consists of just black or white pixels. If you have a feathered or even an anti-aliased selection, you may have a few gray pixels. If you create an alpha channel by duplicating and editing a color channel, your alpha channel most likely contains varying shades of gray pixels as well.

Source :

http://www.dummies.com/Wi leyCDA/DummiesArticle/Using-Al

Answered by Rocky at 6:14 PM on July 18, 2008

You can use alpha channels to make and store selections that you make with the selection tools, such as the Lasso or Magic Wand. You can also use alpha channels to edit selections.

An alpha channel is a type of mask. Masks can be thought of as selections using some or all of the 256 available levels of gray, instead of a selection outline. Alpha channels define a selection in black, white, and varying shades of gray pixels. In other words, alpha channels store selections as 8-bit grayscale images.

In alpha channels, selected pixels are white, black pixels are unselected, and anything in between is partially selected or partially unselected depending on whether you think the glass is half full or half empty.

You can create a mask by duplicating a color channel and then editing the channel by using painting and editing tools and filters. Most graphics geeks refer to this as a channel mask.

If you create an alpha channel from a saved selection, the channel most likely consists of just black or white pixels. If you have a feathered or even an anti-aliased selection, you may have a few gray pixels. If you create an alpha channel by duplicating and editing a color channel, your alpha channel most likely contains varying shades of gray pixels as well.

Source :

http://www.dummies.com/Wi leyCDA/DummiesArticle/Using-A

Answered by Sharad Singh at 6:02 PM on July 18, 2008

You can use alpha channels to make and store selections that you make with the selection tools, such as the Lasso or Magic Wand. You can also use alpha channels to edit selections.

An alpha channel is a type of mask. Masks can be thought of as selections using some or all of the 256 available levels of gray, instead of a selection outline. Alpha channels define a selection in black, white, and varying shades of gray pixels. In other words, alpha channels store selections as 8-bit grayscale images.

In alpha channels, selected pixels are white, black pixels are unselected, and anything in between is partially selected or partially unselected depending on whether you think the glass is half full or half empty.

You can create a mask by duplicating a color channel and then editing the channel by using painting and editing tools and filters. Most graphics geeks refer to this as a channel mask.

If you create an alpha channel from a saved selection, the channel most likely consists of just black or white pixels. If you have a feathered or even an anti-aliased selection, you may have a few gray pixels. If you create an alpha channel by duplicating and editing a color channel, your alpha channel most likely contains varying shades of gray pixels as well.

Source :

http://www.dummies.com/Wi leyCDA/DummiesArticle/Using-Al

Answered by .... ..... at 8:51 PM on July 14, 2008

You can use alpha channels to make and store selections that you make with the selection tools, such as the Lasso or Magic Wand. You can also use alpha channels to edit selections.

An alpha channel is a type of mask. Masks can be thought of as selections using some or all of the 256 available levels of gray, instead of a selection outline. Alpha channels define a selection in black, white, and varying shades of gray pixels. In other words, alpha channels store selections as 8-bit grayscale images.

In alpha channels, selected pixels are white, black pixels are unselected, and anything in between is partially selected or partially unselected depending on whether you think the glass is half full or half empty.

You can create a mask by duplicating a color channel and then editing the channel by using painting and editing tools and filters. Most graphics geeks refer to this as a channel mask.

If you create an alpha channel from a saved selection, the channel most likely consists of just black or white pixels. If you have a feathered or even an anti-aliased selection, you may have a few gray pixels. If you create an alpha channel by duplicating and editing a color channel, your alpha channel most likely contains varying shades of gray pixels as well.

Source :

http://www.dummies.com/Wi leyCDA/DummiesArticle/Using-Al

Answered by Ni .. at 9:20 PM on July 13, 2008

You can use alpha channels to make and store selections that you make with the selection tools, such as the Lasso or Magic Wand. You can also use alpha channels to edit selections.

An alpha channel is a type of mask. Masks can be thought of as selections using some or all of the 256 available levels of gray, instead of a selection outline. Alpha channels define a selection in black, white, and varying shades of gray pixels. In other words, alpha channels store selections as 8-bit grayscale images.

In alpha channels, selected pixels are white, black pixels are unselected, and anything in between is partially selected or partially unselected depending on whether you think the glass is half full or half empty.

You can create a mask by duplicating a color channel and then editing the channel by using painting and editing tools and filters. Most graphics geeks refer to this as a channel mask.

If you create an alpha channel from a saved selection, the channel most likely consists of just black or white pixels. If you have a feathered or even an anti-aliased selection, you may have a few gray pixels. If you create an alpha channel by duplicating and editing a color channel, your alpha channel most likely contains varying shades of gray pixels as well.

Source :

http://www.dummies.com/Wi leyCDA/DummiesArticle/Using-Al

Answered by Yash at 12:47 AM on July 10, 2008

You can use alpha channels to make and store selections that you make with the selection tools, such as the Lasso or Magic Wand. You can also use alpha channels to edit selections.

An alpha channel is a type of mask. Masks can be thought of as selections using some or all of the 256 available levels of gray, instead of a selection outline. Alpha channels define a selection in black, white, and varying shades of gray pixels. In other words, alpha channels store selections as 8-bit grayscale images.

In alpha channels, selected pixels are white, black pixels are unselected, and anything in between is partially selected or partially unselected depending on whether you think the glass is half full or half empty.

You can create a mask by duplicating a color channel and then editing the channel by using painting and editing tools and filters. Most graphics geeks refer to this as a channel mask.

If you create an alpha channel from a saved selection, the channel most likely consists of just black or white pixels. If you have a feathered or even an anti-aliased selection, you may have a few gray pixels. If you create an alpha channel by duplicating and editing a color channel, your alpha channel most likely contains varying shades of gray pixels as well.

Source :

http://www.dummies.com/Wi leyCDA/DummiesArticle/Using-Al

Answered by Raksha at 9:26 AM on July 07, 2008

hi there

You can use alpha channels to make and store selections that you make with the selection tools, such as the Lasso or Magic Wand. You can also use alpha channels to edit selections.

An alpha channel is a type of mask. Masks can be thought of as selections using some or all of the 256 available levels of gray, instead of a selection outline. Alpha channels define a selection in black, white, and varying shades of gray pixels. In other words, alpha channels store selections as 8-bit grayscale images.

In alpha channels, selected pixels are white, black pixels are unselected, and anything in between is partially selected or partially unselected depending on whether you think the glass is half full or half empty.

You can create a mask by duplicating a color channel and then editing the channel by using painting and editing tools and filters. Most graphics geeks refer to this as a channel mask.

If you create an alpha channel from a saved selection, the channel most likely consists of just black or white pixels. If you have a feathered or even an anti-aliased selection, you may have a few gray pixels. If you create an alpha channel by duplicating and editing a color channel, your alpha channel most likely contains varying shades of gray pixels as well.

Source :

http://www.dummies.com/Wi leyCDA/DummiesArticle/Using-Al pha-Channels-with-Photoshop-7. id-1616.html

Answered by Reeta K at 12:08 PM on June 30, 2008

Well Ekta , In graphics, a portion of each pixel's data that is reserved for transparency information. 32-bit graphics systems contain four channels -- three 8-bit channels for red, green, and blue (RGB) and one 8-bit alpha channel. The alpha channel is really a mask -- it specifies how the pixel's colors should be merged with another pixel when the two are overlaid, one on top of the other.

Typically, you wouldn't define the alpha channel on a pixel-by-pixel basis, but rather per object. Different parts of the object would have different levels of transparency depending on how much you wanted the background to show through. This allows you to create rectangular objects that appear as if they are irregular in shape -- you define the rectangular edges as transparent so that the background shows through. This is especially important for animation, where the background changes from one frame to the next.

Rendering overlapping objects that include an alpha value is called alpha blending.

For more details , Please visit the source site :

http://www.webopedia.com/TERM/ A/alpha_channel.html

Answered by Alok Gupta at 10:46 AM on June 26, 2008

well ekta, Anytime you think you may need to reuse a selection, you can save it permanently in an Alpha Channel. To do this, make a selection, choose Select > Save Selection and a dialog box will appear.

Save Selection dialog

By default the selection will be saved with the current document, but you can pull down the menu to make a new document from the selection. In most cases you will save the selection with the current document. In the Name field, you'll want to type a name for your selection so you can identify it when it's time to reload the selection.

The Operator options would be available if your document already contained an Alpha channel. You can add, subtract and intersect the selection with an existing alpha channel. Or, as usual, you can create a new channel.

An image can contain up to 24 channels, including all color channels. These alpha channels are saved even when you close and reopen an image, but only when the image is saved in a format the supports it. These include Photoshop's native format (PSD), PDF (Photoshop 6.0 only), PICT, TIFF, and RAW.

Your saved selections appear in the channels palette. To load a saved selection, you would choose Select > Load Selection (but I bet you knew that!). If your document contains more than one alpha channel you would choose the one you want from the Channel drop down menu. You can also invert the selection as you load it. If you had an existing selection already made you can use the Operation options to add, subtract, or intersect the selection. Otherwise, New will be the only available operation.

Channels Palette with two alpha channelsYou can also work with saved selections via the channels palette. Take a minute to save a few selections so you can follow along while we discuss the channel palette. To view a channel as grayscale, just click on it in the channel palette. To view the selection as an overlay with the composite image still visible, click the eyeball next to RGB and the eyeball next to the thumbnail of the channel you want to see as an overlay.

When a channel is selected in the channels palette, any editing you perform is applied only to the channel, just as if you were in Quick Mask mode. Double clicking on the channel brings up its options and allows you to rename a channel. To the far right of the thumbnail, you'll see the keyboard shortcuts for selecting specific channels. It's handy to remember Ctrl-~/Command-~ to select the RGB composite image.

You'll also notice a row of buttons along the bottom of the channels palette. These buttons allow you to load a channel as a selection, save a selection as a channel, create a new empty channel, and delete a channel. If you want a dialog box to appear so that you can name the selection when you use the button method of saving a selection, hold down the Alt/Option key when you click on the button. To create a new alpha channel based on an existing channel, drag one of the channels to the create channel button. A duplicate channel will appear which you can edit. Again, hold down Alt/Option for a dialog box. To delete a channel, drag and drop it onto the far right button with the trash can icon.

Answered by Romi at 10:45 AM on June 26, 2008

Anytime you think you may need to reuse a selection, you can save it permanently in an Alpha Channel. To do this, make a selection, choose Select > Save Selection and a dialog box will appear.

Save Selection dialog

By default the selection will be saved with the current document, but you can pull down the menu to make a new document from the selection. In most cases you will save the selection with the current document. In the Name field, you'll want to type a name for your selection so you can identify it when it's time to reload the selection.

The Operator options would be available if your document already contained an Alpha channel. You can add, subtract and intersect the selection with an existing alpha channel. Or, as usual, you can create a new channel.

An image can contain up to 24 channels, including all color channels. These alpha channels are saved even when you close and reopen an image, but only when the image is saved in a format the supports it. These include Photoshop's native format (PSD), PDF (Photoshop 6.0 only), PICT, TIFF, and RAW.

Your saved selections appear in the channels palette. To load a saved selection, you would choose Select > Load Selection (but I bet you knew that!). If your document contains more than one alpha channel you would choose the one you want from the Channel drop down menu. You can also invert the selection as you load it. If you had an existing selection already made you can use the Operation options to add, subtract, or intersect the selection. Otherwise, New will be the only available operation.

Channels Palette with two alpha channelsYou can also work with saved selections via the channels palette. Take a minute to save a few selections so you can follow along while we discuss the channel palette. To view a channel as grayscale, just click on it in the channel palette. To view the selection as an overlay with the composite image still visible, click the eyeball next to RGB and the eyeball next to the thumbnail of the channel you want to see as an overlay.

When a channel is selected in the channels palette, any editing you perform is applied only to the channel, just as if you were in Quick Mask mode. Double clicking on the channel brings up its options and allows you to rename a channel. To the far right of the thumbnail, you'll see the keyboard shortcuts for selecting specific channels. It's handy to remember Ctrl-~/Command-~ to select the RGB composite image.

You'll also notice a row of buttons along the bottom of the channels palette. These buttons allow you to load a channel as a selection, save a selection as a channel, create a new empty channel, and delete a channel. If you want a dialog box to appear so that you can name the selection when you use the button method of saving a selection, hold down the Alt/Option key when you click on the button. To create a new alpha channel based on an existing channel, drag one of the channels to the create channel button. A duplicate channel will appear which you can edit. Again, hold down Alt/Option for a dialog box. To delete a channel, drag and drop it onto the far right button with the trash can icon.

Answered by Madhurima at 1:40 PM on June 25, 2008