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Alpha Channels and Saving Selections:

An alpha channel is 2D information that distinguishes points of transparency based upon the pixel dimensions of a 2D image.  An alpha channel is used in practical purposes to accomplish a composite of either color, tonal or pixel texture.

The real power of photoshop manifests when the use of layers is incorporated.  What a layer allows the user to do, is to stack multiple images and or adjustments while using different degrees of transparency to create an overall effect or to a specific area which could not be accomplished when altering the image as a whole.  Even a basic lasso selection incorporates the concept of transparency because it distinguishes where an alteration will take place, and where the borders of that alteration stop.

To further understand an alpha channel, let us create a lasso selection and then save the selection (call it squiggle or circle or box, etc).  When you save a selection, it notifies you that you will be creating a new channel (please read about channels in my post here: http://housetribeca.tumblr.com/post/82410168570/photoshop-tutorial-explaining-photoshop-channels ).  Examine your Channel’s panel and notice the new channel which appears below the Blue channel.  That new Channel represents the exact shape that your selection created.  If you used any auto feathering you will notice that the shape has soft edges.

The shape that you created and then saved is now called an alpha channel (make sure you De-Select your selection before doing anything else to your image).  That alpha channel translates selection information to the viewer by displaying pixels which are 100% selected in pure white, pixels which are 100% NOT selected in pure black, and pixels are partial transparency in shades of gray.  If your lasso selection had auto feather set, you will have shades of gray around the edges of your shape rather than a hard black/white edge.

This selection information, or alpha channel can then be utilized by command clicking the black and white rectangle icon of the channel.  This selection can also be “loaded” by going to Select>Load Selection, and choosing the name of the alpha channel from the drop down list.
So in short, an Alpha Channel distinguishes transparency, and in practice is usually associated with selection information.

White = 100% selected
Black = 0% selected
Grays = 1% - 99% selected



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One can get into a very detailed conversation about Photoshop Channels, but I’m going to describe them as briefly as possible.



Photoshop Channels are composed of black and white information that determine how Photoshop will present a color image to a viewer through a color display.



     The simplest channel image would be a black and white, or gray-scale image.  It is composed of the brightest point of the image reading as pure white, the darkest point of the image reading as pure black, and everything in-between reading as some range of gray.  If we think of a gray-scale image in terms of drawing, one would start with a pure white piece of paper, and add tone to an area till that area reaches the darkest point that one’s particular media can achieve.  In this particular case, white would represent the absence of tone, while black would represent maximum tone, i.e. charcoal, pencil, paint, etc.  This particular example is only useful if we continue the explanation in terms of tone and pigment, but I will be save that for a later date.  



     Let us then transfer the concept of a gray-scale image to that of light, where black represents the absence of light, while white represents pure light at maximum brightness.  We need to refer to this example in terms of light because we are looking at a photoshop image on a light based display; meaning, the display produces a white light behind a panel of pixels.  The color display is composed of pixels and each pixel is composed of sub pixels that produce either Red, Green, or Blue color at 256 brightness levels.  Since each color has the ability to display its self any where from 0 brightness to 255 brightness, that means an individual pixel can be any variation of just under 16.8 million colors (256x256x256 = 16.777 Million). The display attempts to produce an neutral tone by having each pixel produce equal levels of brightness of each Red Green and Blue sub pixel.  This is the starting point for understanding what Channels are.  



     A color image which is displayed by Photoshop is composed of three channels, Red, Green and Blue; all displaying some level of their color from 0-255.  Let us now examine the color Red.  We would see a red pixel if that pixel were only to show red light, while simultaneously the Green sub pixel and Blue sub pixel produce no light.
Red = R 255, G 0, B 0
The color Cyan would then be the absences of Red and the presence of equal parts Green and Blue.

Cyan = R 0, G 255, B 255
The color Green would then be the presence of Green and the absences of Red and Blue

Green = R 0, G 255, B 0
so on and so forth, (please examine the attached images)



Now that being said, we understand that Red is the presences of maximum Red and the absence of Green and Blue.



This can then be presented to the photoshop user with the concept of the black/white brightness scale.  Every pixel that reads as pure Red would appear is solid white.  Any pixel that had absolutely no Red present, or appears as Cyan, would be presented as solid black.  If a pixel is not pure red, it must be any tone other than white, which then gives us a visual translation that photoshop presents us that appears as a black and white version of our particular image.  (Please examine the examples of the color dresses below.)
So, in short, a color image is composed of a Red, a Green and a Blue channel.

Each particular channel tells the viewer how intense that particular color of a particular pixel is by whether that pixel is white. 
For a display to produce middle gray, the combination of RGB needs to be 128,128,128.  Any equal parts brighter or darker, will produce a neutral gray that is brighter or darker.

An RGB image can also store an Alpha Channel which is a channel that distinguishes transparency.  I will provide a future entry to explain Alpha Channels.
One can easily create an alpha channel by creating a selection then choosing Select>Save Selection.  The saved selection will appear in the channel just below Blue. (See illustration below).

One can then activate the alpha channel or selection information by command clicking the new channel.  Notice the marching ants reappear on your image.
TIP!!!  You can also command click a color channel and select varying degrees of opacity and transparency.  Lets say you command click the Red channel on image that has a woman wearing a bright red dress.  You will then have a rough selection of the Red dress, and a partial selection of anything else that has degrees of red in it.  Pure Cyan would absent from the selection. 

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PHOTOSHOP: Tutorial: Explaining Photoshop Channels

(all photos found online without attribution)

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As one becomes more experienced in the use of Photoshop for practical retouching one will realize the need and the advantage of one tool over another.

When I first introduce my students to the spot healing brush they think of it like its God’s finger coming down and magically fixing all of the problems they have on an image.  It is not till the student learns the disadvantage of the spot healing brush and its club-like use as a tool that they begin to want more control and precision of something like the clone stamp.  Lets explore the pros and cons of the different retouching tools.
The Spot-Healing Brush: brush based tool that will sample (do not use Option-Click, just click) pixels within proximity to the spot you wish to remove, and is best used for small dots, dust and micro blemishes.   
     
     Advantage: quick and simple, very easy to use when cleaning a scan or when getting rid of tiny black heads and white heads.
     Disadvantage: can not be used on large areas because with will mush the texture together and create an odd dappled effect across your image.  Can not be used near points of high contrast because it will bleed the texture together.
     Tip: the size of the brush tip should be only slightly larger than the spot you are removing.  Too large a brush tip and you will damage essential texture.

The Healing Brush: brush based tool that allows the user to choose specifically (by Option-Clicking) which texture is sampled and blended into the spot that you wish to remove.  Works much like the clone stamp, but will blend pixel texture with current luminosity.
     
     Advantage: allows you to choose a specific area that you wish to sample from for more control over blending.  Can be used for a larger area of the image than spot-healing brush.
     Disadvantage: Should not be used for very large areas because texture will take on an inconstant look and not flow well.  Can not be used at points of high contrast, can not preserve sharp edges.
The Patch Tool: lasso based tool allows one to select a large area of texture and either drag that selection from one place to another to either relocate the texture to that spot or to use that spot as the source of the texture for the selection.  The tool will then blend the texture with the edges of the selection and keep the luminosity of that area selected.
     
     Advantage: can be used to blend texture of very large areas, helps maintain large areas of pixel texture.
     Disadvantage: must be used upon an island of texture and tone, and can not be used upon an area of multiple tonal ranges that intersect with the marching ants of your selection, i.e. you can patch-tool a tree that lays on a blue sky, only if you first remove the bottom of the tree where the sky merges with the ground.  If you do not, the color and tone will bleed from the ground into the sky.
     Tip: before deselecting, use the quick keys Command-Shift-F to bring up the Fade option so that you can fade the blend to something that may be more pleasing.

The Clone Stamp:  brush based tool that allows one to sample (using Option-Click) a specific area of pixels.  The sample can be used for a 100% 1-to-1 copy of pixels that will fade onto the spot where the brush is clicked based upon the softness or hardness of the brush edges.  The tool can also be controlled by the opacity of the brush or the blending mode of the brush.
     
     Advantage: is used for making very specific and controlled retouches.  Greatest advantage is that the user can use it to copy/clone edge texture and maintain a sharp edge and or edge contrast.  Also that it can be used to blend and smooth texture by controlling the blending mode or opacity.
     Disadvantage: takes more user control and one can easily damage texture and pixels with this tool.
     Tip: try using a low opacity and soft brush to get used to using the tool
Dodge / Burn: brush based tool that allows the user to brighten or darken the tone of pixels with out destroying pixel texture.  You can size down the brush to effect a specific pixel or small group of pixels, and adjust them here and there over the expanse of the image to have an impactful, yet subtle change of the image.
     
     Advantage: can be used to effect subtle change and maintain pixel texture
     Disadvantage: can effect color and saturation when used heavily in a specific area.  To use effectively the tool must be used at very low exposures (1-8% exposure) so not to damage the image.  The result is that it is a very slow tool to use.
     Tip: (see my previous blog entry on Burn and Dodge - http://housetribeca.tumblr.com/post/77174506688/photoshop-tool-burn-dodge

- Jeremiah Dart

If you have the need to restore your preferences to their default settings; restart Photoshop, and hold Command-Option-Shift as it loads.  A dialog window should appear, and you will have the option to delete your settings.

- Jeremiah Dart

Understanding the Burn and Dodge (BD) tool.

In its most basic form, the tool references old-school black and white dark room techniques.  Burn is used to darken a portion of the image, and Dodge is used to lighten a portion of the image.

For efficiency sake, the BD tool is far surpassed by other photoshop tools such as a curve adjustment layer used to selectively darken or lighten an area of the image.

The BD tool’s strength comes from its use in micro adjustments.   You can control the “Exposure” of the Burn or Dodge function and ever so slightly lighten or darken a select group of pixels.  In our field we find that the tool is most useful when we need to even out some texture, but keep the texture: i.e. the highlights and shadows that make up the landscape of the skin.  Skin looks like skin when photographed because it is a mountain range of peeks and valleys that light cascades across giving the appears of texture.  A case in which that landscape needs evening might be when a particular wrinkle is prominent.  If one zooms far into the image and uses the dodge tool ever so gently upon the shadows that create the valley of the wrinkle at an exposure of maybe 3% gently over and over again, one can start to lighten that valley to the point where it no longer appears as a prominent wrinkle, and the reverse can be said for the peek of that wrinkle.  The BD tool can be set to Burn and used to gently darken the highlight of the peek of the wrinkle. 

This BD technique is far superior to evening out skin and other elements over using the clone stamp because this technique will preserve texture while a clone or healing technique will create a soft blurry effect.

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- Jeremiah Dart

Open two images, one which will serve as your background, and another that will be extracted and placed onto your background image as a floating layer.

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Choose your subject image and click Select > Color Range

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You will want to “Select” using sampled colors.  Notice the drop down menu.  If you look at the bottom of the interface is the drop down menu called “Selection Preview.”  Grayscale will provide you with a preview of what the color range will select.  Keep in mind that under Grayscale, White represents what is selected and black what is not selected.  Any tones in between will be a partial or transparent selection.

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Use your eyedropper cursor to select the white area of the image.  

Now bring your attention to the “Fuzziness” slider.  If you drag it to the left or right it will select either more or less pixels which are similar to the pixels that you clicked on.  Since we have clicked on the white background it color range will also pick the bright pixels of our subject if the fuzziness slider is too far to the right.

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Notice that the highlights in our subject have disappeared from our selection.  We now have a much more accurate selection which will be used to extract the subject from the white background.

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Let us now look at the “Selection Preview” drop down menu and try out some of the options.

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Once you hit OK, you will have “marching ants” surrounding our white background.  Please note that this is a selection of the white, not of the subject.  We must inverse the selection.

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Marching Ants are only around the subject now.

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Lets make a copy of this selection of the layer using Layer Via Copy

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Notice the second layer.  Let rename it to Comp Element.  This will be dragged onto our “Background Scene” image.

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Just drag the layer onto the background image.

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Let us now “Refine” our selection.

Hold the Command Key and click the “Comp Element” layer.  Notice that the marching ants appear again.

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Click the “Add Layer Mask” icon on the bottom of your layer’s panel.

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Notice the mask

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Now Right Click the mask icon and choose “Refine Mask”

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Familiarize yourself with the interface.

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Notice the View Modes.  For this case, viewing “On Black” will give us the best preview of our selection edges.

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Lets make some adjustments to the Radius, Feather and Shift the edge to the left so eliminate some of the white halo pixels.

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Hit OK and notice our cleaner mask.

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Feel free to position your subject layer into a better position.  You may also transform the subject to resize or reshape it so that it better matches your background image.

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Now lets take advantage of our layered subject and alter the contrast using a clipping mask of a curve adjustment layer.  We will increase the white point and black point to better match the contrast of the background image.

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Drag the white point to the left to increase the luminosity of the image.

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Create a second curve to adjust the black-point.

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Clip the adjustment layer to the subject layer, and drag the black point to the right to give the shadows more snap.

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- Jeremiah Dart

Didn’t know if you caught it in PDN or at the Photo Plus Expo, but HOUSE did the retouching on the images for Canon Professional Services (CPS)

Marcus Bleasdale and Gabrielle Revere photographed. Both successful photographer.

Welcome Spring 

it’s still cold here in NYC, but that doesn’t stop fashion from releasing their spring collection. We retouched the Women/Men Esprit Spring Campaign. Check it out here

Photographed by Dario Catellani

Photographer Jason Nocito (tumblr) does the Cover for Bloomberg Businessweek Magazine.
David Stern Passes the NBA to Adam Silver.

Photographer Jason Nocito (tumblr) does the Cover for Bloomberg Businessweek Magazine.

David Stern Passes the NBA to Adam Silver.

Scott McDermott Photography

Portrait of Pittsburgh Steelers Troy Polamalu

Retouching by us!

It’s a little late but Happy Holiday’s from HOUSE.

Photo Plus Expo: Canon Booth

We did all the retouching for the Canon display at PPE!

Hope you all had a chance to go and check out the new gear.

Tracy Williams LTD Presents 

DOMINGO MILELLA 

November 1 - December 21, 2013 

Reception: November 1, 2013 from 6-8 pm 

Check out the show!

Image: Tomb of King Midas,  Turkey,  2011,   C-print,   91 3/8 x 72 7/8 inches

Andrea Meislin Gallery presents Angela Strassheim, “Story Telling”

HOUSE made a few of the prints for the show.


Check out her exhibition: September 12 - October 26, 2013