Getting started with photoshop.

Photoshop
Photoshop is an image editor.you can adjust the brightness,color,sharpness,the focus retouch and many more.
you  can also start with blank document and create a piece of art work .
you can also enhance artwork which are created with hand drawing.

you can make texture in photoshop and it can be later used in 3d modeling and 3d max
and Maya.
you can manipulate your image as you want.
What is RGB model.

RGB is additive color model in which red ,green and blue light are added together in various ways to reproduce colors.RGB is device dependent color model .Different devices detect or reproduce a given RGB. value differently.
Numeric representation of RGB.
MINIMUM VALUE-0(0%)
MAXIMUM VALUE-255(100%)
R-0,G-0,B-0=BLACK.
R-100,G-100,B-100=WHITE.
The three channels translate to 24(8*3)bits of color information pixel.
Opening an image.

Method 1-File-menu-open.
Method 2-start the Bridge or file -Browse in Bridge.(shortcut alt+ctrl+o)

Re crop image manually.
Rectangular marquee tool-image-crop.

Resizing an image

Method 1-Re -sampling-change the physical dimension of an image by adding or deleting pixels.
Method 2-change the resolution.

Making selection.
You cannot select an image by just clicking it.because photoshop doesn't perceive the image as an
independent object.Instead the program see pixels.it can be view when it is magnified.

SHORTCUT.
Deselect the image-ctrl+d
subtract from a selection-alt+click
add to a selection-shift+click
inverse the selection-ctrl+shift+i
hide or show the selection outline-ctrl+h
copy an intire imagectrl+a then ctrl+c
paste an image into selection ctrl+shift+v

selection method.
Selection method 1--Magic wand tool-select similar color into single click.
The tolerance value defines how many colors the wand tool selects at a time,by default it is32.

Anti alias check box to soften the selection outline just enough to make it like an organic photographic boundary.
contiguous -it make sure that the magic wand selects uninterrupted regions of the color.
Expand the selection.
1.From select-grow.
2.From select-similar.
Difference between grow and similar.
Grow select particular color up to the point it encounters non color pixels.similar selects all particular pixels within the tolerance range regardless of where they lie.
Selection method 2-quick selection tool-

The Quick Selection Tool is a relatively new tool in Photoshop that is fast and easy for selecting items.

After selecting this tool simply paint the area you want to select with the curser.  You can adjust the brush in the menu bar depending on the size and contrast of the object you wish to select.  You can change the diameter, hardness and spacing of the brush and even have the option of changing its angle and roundness.  If you need to change your brush size while making a selection, press the right bracket (]) to increase the size and the left bracket ([) to decrease it.

 

There are three selection options.  The default option is to select a New Selection.  Once you have made an initial selection, the option automatically switches to Add to Selection to increase the selection area.  If you need to deselect a portion of the selected area, choose Subtract from Selection and paint on the area you wish to deselect.

Sample All Layers allows you to select from all layers rather than just the currently selected layer.  Auto-Enhance automatically smoothes out the edges of the selection boundary.

For more control over the edge of your selection, click on the Refine Edge button.  The Refine Edge button allows you to refine your selection and view your selection against a neutral background so you can more clearly see how your selection will look.  Select a portion of your image, and then click on this button.  By default when you choose this, everything outside of your selection will appear white so you can more clearly see what you have selected.  You can then use the sliders to adjust the selection area.  Make sure Preview is checked so you can see the results of your changes. 

 

Radius controls the size of the area inside the selection boundary where the edge refinement occurs.  The higher the number the more contracted from the original selection area.  Contrast sharpens the edges of the selection.  The higher the Contrast number the more defined the edges will be.  Smooth controls irregularities in the selection boundary.  The higher the number, the more smoothed out the selection boundary will be.  Feathering the selection will create a faded transition from the selected area to the area outside the selection.  The higher the number, the larger the feathered area will be up to 250 pixels.  Contract/Expand enlarges or minimizes the selection boundary.  Positive numbers expand and negative numbers contract.  This tool in conjunction with others can help fix problems in your selection boundary.  For example, if some of the background is still visible around the edge of your selection, contract the boundary.  Below the sliders are five options that allow you to adjust how your selection is previewed with descriptions below that describe each option.