Sunday, May 30, 2010
Sunday, May 16, 2010
Lesson 10: 17.5.2010
Why work on layers at all?
- They do not destroy your original photo.
- You are working on top of or on copies of that photo.
- You will have more control.
- You can use blending modes to change the way layers interact.
- You can change the opacity of any effects.
- You will have or can add layer masks so that you can work selectively on your photo with any adjustments you make.
Sunday, May 9, 2010
(f) Exercise 7 - Selections
- Start Photoshop CS4 and open the document ‘Selections.jpg’
- Display the Histogram palette (‘Windows -> Histogram’
- Open the levels or curves palette (‘Image -> Adjustments ->Levels . . .’ and adjust the tonal range of the entire image, then close the palette
- Select the rectangular Marquee tool – set the feather value to 0, and the style to ‘Normal’.
- a) Select a small rectangular portion of the image and observe the histogram.
- b) Select a different area of the image and observe the histogram.
- c) Click within the selected area and drag it to a new location.
- d) What is the histogram doing ? It is changing the levels of tonal range in relation the the image area selected.
- e) Open the levels or curves palette and make a change. What happens ? The image's tonal range begins to degrade as the histogram beomes more fragmented as the image's original tonal range is being stretched across the histogram.
- f) Use the selection types buttons to add to and remove areas from the selection .
- g) Use the Shift and Alt keys to add to and remove areas from the selection.
- h) Press +D or click once in the image to discard the selection.
- i) Use the History palette to undo all the changes you have made.
- j) Set the style to fixed ratio, enter a value for width and height (eg 2 and 3), then select an area of the image.
- k) Set the style to fixed size, enter a value for width and height (eg 200 and 100), then select an area of the image
- l) Set the feather value to 25, select an area of the image and make a tonal or colour change to the image. What do you observe ? The selected area can be altered and by using the 'feather' tool it allows for a soft fade out of the alteration around the edges of the selecion.
- m) Press +D or click once in the image to discard the selection.
- n) Use the History palette to undo all the changes you have made.
- 6) Select the circular Marquee tool – set the feather value to 0, and the style to ‘Normal’.
- a) Select a small portion of the image.
- b) Press +D or click once in the image to discard the selection.
- c) Press and hold the shift key while you select a portion of the image. What happens ? The circular marquee tool can be altered in size without distorting the shape.
- d) Press and hold the shift key while you select another portion of the image. What happens ? A second circular marquee is created, and when overlapped join together to create one single selection.
- 7) Select the Lassoo tool.
- a) Select a small portion of the image.
- b) Add and subtract areas to the selection and use the feather option.
- c) Discard the selection
- 8) Select the Polygonal Lassoo tool.
- a) Select part of the image by clicking a start point and adding nodes until you click on the start point to finalise the selection.
- b) Start a new selection and use the Esc key to abort the selection before you finalise it.
- c) Start a new selection, add some nodes and then use the Delete key to backstep through the nodes you have added.
- d) Set the feather value to 2.
- e) Select the two areas of the timber wall.
- f) Use the Hue control to change the colour of the wall.
- g) Go to ‘Select->Save Selection . . .’ and save the selection as Walls.
- h) Discard the selection.
- 9) Select the Magnetic Lassoo tool.
- a) Select the grey metal roof by clicking a start point and adding nodes until you return to the start point to finalise the selection. Use the Esc key to abort, and the Delete key to remove unwanted nodes if you need to. Click on any point to force a node to be created. You may need to use the other selection tools to tidy up edges etc to make an accurate selection.
- b) Save the selection as Roof.
- 10) Select the Magic Wand tool.
- a) Set the tolerance to 32
- b) Click in the sky to select part of the sky.
- c) Hold down the shift key and click to add all the sky and clouds into the selection. Use +Z to undo the last addition if required.
- d) Save the selection as Sky
- 11) Use whichever tools you want to make and save a selection for the bricks. 12) Select ‘Select->Load Selection . . .’ and set Operation to ‘New Selection’ to reload the selection of the sky.
- a) Use ‘Select->Inverse’ to invert the selection ie the entire building will be selected instead of the sky.
- b) Save this selection as ‘Building’
- 13) Choose ‘Select->Color Range . . .’
- a) Click on the blue part of the sky and use the Fuzziness slider to select all the blue sky.
- b) Use the Burn tool to darken just the lower part of the blue sky without affecting the building or the white clouds.
- c) You can use +H to hide the selection outline while you do this. Use +H to reveal the selection outline when you have finished.
- 14) Close the document.
- 15) Quit Photoshop.
- 16) Delete the ‘Lesson 8’ folder from the desktop.
- 17) Shutdown the computer.
(f) Exercise 6 - Basic Image Corrections
Original Image
Final Corrected Image
Tasks:1) Copy the ‘Lesson 7’ folder from the server and place it on the desktop. (Remember to delete this folder when you have completed this exercise).
2) Start Photoshop CS4 and open the document ‘BadImage.jpg’
3) Rotate the image 90 degrees to orientate it correctly.
4) Display the Rulers. What is the keyboard shortcut ? Ctrl (apple key) R
5) Use ‘Photoshop->Preferences->Units and Rulers…’ to swap between cm and pixels for the ruler dimensions.
6) Display the Grid. What is the keyboard shortcut ? Ctrl (apple key) '
7) Use ‘Photoshop->Preferences->Guides, Grids, Slices and Count …’ to change the grid spacings.
8) Use the Measure tool to draw a line down the centre of the façade following the joins in the bricks. Record the following :-a) How long is the line in pixels and in cm ? 6cm, 708px(Hint: Use the info palette and the ‘Units & Rulers’ preference)b) What is the angle of the line ? 92.6
9) Rotate the image so the image is straight using ‘Image->Rotate->Arbitrary…’
10) Use the crop tool to crop out any background pixels added around the outside of the image - you will lose some of the image to do this.Note: You can use the arrow keys to nudge the selected area by one pixel at a time. Shift + Arrow key nudges by 10 pixels.
11) Open the Curves palette and adjust so the image has a full tonal range and good overall brightness (Gamma correction).What has happened to the histogram ? The avaliable tonal range has been spread across the entire spectrum in order to reach both ends of the spectrum to express pure blacks (shadows), greys, and pure whites (highlights) within the image. By stretching the tonal range of the image it creates gaps ( a 'comb' effect) along the histogram because of the limited tonal range of the original image.
12) Set the background colour to black.
13) Increase both the width and height of the image by 1cm using ‘Image->Image Size …’.
14) Undo the change in size.
15) Increase both the width and height of the image by 1cm using ‘Image->Canvas Size …’.
16) What is the difference between changing the image size vs. changing the canvas size ? When changing the 'image size' it physically resizes the image (changing the pixels/cm/inches). When changing the 'canvas size' the image quality remains the samehowever the size of the image is cropped to whatever size is requested.
17) Use the Clone stamp tool to remove the pole to the left of the tower. Turn OFF the ‘Align’ option, set the brush size to approx. 8 pixels, and ‘Alt + click’ in the sky to set the point to start copying from.
18) Use the Clone stamp tool to remove a window from the façade of the building.Turn ON the ‘Align’ option, set a soft brush with a diameter of 20pixels, and ‘Alt + click’ in the brickwork to set the point to start copying from.a) How does the behaviour change when the ‘Align’ option is turned off ? When the align option is turned ON you can reproduce the entire sample image area, however when it is turned OFF you can only repeat the area in which you have sampled.
19) Save the image as ‘MasterImage.tif’
20) Close the document.
21) Quit Photoshop.22) Delete the ‘Lesson 7 folder.
23) Shutdown the computer.
(f) Exercise 5 - File Types and Sizes
This is a formative assessment instrument
You must be rated ‘Competent’ in this assessment item.
Learning Outcomes Learning Outcome 1 - Identify and define a range of file types and describe their uses.
Tasks
1) Copy the ‘Lesson 6’ folder from the server.
2) Open the file ‘Img 1 – Ex 5 – Image.tif’ in Photoshop and do the following :-
Select ‘Image -> Image Size …’ :-
1. Width of the image in pixels - 2500 Pixels
2. Height of the image in pixels - 2000 Pixels
3. Calculate the size of the image in Megapixels - 5 Megapixels
4. What is the specified resolution of the image - 30 Pixels/Inch
5. Width of the image in cm - 21.17 cm
6. Height of the image in cm - 16.93 cm
Select ‘File -> Save As…’ and save the image in the following formats. Name the files to clearly identify them.
After each save close the image and reopen to save to the next format. Use the Finder/File Browser to record the sizes of the files created.
1) The original .tif file - 15.2 MB
2) TIF file using LZW compression - 10.6 MB
3) Photoshop .psd file - 15 MB
4) Jpeg file – Quality level 12 - 4.2 MB
5) Jpeg file – Quality level 10 - 1.9 MB
6) Jpeg file – Quality level 5 - 721 KB
7) Jpeg file – Quality level 1 - 442 KB
8) GIF file – 256 colours – no dithering - 2.9 MB
9) GIF file – 256 colours – diffusion dither - 3.5 MB
10) GIF file – 16 colours – diffusion dither - 1.5 MB
Select ‘Image -> Mode -> Greyscale’ to convert the image to a grayscale image & save as
11) TIF file (no compression) - 5.1 MB
Select ‘Image -> Mode -> Bitmap’ to convert the image to a bitmap image & save as
12) TIF file (no compression) - 754 KB
Just to post two example images from the Exercise
Here is the original image
And this is the image after it was converted to Jpeg with a quality level of 1.
It is quite hard to see the difference between the two images from the smaller uploaded files but there is a definite size difference as shown in the table.
(f) Exercise 3 - Photoshop CS4 Interface
1) Identify the following items on the diagram below :-
Menu Bar Tool Bar Options Bar
Palettes / Panels Image Title Bar Status Bar
Button Bar
Menu Bar: along the very top of screen (Photoshop - File - Edit ...)
Tool Bar: down the left hand side of the screen
Options Bar: displayed under the Menu bar
Palettes/Panels: Displayed in individual information boxes down the right-hand side of the screen
Image Title Bar: displayed under the 'Options Bar'
Status Bar: dispalyed along the bottom of the screen (right click ofr more image information)
Start Photoshop CS4. Describe three ways of starting Photoshop :
1) Clicking the Adobe Photoshop desktop icon
2) Going through the 'start menu > programs > Adobe > Adobe Photoshop'
3) Right Click an image file from a computer folder and select 'open with... > photoshop'
Open ‘Photoshop->Preferences->General …’. Turn off the option ‘Zoom Resizes Window’. Click ‘OK’ to save the change.
What are the shortcut keys for the following tools :
-Hand (or Pan) tool: H
Move tool: V
Crop tool: C
Text (Typing) tool: T
Zoom tool: Z
‘Img 1 – Ex 3 - Image-1.jpg’ and do the following :
a) What is the colour mode of the image, and what is the bit depth of the image ? (Identify two locations where this information can be found). This is an RGB 8 bit image, this information is displayed on the 'Image Title Bar' or through the Menu bar 'Image > Mode'
b) What is the zoom percentage that the image is displayed at ? 16.67%
c) Change the zoom percentage to 28%.
d) Click on the green button on the title bar. What happens ? This changes the display size of the image.
e) Fit the image to the screen. What is the zoom percentage ? 19.99%and what is the keyboard shortcut ? Ctrl 0 (zero)
f) Zoom to 100%. What is the keyboard shortcut for this ? Ctrl Alt 0 (zero)
g) What does 100% zoom mean ? This means that you are viewing the image 100% which is at its 'actual' image size.
h) What do the ‘ + ‘ and ‘ - ‘ keys do ? The '+' key zooms the image in to be viewed on a larger scale while the '-' key zooms the image out to be viewed on a smaller scale.
Using the 'Status Bar'
1) What is the image size in pixels and the image resolution in dpi ? 2020 x 2906px, 300dpi
2) What is the document size in Mb ? 16.8m
3) What do the two sizes refer to ? The number on the left refers to the prining size of the image (saved and flattened file). The number on the right refers to the file's size (including layers, channels etc.)
Press the ‘Tab’ key. What happens ? Press the “tab’ key again. This key allows you to turn on/off all of the toolbars/palettes and panels
What is the keyboard shortcut to close a document window ? Ctrl W
What is the keyboard shortcut for quitting Photoshop? Ctrl Q
Lesson 5: 22.3.2010 - Colour Basics
Knowing how colours are created and how they relate to each other lets you work more effectively in Photoshop. Instead of achieving an effect by accident, you’ll produce consistent results thanks to an understanding of basic colour theory.
Primary Colours
Additive Primaries
are the three colors of light (red, green, and blue) that produce all the colors in the visible spectrum when added together in different combinations. Adding equal parts of red, blue, and green light produces white. The complete absence of red, blue, and green light results in black. Computer monitors are devices that use the additive primaries to create color.
Subtractive Primaries are pigments, which create a spectrum of colors in different combinations. Unlike monitors, printers use subtractive primaries (cyan, magenta, yellow, and black pigments) to produce colors through subtractive mixing. The term “subtractive” is used because the primary colors are pure until you begin mixing them together, resulting in colors that are less pure versions of the primaries. For example, orange is created through the subtractive mixing of magenta and yellow together.
The Colour Wheel
If you’re new to adjusting color components, it helps to keep a standard color wheel diagram on hand when you work on color balance. You can use the color wheel to predict how a change in one color component affects other colors and also how changes translate between RGB and CMYK color models.
For example, you can decrease the amount of any color in an image by increasing the amount of its opposite on the color wheel—and vice versa. Colors that lie opposite each other on the standard color wheel are known as complementary
colors. Similarly, you can increase and decrease a color by adjusting the two adjacent colors on the wheel, or even by adjusting the two colors adjacent to its opposite.In a CMYK image, you can decrease magenta either by decreasing the amount of magenta or by increasing its complement, which is green (the color on the opposite side of the color wheel from magenta). In an RGB image, you can decrease magenta by removing red and blue or by adding green. All of these adjustments result in an overall color balance containing less magenta.
Colour Models, Spaces and Modes
A color model describes the colors we see and work with in digital images. Each color model, such as RGB, CMYK, or HSB, represents a different method (usually numeric) for describing color.
A color space
is a variant of a color model and has a specific gamut (range) of colors. For example, within the RGB color model are a number of color spaces: Adobe RGB, sRGB, ProPhoto RGB, and so on.Each device, like your monitor or printer, has its own color space and can only reproduce colors in its gamut. When an image moves from one device to another, image colors may change because each device interprets the RGB or CMYK values according to its own color space. You can use color management when moving images to ensure that most colors are the same or similar enough so they appear consistent.
In Photoshop, a document’s color mode
determines which color method is used to display and print the image you’re working on. Photoshop bases its color modes on the color models that are useful for images used in publishing. You can choose from RGB (Red, Green, Blue), CMYK (Cyan, Magenta, Yellow, Black), Lab Color (based on CIE L* a* b*), and Grayscale. Photoshop also includes modes for specialized color output such as Indexed Color and Duotone. Color modes determine the number of colors, the number of channels, and the file size of an image. Choosing a color mode also determines which tools and file formats are available.When you work with the colors in an image, you are adjusting numerical values in the file. It’s easy to think of a number as a color, but these numerical values are not absolute colors in themselves—they only have a color meaning within the color space of the device that is producing the color.
Adjusting Colour Hue, Saturation and Brightness
Based on the human perception of color, the HSB model describes three fundamental characteristics of color:
Hue Color reflected from or transmitted through an object. It is measured as a location on the standard color wheel, expressed as a degree between 0° and 360°. In common use, hue is identified by the name of the color, such as red, orange, or green.
Saturation Strength or purity of the color (sometimes called chroma
). Saturation represents the amount of gray in proportion to the hue, measured as a percentage from 0% (gray) to 100% (fully saturated). On the standard color wheel, saturation increases from the center to the edge.Brightness Relative lightness or darkness of the color, usually measured as a percentage from 0% (black) to 100% (white).
Bit depth specifies how much color information is available for each pixel in an image. The more bits of information per pixel, the more available colors and more accurate color representation.
For example, an image with a bit depth of 1 has pixels with two possible values: black and white. An image with a bit depth of 8 has 28, or 256, possible values. Grayscale mode images with a bit depth of 8 have 256 possible gray values.
RGB images are made of three color channels. An 8
bit per pixel RGB image has 256 possible values for each channel, which means it has over 16 million possible color values. RGB images with 8 bits per channel (bpc) are sometimes called 24 bit images (8 bits x 3 channels = 24 bits of data for each pixel).In addition to 8
bpc images, Photoshop can also work with images that contain 16 bpc or 32 bpc. Images with 32 bpc are also known as high dynamic range (HDR) images.