Exercise 7 - Selections

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 where the image is selected.

e) Open the levels or curves palette and make a change. What happens ?
tonal range begining to degrade as the histogram is more fragmented as the original tonal range is 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 modes 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.

Exercise 6 - Basic Image Corrections

Display the Rulers. What is the keyboard shortcut ? Ctrl R

Display the Grid. What is the keyboard shortcut ? Ctrl '

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
b) What is the angle of the line ? 92.6

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 to reach both ends of the spectrum. By stretching the tonal range of the image it creates gaps ('comb' effect) along the histogram because of the limited tonal range of the original image.

What is the difference between changing the image size vs. changing the canvas size ?
changing the 'image size', resizes the image (changing the pixels ect). When changing the 'canvas size' the image quality remains the samehowever the size of the image is cropped to whatever size is requested.


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 sample image area. when it's OFF you can only repeat the area in which you have sampled.