### Digital Imaging - Interactive Classroom.net

```LO: Understand how a digital image is made
up and be able to recognise the affect
changing the resolution has on an image.
Two main types:
Bitmap
Vector
We’re focussing on
at photographs.
bitmap in this topic as we’re looking
Who knows how images on a computer are made up?
Bitmap images are made up of lots of
picture elements
Also known as . . .
Pixels
Open the Pixel Drawing spreadsheet and complete the
first activity.
1 = part of the image is showing
0 = empty box
What’s happened to our image?
It is pixelated (the image is made up of
large blocks instead of smooth lines)
The same thing happens when you copy small or low
quality images from the Internet and try to enlarge them.
Who’s done that before?
Is it any better if we use 16x16 pixels?
Try the same thing on the 16x16 grid in the spreadsheet.
Any better? . . . Why?
The number of pixels we use is known as the
resolution.
So, what affect did increasing the resolution have?
On average, computer screens are 1,366 x 768 pixels
which means we can display images from the computer
using 1,049,088 pixels!
Comparing mobile phones, on which phone will pictures look
better? Why?
iPhone 5S
Resolution =
1136 x 640 at 326ppi
Galaxy S4
Resolution =
1920 x 1080 at 441ppi
Lumia 925
Resolution =
1280 x 768 at 334ppi
In a new Word document answer the following questions in FULL
sentences:
1. On which phone will pictures look better and why?
iPhone 5S
Resolution =
1136 x 640 at 326ppi
Galaxy S4
Resolution =
1920 x 1080 at 441ppi
Lumia 925
Resolution =
1280 x 768 at 334ppi
2. What does PPI stand for and what does it mean?
3. Digital cameras use the term ‘Megapixels', explain what this
means.
EXTENSION: Take a small image from the Internet and stretch it so
it becomes pixelated. Explain what is happening here.
LO: Understand how a computer displays
coloured images using binary and RGB values.
Last lesson we looked at pixels using just two colours:
1 = black
0 = white
This has a
pixel depth
of one bit per pixel.
Changing the pixel depth allows us to add more colours.
How many colours would we get if we had two bits per pixel?
01 = red
10 = green
11 = blue
-> Four colours
So are four colours enough?
NO!
Nowadays we use 24 bits per pixel to store an amount of red, an
amount of green and an amount of blue. These are combined to make
other colours:
Red = 255
11111111
Green = 103
01100111
Blue = 204
11001100
111111110110011111001100
24 bits (Also known as “Truecolour”)
1.
Open
Paint
2. Select ‘Edit Colours’ and choose a colour you like.
3. What are the red, green and blue values for that colour?
What’s this a picture of?
That is exactly how images are displayed on screens.
Here’s a microscopic picture of an iPhone screen:
Screens use coloured LEDs to display an amount of red,
an amount of green and an amount of blue.
Sound familiar?
1. Take out your mobile phones.
2. Use the camera to take a photo of your
computer screen (get as close as you can but
make sure the picture is in focus).
3. Now zoom in on the picture.
4. Can you see the individual LEDs?
In a new Word document answer the following questions in FULL sentences:
1.
What is Pixel Depth?
2.
How many bits per pixel are required for a monochrome (black & white)
image?
3.
What is the pixel depth of “Truecolour”?
4.
Which three colours are used to make all other colours on a computer?
5.
Explain the process, in your own words, of how a computer takes an image and
displays it on the screen.
EXTENSION: If an image that is 1024x768 is stored on the computer with 24
bits per pixel, how much storage space would be needed? (in MB)
LO: Understand how to combine the dodge
and burn tools along with spot removal in
Photoshop.
Your teacher would like a makeover! Try doing the
following:
Remove any spots/blemishes
Whiten their teeth
EXTENSION: Now dress them up using one of the outfits.
LO: Understand how to combine layers and
remove backgrounds to create new images.
Choose one of the animal pictures and combine it with one of
the locations to create a spoof story like one of these
examples:
Use Publisher to create a mock-up of a newspaper front page.
story relating to the picture.
LO: Know how to responsibly use online
pictures and be able to merge them together
using the clone tool in Photoshop.
Are we allowed to use any images we find online?
No, they are often copyright protected.
Who does this picture belong to? ->
You are not allowed to use the images without permission from the copyright
holder (the owner).
Be responsible and select “labelled for non-commercial reuse” when using
Another good, legal source is http://commons.wikimedia.org
Find some suitable animal pictures and combine them together
to create new animals like these examples. Use the text tools
to name the animals you have “created”.
LO: Understand how to effectively collate a
selection of images into a suitable portfolio.
Create a presentation to display the images you have created
to form a portfolio.
Beside each picture explain what the purpose was and what
tools you used in Photoshop to create the picture.
LO: Know how to put together a questionnaire
to collect suitable feedback for a portfolio
of images.
We need to collect feedback about the portfolio we have
created.
What kind of questions should we ask?
Are the images convincing?
Which image is best? Why?
Create a questionnaire with at least 10 questions to
gather useful and suitable feedback about your
portfolio.
LO: Know how to combine own ideas with
peer feedback to produce a detailed
evaluation.
• Point - State the point you are trying make. What are
• Evidence - What examples can you show to help make
your point? Maybe you could include screenshots?
• Explanation - Thoroughly explain the point, including
good and bad points where possible.
In a new Word document write an Evaluation of your portfolio of
images. This should include:
1.
Explanation of what you have done
2. Detailed breakdown of the feedback you received
3.
Detailed self-evaluation (use the same criteria as you did for your
questionnaire).
4. What went well?
5.
Even better if . . .
6.
Evaluate your experience of using Photoshop, include:
• What you found easy/difficult
• Explain the tools used
• Why was Photoshop a suitable application to use?
```