Transcript Unit 27 - LO2

DIGITAL GRAPHICS
M/601/6630
LO2 - Understand types of graphic
images and graphical file formats
Learning Outcome (LO)
The learner will:
Pass
The assessment criteria are the
pass requirements for this unit.
The learner can:
Merit
For merit the evidence
must show that, in
addition to the pass
criteria, the learner is
able to:
1
Know the hardware
and software
required to work with
graphic images
P1
Describe the hardware and
software used to create
and edit graphic images
2
Understand types of
graphic images and
graphical file formats
P2
Explain how different types
of graphic images relate to
file formats
3
Be able to use editing
tools to edit and
manipulate images
P3
Demonstrate the use of
editing tools to edit and
manipulate images
M1 Use advanced
editing tools to
enhance images
4
Be able to create and
modify graphic
images to meet user
requirements.
P4
Create original graphic
images to meet a defined
user need
M2 Combine original
and edited images to
meet a user need
P5
Modify images as a result
of user feedback
P6
Explain the potential legal
implications of using and
editing graphical images
Distinction
For distinction the
evidence must show
that, in addition to the
pass and merit criteria,
the learner is able to:
D1 Evaluate how
different delivery
mediums for graphics
influence file formats
D2 Evaluate how final
images meet user
requirements
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For P2, learners should explain the different types of
file formats and how different graphical images can
have an impact on what file format can be used.
They should also explain when the different file
formats are used. They could present the evidence
in the format of a table, a presentation or report
incorporating examples of different graphical
images and the file formats that are used depending
on the use of the graphical image.
For the distinction assessment criterion D1, learners
must evaluate how different delivery mediums have
an influence over the file format that is used. This
could be evidenced in a report format which
includes screen captures or graphic images, to
illustrate the points being referenced.
Scenario
Criteria
Tasks
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Assessment
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Learners should be taught about compression techniques and how and why these
are used. This can include dots per inch and why this is used, lossy and lossless
compression and the differences between these, as well as the use of colour
models e.g. RGB and CMYB. Learners can explore different graphic types (BMP.
JPEG, GIF, PING, etc.) and where they are used (web, posters, magazines,
advertisements) to do this they could be given images and use compression
techniques, saving images in different formats and understanding naming
conventions.
They should be taught to look at file sizes and the differences between each
depending on file type and the compression types that have been used.
They should be able to look at lossy and lossless images as well as saving with
different DPI and colour modes. Learners should be looking at where images are
used in everyday life e.g. advertising and promotion from A5 leaflets through to
road side hoardings and how images are manipulated for advertising e.g. how
models are “airbrushed” so they look thinner or their skin looks better than it
actually is.
Learners should explore images on different mediums, for example the web or
mobile devices in order to understand the effects resolution size has on the
delivery medium. This will link to file size in terms of web graphics compared to
print graphics and the quality.
Scenario
Criteria
Tasks
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Assessment
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Bitmap versus vector - There are two types of images, vector and
bitmap, bitmap is images, pictures, created in packages like
Photoshop that use pixels to create the image. Vector graphics
on the other hand are mathematically calculated forms, work out
by the computer as coordinates on the screen. A Vector image
like a circle is 𝜋𝑟 2 , and oval is the same with the x and y
dimension decreased or increased. When the computer needs to
make it larger, instead of increasing the pixels, it merely changes
the parameters of the formula. Therefor the image can be printed
as large as necessary, shrunken, stretched or skewed without the
loss of quality.
More importantly the image is a series of calculations, not pixels,
therefor the amount of information and the length of time to
calculate that position is far less, takes up less room and therefor
the file size is far smaller no matter how complicated it is.
An example of a vector graphic program is Illustrator or Freehand
and can be compared to Photoshop for a lot of features, similar
layout, similar saving features, cross compatibility etc. , Setting
tonal variations, colour blends, shadows etc. are still
mathematically calculated but the programs change when filters
are used or when images are imported.
P2.1 – Task 01 – State and define the difference between Vector
and Bitmap with chosen examples.
Scenario
Criteria
Tasks
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Assessment
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Lossless Compression lets you recreate the original file exactly. All lossless
compression is based on the idea of breaking a file into a "smaller" form for
transmission or storage and then putting it back together on the other end so
it can be used again.
Lossy compression works very differently. These programs simply eliminate
"unnecessary" bits of information, altering the file so that it is smaller. This
type of compression is used a lot for reducing the file size of bitmap pictures,
which tend to be fairly bulky. To see how this works, let's consider how your
computer might compress a scanned photograph.
A lossless compression program can't do much with this type of file. While
large parts of the picture may look the same, the whole sky is blue, for
example, most of the individual pixels are a little bit different. To make this
picture smaller without compromising the resolution, you have to change the
colour value for certain pixels. If the picture had a lot of blue sky, the program
would pick one colour of blue that could be used for every pixel. Then, the
program rewrites the file so that the value for every sky pixel refers back to
this information. If the compression scheme works well, you won't notice the
change, but the file size will be significantly reduced.
Of course, with lossy compression, you can't get the original file back after it
has been compressed. You're stuck with the compression program's
reinterpretation of the original. For this reason, you can't use this sort of
compression for anything that needs to be reproduced exactly, including
executable software applications, databases and spread sheets.
P2.2 – Task 02 – Define and compare Lossy and Lossless Compression in terms
of image files with chosen examples.
Scenario
Criteria
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Assessment
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Colour models (RGB and CMYK) – There has always been two colour
models since the development of computer artistry, one developed and
used primarily for PC’s and one for Apples. When the line between the
two computer formats disappeared the choice of colour models to use
remained.
RGB (Red, Green and Blue), all three colours mixed makes black, the
absence of all three makes white, every colour in between is a
percentage of these three. What it did not define clearly was the tonal
variation in the colouring, darks and lights, focussing more on the pure
colours.
CYMK (Cyan, Magenta, Yellow and Black) was developed as a crossover
between the three primary colours. Red and Blue make Cyan, Blue and
Green make yellow etc. The K (Black because there were too many other
B’s like Blue, Brown, Beige etc.) differentiated the tones from dark to
light.
At the end of the day they both give the same results with RGB slightly
richer in purity against CMYK with a wider variety of tones. Why choose,
anything dealing with the web should always be in RGB and printed
material should be in CMYK. And printing is done in plates, CYMK
plates. See here for details.
P2.3 – Task 03 – Research and Discuss the different purposes and
benefits of colour models in defining graphic images.
Scenario
Criteria
Tasks
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Assessment
◦ Dots per inch (DPI) – this is the density of the image,
the more dots per inch, the more detailed the image
looks and the better it will print. This also means
more time to print and more ink, larger files and more
processing power.
◦ Screen resolution is set in DPI, the higher it is set the
more detailed the images are, this means better
quality but screen resolution is better than printed
resolution. A standard ink printer prints at 600dpi so
there will be a degrading of the image when it prints.
A good ink printer will print at 1200dpi and will be
slower, laser colour printers start about the same but
are faster.
◦ Screen resolutions in comparison go up to 2000dpi,
depending on the graphics card. This will mean some
loss in quality but not everyone needs to print. Very
high resolution screens are there for that detail,
archviz images, high-definition video, 3d modelling
and CAD for instance.
◦ P2.4 – Task 04 – Discuss how the density of a
output image can impact on the users picture
quality with chosen examples.
Scenario
Criteria
Tasks
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Assessment
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File formats have to be taken into consideration when working with images for numerous reasons,
most importantly being not to lose all the hard work done to make the image as good as it is.
 Jpg – This is the main image type available and uses different compression tools to reduce the
size down from its original .tif format. This flattens all layers on to one layer like a deck of
cards being photographed. There is no coming back from this as the layer information is not
saved. But it is the most compatible file format, images from the web are usually Jpg’s,
images from cameras, images scanned etc. The level of applies compression determines the
quality.
 Bmp - This is the original file format, 256 colours, uncompressed, a larger file size but
quicker to load as the computer does not need to think about uncompressing it. It is still used
for certain programs like Paint because it requires less processing power.
 Png – this is a file type that is still popular as it still maintains the layers when it is saved.
Similar to a Photoshop file but with the levels reduced to JPG layers so the overall file size is
small. Programs such as Fireworks can then open this file with the different layers and allow
the user to continue to use it. It is one of the only multilayer art packages that is openly
compatible.
◦ File conversion – this usually happens is the user has exited the program and now wants it in a
different format for a purpose like a jpg for the web or to send to an outside printer or
uploading or as a gif file for use on a webpage to link to the main image. Any stage of file
conversion will lose something in quality, nothing is ever better than the original. Two things
can be changed during this stage, file size and file type.
◦ File size – people shrink the file size for different reasons, this is called compression. It might
be to email, to upload faster, to preview or view faster on a website or computer, to reduce
down the file space or just to make it mobile compatible.
Scenario
Criteria
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Assessment
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File management and file storage is vital for the workings of graphic
formatting. Photoshop needs backup storage to save its temporary files,
the larger that storage capacity is, the quicker the program can function.
This is called the cache, without it the program stores all of the image in
memory, each layer as an independent jpeg layer that adds to the file size
before saving. The cache also hides the information under each layer out
of memory so the program functions faster. It is like holding a deck of
cards and showing five of them, the other 47 are in there and in an order
but until you look, there is no need to keep that is current memory. So the
cache saves that information until you need it.
Stored size is also important, an uncompressed Photoshop file that is
multi-layered can be several MB in size, the more layers the larger the file,
the longer it takes to open and the longer it takes to transfer. Setting the
stored location on a faster drive like an SSD and the program on the
Master Hard Drive speeds up loading simply because an SSD drive loads
faster which is why most professionals use them for file storage. This is
called the Scratch Disk.
Also finding is it important, proper folders, proper file names, proper
names for layers, all of them make the opening and using of an image
better.
P2.5 – Task 05 – Discuss the range of issues involved in deciding the file
type and management of images and how this can impact on working with
chosen examples.
File Format
File Size
File Conversion
File Management
Scenario
Criteria
Stored Size
Tasks
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Assessment
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When you select the compression level for a picture file, you are
saving your picture into a specific "format" much like you can do
with a Word document or a digital image. A Word document can
be encoded in .RTF or in .TXT, just like an image can be encoded
in .JPG or .BMP formats. Obviously, different types of encodings
are good for different applications and devices.
Uploading to the internet, emailing, sending to large or small print
and archiving all require different levels of Jpeg Compression
settings while your computer browser, an iPhone and your
selected art package have all different display expectations. And
this is why knowing a bit about your client needs when it come to
picture compression is vital to the final output. Therefor choosing
where to store and demonstrate your images will have an impact
on the codes and compression technologies used to save your file.
JPEG compression works by selecting an area that is similar to
another area and repeating it rather than storing every bit of
digital information in that area. Level 10 means no compression,
an image that is exact. Level 9 it looks at one step removed from
the colour range and repeats it through the image for areas that
are very similar, level 8 takes more area and so on. By the time it
reaches level 1, all blues will be blue, all reds will be red etc.
P2.6 – Task 06 – Discuss the purpose and need for consideration
using compression techniques with chosen examples.
Scenario
Criteria
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Assessment
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The purpose of where a graphic is due to end up is important, there are
different considerations necessary for the final output that have an impact
on the final quality and format.
◦ Use on web – these are usually stored on a page as either Jpeg or Gif
depending how large they are. A gif file is small, and sometimes animated,
usually 16 colours with little compression because the size is already
small. Jpegs are the larger image but a file that is too large will take time
to load for the intended user, too long and they go elsewhere. The more
images on a page the longer it takes to load.
◦ Use on mobile phones – icons are small and though they often have detail
they do not need much. The smaller the file size the quicker the file loads.
They do not need to be more than 1.5cm2 therefor much of the detail will
be lost anyway. Using an image to replace an icon is a waste of time and
file size.
◦ Use in interactive media – games, interactive TV, DVD/Blu-Ray menus –
These have to be richer, more detailer, better quality. They will be Jpeg
and will be saved in a format that is appropriate in size, dimensions (4x3,
16x9) and quality (Blu-Ray vs. TV standard), probably with little
compression.
Scenario
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Assessment
Similarly Printed graphics is an issue because the final output determines the company
image. Displayed print tends to be richer, the colour range brighter, the quality of print
higher in terms of DPI and lower compression levels. Magazines for instance are plate
printed rather than laser or ink which means using separation technologies, usually CMYK
plates.
◦ Advertising – Posters, leaflets, flyers and banners all have different acceptability
standards. Posters will be A3 upwards which means the file size and quality needs to be
good, flyers are A5 so the quality can be reduced.
◦ Magazines and newspapers – In newspapers and magazines they will be very high
quality prints, they will have a wide target audience and though the images may only be
seen for an instant, they have to be perfect. Printing on newspaper will degrade the
image quality because of the paper density, newsprint soaks the ink in more and lowers
the quality of the file but is mass produced and looked at less than magazines.
◦ Billboards and hoardings – These will be large, sometimes very large, therefor the
image quality needs to be as best as it can get, Vector works best at this size for
instance so company banners will be Vector. For image these will need to be printed as
separate sheets so they can be multiple images as long as the bleeding and print
margins are set.
P2.7 – Task 07 – Discuss how the intended use of graphic images can impact on the quality
and output with chosen examples.
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Use on web
Use on mobile phones
Use in interactive media
Advertising
Magazines and newspapers
Billboards and hoardings
Scenario
Criteria
Tasks
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Assessment
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Because of the different mediums on the previous page have
different intent, the size, resolution, compression, colour
depth all have to be taken into account. The larger the image
with more display space there is, the higher the resolution
needs to be.
Web delivery means taking into account how long it takes to
deliver, to upload and download (e.g. over dial up, 3G,
Broadband, high speed internet).
The size of the Magazine (e.g. A4, A5) changes the need for
image quality, a flyer can be lower grade if the image is not
as noticeable. Posters are examined more so the quality is
more noticeable but they are very specific in terms of hiding
content. A flyer will have more writing which disguises
quality, posters have more on view which allows the user to
see the image for longer.
Billboards, hoarding (ultra large images) these will usually be
seen from a distance and quickly, so the impact of the
quality is diminished but the quality of output still needs to
be good because of the size.
D1 - Task 08 – Evaluate, with a range of examples, how
different delivery mediums for graphics influence file
formats.
Scenario
Criteria
Tasks
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Assessment
P2.1 – Task 01 – State and define the difference between Vector and Bitmap
with chosen examples.
P2.2 – Task 02 – Define and compare Lossy and Lossless Compression in
terms of image files with chosen examples.
P2.3 – Task 03 – Research and Discuss the different purposes and benefits
of colour models in defining graphic images.
P2.4 – Task 04 – Discuss how the density of a output image can impact on
the users picture quality with chosen examples.
P2.5 – Task 05 – Discuss the range of issues involved in deciding the file
type and management of images and how this can impact on working with
chosen examples.
P2.6 – Task 06 – Discuss the purpose and need for consideration using
compression techniques with chosen examples.
P2.7 – Task 07 – Discuss how the intended use of graphic images can
impact on the quality and output with chosen examples.
D1 - Task 08 – Evaluate, with a range of examples, how different delivery
mediums for graphics influence file formats.
Scenario
Criteria
Tasks
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Assessment