It will help to be familiar with these four terminologies.
Each one has its color which is represented as above. We have image size, image
data size, dimension and resolution. So, image size is the physical size of an
image. Let image this as the physical size would be in your hand if you printed
it out.
In photoshop, this is measured in mm, cm and inches value
that exist in real life. If we look the above diagram here we can see that each
of the images are indeed 10 cm by 10 cm. They are all same physical size. Now
each centimeter is marked out by grey line across the left and bottom. Notice
the space that exists between each line get larger in each example towards the
right. Now keep this in mind image data size is the file size on your computer
hard drive. If we look carefully we can see we can see unlike with image size
the image data size varies on each example. Dimension is the image size on your
computing screen. In photoshop this is also measured in mm, cm and inches but also
importantly pixels. If we look carefully at the diagram above we can see the
pixels dimension vary on each example getting larger to the right. Next, we
have resolution, this is the pixel density contained inside an image. Raster
images are made up of individual pixels. Resolution is always measured and
referred in Dpi (dot per inch). This is the number of pixels that are contained
in each inch of an image. So, dpi is the amount of pixels that are squeezed
into a physical image size that image that you hold in your hand. If you look
at the diagram above we see the various dpi apply to each example, the bigger
the dpi the bigger the pixels dimension. Now if you want to print each of the
image separately to the native dpi they would come out the same 10 cm by 10 cm.
So, if that is true then why did they vary in size visually on the screen. Now
if you look very closely, we can see each image has its different dpi. It’s the
dpi the resolution that would determine the pixels density. Larger the pixels
density the more pixels will make up the image thus, the larger the pixels
dimension will be. So, the first example on the far left is 10 cm by 10 cm,
this has a dpi of 72 which make the pixels dimension 284 by 284 px. Now because
the dpi is only 72 there won’t as many pixels inside each centimeter that makes
up the physical image size.
The second example is also 10 by 10 cm. This has a dpi of
150 over double of the previous examples. This makes the pixels dimension 591
by 591 pixels. Now because the dpi is 150, there will be more pixels in each
centimeter that makes up the physical image size. This is why the space between
my centimeter line are larger here as compared to the first example. So, the
last example is also 10 by 10 cm but this has a dpi of 300 which makes the
pixels dimension 1181 by 1181 px. Because the dpi is 300 there will be a lot
more pixels in each centimeter that make up the physical image size. So, even
though the physical image size for each example is the same the 300dpi example
contain over 3 times more pixels inside than the first examples at only 72 dpi.
If you printed all these images, the image at 300 dpi will
be higher quality that is because there are simply more pixels making up the
image. The image at 300 dpi has a greater pixels density than the image at 72.
So, the image in theory is the same size but the 300 dpi has more pixels inside
image allowing for more details. A good example of this is with the new
generation of digital cameras. Modern camera today has light capturing sensors that
allow you to capture images with multiple megapixels which enable them to
capture a lot of details. The pictures produced will have the same image scale
and physical size as traditional images generally 6 by 4 but will have huge
pixels density allowing for immense details. This allows you to print out mega
shop mega large and detail images. It is important to mention the dpi and the
dimension also affect the image data size of an image. The more pixels you have
in your image the more data will be contained in their image file. We can see
the image data size is varying getting bigger to the right and can see a clear
file size difference there as more pixels are contain in an image.
If you are creating work for print you will have to work a
resolution of at least 300 dpi. Print requires 300 dpi because essentially this
is the dpi that our eye can detect. Anything above this will be excessive so we
print at a maximum of 300 dpi. If you are preparing work for magazines or
leaflets, you will be working to the physical image size of around A5, A4, A3
and so on or to a custom size in mm, cm and inches. You could work to a lower
dpi than 300 but what will you find your final outcome may not be as sharp or
as clear as would be if you are preparing your work at 300 dpi.
When creating artwork and graphics for screen-based media it
is actually relevant which resolution you work to. When creating media for
digital it’s all about the dimension. If you are creating graphics for website,
video or mobile devices you’ll have to work to a specific pixel’s dimensions.
In these examples, I have three images. Each of
this are set at the same dimension but have different dpi. We can see here that
the dpi doesn’t affect the outcome of the visual image screen size. Since this
is for screen and raster images are made up of pixels it’s only the dimension
of the pixels that will determine the image size outcome on the screen. If we
are preparing work for screen, we should always request the dimension and work
to pixels.
Now if you are required to create images for retina display
you will usually find the dimension of the images will be around double the
size of the normal size.
This is dummy text. It is not meant to be read. Accordingly, it is difficult to figure out when to end it. But then, this is dummy text. It is not meant to be read. Period.
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