Image size, Dimension, & Resolution in Adobe Photoshop Ep4/33 [Adobe Photoshop for Beginners]


(techno music) – Hello, and welcome
to this video tutorial. Gareth here, from tastytuts.com. As you begin to create in
Photoshop, it is essential you are familiar with the
concept Photoshop uses to create images. It’s important, early
on, that you are aware so you can create the right work to the right specification. This can be a tricky concept
to understand at first, but when you do, you will
be all the more confident using Photoshop. In this tutorial, I’m going
to discuss image size, image data size, dimension and resolution. So, to begin, I’m going to dive right in and do a quick demonstration,
which you can follow along with. So let’s first open up
and image to work with. This image can be found in
the introduction folder, in the project folder. Now, you can download the
project folder for free, the download link is in the description. So, with the project folder
open, click introduction, open the ISDR folder and open the 01 image example file inside. And you should have something
that looks like this. Now, in Photoshop, we can
quickly identify the image size, dimension, and
resolution of an image, by coming up to the top
menu, selecting image, then scroll down and click image size. Upon click, up will pop a menu. This will give us the
approximate image size, dimension and resolution of the image. So, here at the top, it states the image data size and
we can see here this is 3.99 megabytes. Next, we have the dimensions
of the image, this being 1,181 by 1,181 pixels. Below this, we have the width and height. If I click the tab to the
right, and click centimeters, we can see the physical
image size is 10 centimeters by 10 centimeters. Now, if I click the tab on
the right again, and choose pixels, notice the values
are the same as above. Now here we have the option
to type in new values, should we wish to change
the image size or dimension. Now, under this, we have
the resolution of the image. Currently, this is 300 DPI
and, again, we can type in a new value and change this if we wish. So, at a glance, we can
see the image data size, the physical image size,
dimension and resolution of this image. As you begin to use Photoshop,
you will notice yourself coming in to this menu often. To check, and confirm what
size you’re working to or even change the image
size and dimension. If you wish to change the
image size, and dimension, all you have to do is
type in the new value and it will change. For example, if I change
this image from 300 DPI down to 72, Photoshop will
attempt to scale down the image. You can now see that, in the
dimensions above, it’s telling me if I press okay, this image will change from the current size,
to this new size of 283 by 283 pixels. Also, Photoshop is stating
that the image data (murmurs) will go from 3.99 megs to 234 kilobytes. Now, if I change the value
to the right to centimeters, you can see that it still
remains technically the same physical size as before. 10 centimeters by 10 centimeters. So I’ll click this back
to pixels, but this time change the width and height back to 1,181 by 1,181 pixels. Now, notice that the
resolution has remained 72. And the estimated image
size will go back to 3.99 megabytes. So, DPI did not affect the
physical image size there. So I will press cancel to close. This time, I’ll press the
shortcut for image size, command, alt and I. With the width and height values set to pixels to the right, this time I will type 500
in each box, and press ok. Upon click, the image
will decrease in size. So by coming to the top
menu, selecting image, scrolling down and clicking image size, we can check and change
the size of an image, or we can press the shortcut
key, command, alt and I. Excellent. Now it’s important to
mention that, when dealing with these principals, it
all depends on what you are creating, and what you are creating for. When working in Photoshop,
it may help to think in two mindsets. Working for print, and
working for digital. When it comes to designing
for print, you will need to pay close attention to physical
image size, and resolution. When it comes to designing
for screen, you only have to pay close attention to dimension. So, what is image size,
dimension and resolution with regards to print? To help communicate this,
you will need to open a document I have prepared
especially for this tutorial. So, back in the project
folder, open the 02 example file inside, and you
should have something that looks like this. So it will help to become
familiar with these four terminologies. We can see them up here,
to the left in this key, and each one has its own color
which is represented below. So we have image size,
image data size, dimension and resolution. So, image size is the
physical size of an image. Let’s imagine this as the
physical size it would be in your hand if you printed it out. In Photoshop, this is
measured in millimeters, centimeters and inches. Values that exist in real life. If we look at the diagram,
here we can see that each of these images are,
indeed, 10 centimeters by 10 centimeters. They are all the same physical size. Now, each centimeter is
marked out with a gray line across the left and bottom. Notice, the space that
exists between each line gets larger on 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, unlike with image size, the image data size
varies on each example. Dimension is the image size
on your computer screen. In Photoshop, this is also
measured in millimeters, centimeters and inches, but
also, importantly, pixels. If we look carefully at the
diagram below, we can see the pixel dimensions vary on each example, getting larger to the right. Next, we have resolution. This is the pixel density
contained inside an image. We learned in the previous
video that rasta images are made of individual pixels. Resolution is always measured
and referred to in DPI, dots 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 in to a physical image size. That image that you hold in your hand. If we look at the diagram
below, we can see the various DPI apply to each example. The bigger the DPI, the
bigger the pixel dimension. Now, if you were to print
each one of these images separately to their native DPI, they would all come out the same. 10 centimeters by 10 centimeters. So, if that is true, then why
do they vary in size here, visually, on the screen? Now, if you look very
closely, we can see each image has a different DPI. It’s the DPI, the resolution,
that will determine the pixel density. The larger the pixel
density, the more pixels will make up an image. Thus, the larger the
pixel dimensions will be. So, the first example on the far left, is 10 centimeters by 10 centimeters. This has a DPI of 72. Which makes the pixel
dimension 284 by 284 pixels. Now, because the DPI is
only 72, there will not be as many pixels inside
each centimeter that makes up the physical image size. The second example is
also 10 by 10 centimeters. This has a DPI of 150. Over double the previous example. This makes the pixel
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 lines are larger here, compared
to the first example. So the last example is
also 10 by 10 centimeters, but this has a DPI of
300, which makes the pixel dimension 1,181 by 1,181 pixels. Now, because the DPI is 300,
there will be a lot more pixels in each centimeter
that makes up the physical image size. So, even though the physical image size for each example is the same, the 300 DPI example contains
over three times more pixels inside, than the
first example at only 72 DPI. Now, what you will find is,
if you printed all these images off, the image at 300
DPI will be higher quality. And that is because there
are simply more pixels making up the image. The image, at 300 DPI, has
a greater pixel density than the image at 72,
allowing for more detail. So the image, in theory, is the same size but the 300 DPI has more
pixels inside the image, allowing for more detail. A good example of this,
is with new generations of digital cameras. Modern cameras today have
light capturing censors that allow you to capture
images with multiple megapixels, which enable them to
capture a lot of detail. The pictures produced will
have the same image scale and physical size as traditional images, generally six by four, but will have huge pixel
densities, allowing for immense detail. This allows you to print
out mega sharp, mega large and detailed images. Now, it’s important to
mention that DPI and dimension also affects the image
data size of an image. The more pixels you have in
your image, the more data will be contained in the image file. And we can see there, the
image data sizes are varying, getting bigger, to the right. So we can see a clear
file size difference there as more pixels are contained in an image. So, keep in mind, the difference
here between image size, dimension and resolution for print. Now, if you are creating work
for print, you will have to work to a resolution of at least 300 DPI. Print requires 300 DPI
because, essentially, this is the optimum DPI
our eyes can detect. Anything above this would be excessive. So we should send our files
to print, at a maximum of 300 DPI. If you’re 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 millimeters,
centimeters and inches. Now, for print, you could
work to a lower DPI than 300, but what you will find is
your final outcome may not be as sharp or as clear as it
would be if you were preparing your work at 300 DPI. So now we come to digital. To help communicate this,
we will need to open another document I have prepared
for this tutorial. So, back in the project
folder, this time open the 03 digital example file
inside, and you should have something that looks like this. Now, when creating artwork
and graphics for screen-based media, it is actually
irrelevant which resolution you work to. When creating media for
digital, it’s all about the dimensions. If you’re creating graphics
for websites, video or mobile devices, you
will have to work to a specific pixel dimension. In this example, I have three images. Each of these are set
at the same dimension, but have different DPIs. We can see here that the DPI
does not affect the outcome of the visual image screen size. Since this is for screen, and rasta images are made 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 dimensions and work to pixels. Now, if you are required
to create images for a Retina display, you
will usually find that the dimension of the images will
be around double the size of the normal size. So that is a brief overview
of image size, dimension and resolution. And how to view an image
size and also change it in Adobe Photoshop. In the next video, we’re going
to look at the fundamental basis of any artwork created in Photoshop. Next, we are going to learn
at how we work with layers in Adobe Photoshop. See you in the next video. (upbeat techno music)

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