Image size, Dimension, & Resolution in Adobe Photoshop Class 4 [Adobe Photoshop for Beginners]:

Assalam.o.Alaikum,

welcome to Tech Learning 4U

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.

S

o 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.

S

o 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 Blog, 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 Blog