There are many reasons you may want to change the image resolution. You may want to make a large print of an image. Or you may want to downsize an image to post on social media.
Either way, Adobe Photoshop makes it easy to change the resolution of an image.
In this article, I’ll show you how to change the resolution of your image in five easy steps.
What Is Image Resolution?
Resolution is the number of pixels in dimensions of height and width.
Your camera will produce images of a certain size depending on its sensor size.
For example, the manual of my camera says that the image resolution is 8256 x 6192 (W x H) pixels. That means the total pixel dimensions are 8256 x 6192 = 51,121,152. Divide that number by one million. The result is the number of megapixels the camera has. In my case that’s 51MP.
If you crop an image, you are taking out pixels so an image will have a lower resolution than your camera is capable of producing.
It also describes the resolution. More pixels in an image mean high resolution. This is because pixel information is denser.
High resolution gives you more detail and better image quality. This means you can print larger. The result will be smooth, continuous tones and colour transitions. But it usually results in a larger file size.
The resolution of an image is measured in DPI or dots per inch or pixels per inch (PPI). The more dots (or pixels) you have per inch, the higher the resolution of your image.
How to Select the Appropriate Size
Before I show you how to resize your images, let’s briefly talk about how large or small you’d like to make your images.
You can take a low-resolution image, one with few pixels, and increase the resolution. But there will be a limit.
If you try to increase the image too much, it will become pixelated. This means you can start to see the individual dots that make up the image. It all depends on the amount of detail in the image and the purpose of it. It takes some practice and trial and error to know how far you can go.
For instance, if I’ve cropped in a lot on an image, this will lower the number of pixels in my image. But I may want to make a large print of this image.
There are charts online to help you figure out how large you can print an image. I use this nice little tool over on Vivyx Printing.
On the flip side, you may want to decrease the resolution of your images before putting them online. This helps your images load faster. You’re also not giving out your full-resolution image that others might want to use without permission.
A good rule-of-thumb is to post images no larger than 2000px on the longest end no larger than 1MB. But each social media site has its own recommendations. This website will help you find the right size for the different platforms.
How to Change Image Resolution in Photoshop
It is easy to increase or decrease image resolution in Adobe Photoshop. Let me take you through the steps.
Step 1: Finding the Image Size
First, find the size of your image by opening the image size dialogue box.
Go to Image > Image Size… or use the shortcut Opt + Cmd + I (Alt + I for Windows).
In this dialogue box, you’ll find your image size. You’ll see a width and height pixel dimensions.
Adobe Photoshop will default to giving you the size in pixels, but you can change it to inches, centimetres, or even a percentage. Your original image will be 100%. At the top, you will see the file size of your image.
We’re going to use the tools in this window to change the resolution of your image.
Step 2: Changing the Image Size
There are a few options to change the resolution of your image.
If you’re printing, you can pick one of the presets based on standard paper and print sizes.
Click the ‘Fit To‘ drop-down menu to pick a document size.
If you’re posting the image online, you don’t need to stick to standard print sizes. Usually, it’s better to set the size yourself. Simply type in the size you want over the current size.
By default, Photoshop will constrain the aspect ratio. If you enter a number to change the width, Photoshop will automatically change the height to keep your image looking the same.
If you want to change width and height pixel dimensions independently, click on the icon that looks like a chain linking the two dimensions. This tells Photoshop not to constrain aspect ratio.
Type the number of pixels you want in the ‘Height’ or ‘Width’ box.
When you change your image size notice the number at the top of the dialogue box showing file size will change. This is the document size of your image in MB.
Step 3: Resolution
The image resolution box sets the number of pixels per inch. Everybody says this number has to be 300 pixels per inch to print the image, but that’s not exactly true. 300 DPI is the standard used for printing images. But online images can only be displayed at the resolution of the computer screen. Most screens are 72 DPI.
You can leave this number as it is. It won’t matter to online images if they are 300 or 72 DPI.
Changing the DPI will change the image size. If your image is 300 and you change only the DPI field to 150, your image will be half the size. It will also change your document size.
Step 4: Selecting a Resampling Mode
The resampling mode decides which algorithm Photoshop will use to add new pixels. There are two good options for increasing the resolution: ‘Preserve Details’ and ‘Bicubic Smoother’.
I find that ‘Bicubic Smoother’ gets the best results. You can try both the see the difference.
Here’s a comparison of all the resampling modes.
Tick the ‘Resample’ box and select a resample mode that works for you.
Step 5: Sharpening the Image
It’s always a good idea to sharpen after you increase image resolution or for online viewing.
Go to Filter > Sharpen and select ‘Unsharp Mask’.
Drag the Amount slider to 100% and the Radius to 1.0. That’s a good setting to start with when enlarging an image.
You can add more or less sharpening if the result doesn’t look right.
Adobe Photoshop makes it easy to increase or decrease image resolution. It does a good job of increasing the resolution of an image, but there are limits.
The quality and size of your starting image will decide if you’ll get good results. For example, a picture with pixel dimensions of 100 x 100 at 72 pixels per inch can’t be resized to 3000 x 3000 at 300 pixels per inch and look good. That’s just too much to ask.
It also depends on the purpose of the image. Do you need a high image quality gallery print or a banner to hang against the wall? An image for a banner doesn’t need a super high resolution to look good. Always ask the printing studio what minimum resolution they need.
It’s always best to start with a good image that doesn’t need much editing. Why not try out our Photography for Beginners course to learn how to take high-quality images every time?