Have you ever tried to print a photo you took or use an image in a graphic design project, only to find that it looks pixelated and blurry? That disappointing result is likely due to the image having too low of a resolution.
Luckily, Adobe Photoshop provides powerful tools to help you increase the resolution and quality of your images. By the end of this guide, you‘ll know exactly how to transform your images to look clear and sharp at any size.
What Is Image Resolution and Why Does It Matter?
Image resolution refers to the amount of detail an image holds. Resolution is typically described in PPI, or pixels per inch. The more pixels an image has per inch, the higher the resolution.
High resolution images are important for:
- Printing photos – Images with at least 300 ppi look much more detailed and less pixelated when printed, especially at larger sizes
- Graphic design – Using high res images ensures graphics and layouts will look professional and not blurry
- Editing flexibility – Starting with a higher resolution gives you more flexibility to crop and resize the image as needed
How to Increase Image Resolution in Photoshop
To increase your image resolution in Photoshop, follow these key steps:
Step 1: Open your image in Photoshop and go to Image > Image Size
Step 2: Uncheck the "Resample" box. This will lock the current pixel dimensions.
Step 3: Increase the Resolution value to at least 300 ppi for best print quality. Notice the Width and Height values will decrease to maintain the same amount of pixels.
Step 4: Check the "Resample" box to adjust the image‘s pixel dimensions. Make sure a good interpolation method like "Preserve Details 2.0" is selected. This will retain as much detail as possible while increasing the number of pixels.
Step 5: Adjust the Width and Height as needed for your desired print size or resolution. The Document Size section will show you the new file size.
Step 6: Click OK to process the image. Photoshop will create new pixels in between the existing ones to increase the resolution.
Understanding Interpolation Methods
When you resample an image to a higher resolution, Photoshop has to create new pixels to fill in the additional space. The interpolation method determines how Photoshop calculates the values of these new pixels. Here are the common methods and the results they provide:
Automatic: Photoshop chooses between Preserve Details and Bicubic interpolation depending on the image type and size difference. A good general option.
Preserve Details: Maintains edge detail while smoothing gradients. Often the best choice for upsampling.
Bicubic Smoother: Prioritizes smooth gradients over crisp edges. Works better for simple images and illustrations.
Bicubic Sharper: Keeps edges defined but can introduce stair-stepping artifacts. Useful for images with fine details.
Nearest Neighbor: Copies the value of the nearest pixel without any averaging. Maintains sharp edges but creates a more jagged, pixelated look.
Bilinear: Averages the nearest 2×2 pixel block, resulting in a smoother but softer appearance than Nearest Neighbor.
I recommend using Preserve Details or Bicubic Smoother in most cases when increasing resolution significantly. However, you may need to experiment with the different methods to see what looks best for your specific image.
Sharpening Upsampled Images
Even when using the optimal interpolation methods, an upsampled image will still look softer than one that started at a high resolution. Luckily, Photoshop provides additional tools to bring out more detail and crispness.
Unsharp Mask
Despite its name, the Unsharp Mask filter is one of the best ways to sharpen an image. It works by increasing contrast along edges. You can find it under Filter > Sharpen > Unsharp Mask.
The Amount slider controls the strength of the sharpening effect. Higher values create more contrast.
The Radius determines how many pixels along an edge are affected. Keep this value between 0.5-2 pixels for most photos to avoid oversharpening halos.
Threshold sets the minimum brightness change needed for a pixel to be sharpened. Leave at 0 to sharpen all pixels or increase to limit sharpening in smooth areas.
High Pass Filter + Overlay Blending
Another powerful sharpening technique is to use the High Pass filter on a duplicate layer with the Overlay blending mode. This increases edge contrast similar to Unsharp Mask but with a more natural look. Here‘s how to do it:
- Duplicate your image layer (Ctrl/Cmd+J)
- Go to Filter > Other > High Pass
- Choose a Radius of 2-4 pixels so the image turns mostly gray
- Change the High Pass layer‘s blending mode to Overlay or Soft Light
- Adjust the layer opacity to control the sharpening strength
Avoiding and Minimizing Quality Loss
No matter how carefully you upsample an image, some quality loss is inevitable compared to an image that started at a higher resolution. The interpolation process can only estimate what the newly created pixels should look like.
Upsampling by huge amounts will make an image look increasingly artificial. For best results, aim to upsample images by no more than 2-3 times their original resolution.
Of course, capturing or sourcing images that are high resolution to begin with is the ideal scenario. When taking photos you plan to print or use in important projects, shoot in your camera‘s highest quality JPEG setting or in RAW. For stock images or graphics, choose files that are larger than you need.
If you do need to significantly upsample a lower resolution image, consider combining multiple sharpening methods and making targeted adjustments to important areas. Converting the image to a Smart Object before applying filters will let you go back and tweak the settings.
Seeing the Difference: Low vs High Resolution
To demonstrate the impact resolution makes, here is an example of an image at a low resolution of 72 ppi versus 300 ppi. Notice how much sharper the details and edges are in the high resolution version.
While the differences are subtle on screen, they become much more apparent when printed at a larger size like 8×10 inches or used in a professional design.
Putting It All Together
We covered a lot of ground in this guide, so let‘s recap the key points:
- Image resolution is measured in pixels per inch and determines how much detail an image holds
- Use images with at least 300 ppi for the best quality prints and designs
- To increase resolution in Photoshop: uncheck resample, increase to minimum 300 ppi, check resample, choose interpolation method, and adjust pixel dimensions
- Preserve Details and Bicubic Smoother interpolation often produce the best results when upsampling
- Sharpen upsampled images using the Unsharp Mask filter or High Pass filter with Overlay blending mode
- Minimize quality loss by not upsampling more than 2-3x the original size or by starting with high resolution images
Equipped with this knowledge, you‘re now ready to prepare your images for all kinds of print and digital projects. While capturing high quality images in camera is ideal, Photoshop‘s tools can go a long way to rescue lower resolution files.
The next time you need to enlarge an image, remember to check the resolution first and follow the steps outlined here. With some practice, you‘ll be able to optimize any image to look its absolute best. Happy editing!