Image Size changes the actual image dimensions and resolution, while Canvas Size adjusts surrounding space without altering the image. Image Size affects pixel count, document size, and resolution, making it crucial for print or web use, and can cause blurring if enlarged too much without resampling. Decreasing size discards pixels, and print requires 300 DPI versus 72 DPI for web. To resize, go to Image > Image Size, uncheck Resample, and adjust width or height. Canvas Size adds or reduces empty space around the image, useful for layouts, collages, or adding margins, with new areas filled by background color or transparency. Use the anchor grid to position the image when changing canvas size, and remember that cropping removes parts of the image, while Canvas Size only shifts spacing. Use Image Size for output-specific resizing and resolution adjustments, and Canvas Size for layout flexibility without scaling the image itself.

When working in Photoshop, understanding the difference between "Image Size" and "Canvas Size" is key to editing your files without confusion. The short version: Image Size changes the actual dimensions and resolution of your image content, while Canvas Size adjusts the space around your image without altering the image itself.

Let’s break it down into more practical terms.

What Happens When You Change Image Size

Changing the Image Size affects the pixel dimensions, document size (like in inches or centimeters), and resolution (DPI or PPI) of your image. This is important when preparing images for print or web use.

• If you increase the pixel dimensions too much, especially without resampling, the image can get blurry.
• Decreasing the size usually looks fine because Photoshop discards extra pixels.
• Resolution matters most for print — web images typically stay at 72 DPI, but print might require 300 DPI.

For example, if you're resizing a photo from 4000x3000 pixels to 800px wide for a website, you’ll adjust the Image Size and probably turn off resampling to keep quality intact.

Here's what to do:

• Go to Image > Image Size.
• Make sure "Resample" is unchecked if you want to preserve original pixel data.
• Adjust width or height, and watch how the resolution or pixel count changes.

How Canvas Size Works Differently

The Canvas Size doesn’t change the image content itself — instead, it gives you more (or less) room around it. Think of it like changing the size of a picture frame without touching the photo inside.

You might use this when:

• Adding extra background space to fit text or other design elements.
• Cropping unevenly and needing to reposition the image within a new boundary.
• Creating collages where spacing between images matters.

If you expand the canvas, Photoshop fills the new area with the background color or transparency, depending on your settings.

To try it:

• Go to Image > Canvas Size.
• Enter new dimensions — you can choose relative or absolute values.
• Use the anchor grid to decide where your existing image appears in the new canvas.

A common mistake is confusing this with cropping — remember, cropping removes parts of the image, while Canvas Size just adds or trims empty space.

When to Use Which

Use Image Size when:

• You need to resize for specific output (like uploading to a site that requires exact pixel dimensions).
• Preparing an image for print at the correct resolution.
• Checking or adjusting file size for performance.

Use Canvas Size when:

• You’re designing a layout and need more breathing room.
• Aligning multiple images side by side without scaling them.
• Creating borders or margins manually.

One tip: always double-check which one you’re using — they sound similar but do very different things.

So yeah, the main thing to remember is that Image Size changes the image itself, while Canvas Size just changes the space it lives in. They both have their place, but mixing them up can lead to unexpected results — especially if you're trying to maintain quality or layout.

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