How to resize images

Lesa Snider
8 February, 2012
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As the quality of digital cameras increases, so does the volume of pixels they can capture. These days, shooting in your camera’s highest-quality mode can yield an image bigger than your printer can actually print.

While most image-editing programs are happy to resize your photo for you in their respective print dialogue boxes, knowing how to do it yourself gives you more control.

To learn how to resize those large images from your digital camera for print using Adobe’s Photoshop and Photoshop Elements, read on. Happily, the steps are exactly the same in both programs.


To begin, you need to know two numbers: The document (or rather, the print) size and the resolution. When you’re printing one photo per page, your document size is usually the same as your paper size. The second number refers to pixel size, and resolution is the measurement that controls it. The goal in printing is to make the pixels too small to be seen individually – otherwise the print will look blocky.

To do this, you increase the resolution beyond what your camera was set to (typically 72 or 150 pixels per inch, depending on the model and manufacturer). If you’re printing on an inkjet printer at home, your resolution should fall somewhere between 240 and 480 ppi if you’re using glossy or matte paper or 180 and 240 ppi for regular or textured paper.


If your image doesn’t need to be cropped, you can use the Image Size dialogue box for resizing. This dialogue box is also handy for learning how big you can print your image at a given resolution. For example, if you used a lower-quality setting on your camera, your image may not contain enough pixels for you to print an 8 x 10in (20 x 25cm) photo at high resolution.

You can summon this dialogue box in Adobe Photoshop (any version) by opening a photo and choosing Image > Image Size (in Photoshop Elements, choose Image > Resize > Image Size or press c-Option-I in either program).

The resulting dialogue box reveals all kinds of information about your photo, such as the file size (how much space it takes up on your hard drive), the pixel dimensions and – most important for print – the document size, which tells you how big the photo would be if printed at the image’s current resolution.

First, you need to lock your photo’s pixel dimensions by turning off the Resample Image checkbox at the bottom of the dialogue box. This lets you experiment with document size and resolution without altering the number of pixels your photo contains (which preserves photo quality).

Next, enter your desired document size into the width field; both the height and the resolution will change automatically to preserve the aspect ratio (the relationship between width and height). If the resulting resolution falls within the guidelines mentioned earlier, press OK and your photo will be resized accordingly. If the resolution is too low, enter a smaller document size.

Alternatively, you can enter the desired resolution and Photoshop will recalculate the document size for you.

Crop It. Click and drag diagonally over your image to draw a crop box. Click and drag within the box to move it atop your photo or drag any corner handle to adjust the box size.


If your photo needs cropping – or if you can’t get exactly the right dimensions by using the Image Size dialogue box – you can use the Crop tool and dial the width, height and resolution right into the Options bar.

In either Photoshop or Photoshop Elements, open your photo and press ‘C’ on your keyboard to activate the Crop tool. Go to the Options bar at the top of your screen and enter 10in (25cm) for width and 8in (20cm) for height (you must include the unit of measurement). In the resolution field, enter 240.

If you want to crop a photo while preserving its original aspect ratio, draw a crop box around the whole photo and then hold down the Shift key as you drag any corner handle diagonally inward. You can also use the arrow keys on your keyboard to nudge the crop box into place.

Revise the size. If your cropped image is enlarged, you've entered a physical size too large and/or a resolution too high for the number of pixels the image contains.

When you’ve got the crop box just right, press Return or double-click within the box to accept it. If your image appears to enlarge once you accept the crop, the physical size is too large or the resolution is too high for the number of pixels your image contains. In that case, press c-Z to undo the crop and enter either a smaller print size or a lower resolution or both.





Lesa Snider is the author of Photoshop CS5: The Missing Manual, co-author of iPhoto ’11: The Missing Manual (Pogue Press/O’Reilly), chief evangelist of (www.istockphoto. com/lesasnider) and founder of

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