Resizing Images

Resizing your images is sometimes crucial for printing, presentations, or building websites.  Photoshop provides tools that won’t distort your images, and will keep file sizes low while preserving quality (and is heavily used on campus as well).  While there are other programs that claim similar features and results, few offer the same power, options, or flexibility of Photoshop, and UCDavis offers limited support for other imaging programs.

  1. Resizing Images for the Web or PowerPoint.
    1. In Photoshop, open the image you wish to resize.

    1. On the menu bar along the top of the Photoshop, click on “Image > Image Size”.


    1. You will be presented with the Image menu box (as shown below).


      1. From this menu you can resize the image by changing the values as shown above.  The first two rows of numbers describe the image’s width and height in pixels (pixel: one of the many tiny dots that make up the representation of a picture in a computer's memory).  By changing the dimensions with pixels, you have exact control over how big the image is when viewed at 100%; when viewing images at 100%, you are viewing the image at the highest magnification the image can display before it distorts.  If you view your image at a higher/lower zoom, you aren’t getting an accurate depiction of image size.  Generally, for images that will be used online or in a PowerPoint presentation, you’ll want your image size to be at or near typical screen resolution.  Generally accepted screen resolution is 1024x768, but keep in mind that you’ll want your PowerPoint image to occupy slightly less than the full slide area (to prevent parts of the image from being clipped off by the projector)



      1. If you’re trying to achieve the same quality in your prints that you see on your screen, you typically want to disregard how large your image looks on your screen unless you are in the print preview options.  Remember: because an image is large on the screen does not necessarily mean that it will be that large on paper.
    1. When you resize your image, make sure that the checkboxes “Scale Styles”, “Constrain Proportions”, and “Resample Image” at the bottom are checked, and change the width and height to the specifications you need. 
        1. *NOTES*
          1. Typically you are able to make a photo larger by as much as 20% without significant visible degradation. Usually, however, 10% is the farthest you would want to go for higher quality images.  (Theoretically of course, you can make an image much larger; however, pixelization will start to occur.)  Making a picture smaller has no effect on its visual integrity (unless you try to make it large again, which causes pixelization).  Always save your resized file as a copy, or as a new file.

  1. Resizing for printing:
    1. When resizing images for printing purposes, you need to take into account your printer’s capable printing resolution, as well as the size of your paper you are using.  The numbers in the document size (the next two rows of numbers) are currently how large the image is at the current resolution (the fifth row) you will be printing at.  First to resize the image, make sure that you uncheck Resample Image


    1. At default, most web or computer based images have a resolution of 72 pixels per inch (ppi) unless otherwise specified to be higher.  Typically, good photo printers output at 300 dpi or greater (this is also a good default resolution to print photos at should your printer support higher resolutions).  If you are creating an image, you might want to set the image to 300dpi.  However, your image will print at a smaller size as a result (more pixels per inch result in a smaller perceived image).  In the images above, width and height in pixels are identical, but their print size is different.
Prepared by the ET Partners Program, IET Mediaworks and UC Davis