Image Resolution versus Image Size Resolution is determined by the number of pixels, or dots, in a linear inch. An image with a resolution of 72 has 72 dots in a linear inch. The higher the resolution of an image, the better the quality of image you have. The image size is determined by the resolution multiplied by the height and the width of the image. Your height and width will be determined by how you received the image, be it a camera, scan, etc. What resolution should I use? Output Device Optimum Acceptable Resolution Desktop color inkjet 330 dpi 180 dpi Professional Photo lap printer 300 dpi 200 dpi Desktop Laser Printer 170 dpi 100 dpi Large format inkjet 150 dpi 120 dpi Magazine quality 300 dpi 225 dpi Screen images 72 dpi 72 dpi Resizing an Image for Print Digital Camera file sizes will vary. The size of the image will most likely be huge in dimension; too large for normal size printers. Let s resize and image for Print. File, Open and select the file: AK 240dpi.jpg From the Image menu, select Image Size The Size of image is 46.0M The dimensions are 20.5 x 13.6 Resolution is 240 dpi Photoshop Resizing Images Page 1
Resample Image Simply put, resampling an image changes the pixels within the image, by either adding or subtracting pixels. Resampling will alter the pixels in the image, but will not change the size of the image. If you do not want to alter the pixels within the image, make sure you uncheck Resample Image: Changing the Resolution Without Changing Pixel Data: From the Image Size dialog box, deselect Resample Image Result pixel data is grayed out, pixel data is locked, which means your quality is locked. File size will not decrease, Image dimensions and pixels will change. Change the resolution to 360. Notice the document resized and the pixel data did not change. Tip: Your eyes are not going to see the difference between 240 and 300 on the screen, or between 72 and 360 for that matter. Notice the file size did not change. Change the resolution to 200 The image resized File size is still the same You can print the image from Photoshop or save it as a Tiff and print it later. Photoshop Resizing Images Page 2
How do I resize and image for the Web or email? From Photoshop open the file: AK 72dpi.jpg Select Image, Image Size Notice the size of the image. 3.66 M is kind of large for an email or a web page. Leave Resample checked or turned on. We do want to affect the pixels and reduce them in order to reduce our file size. Email: 320 x 240 pixels is a good size for an image over email Position the cursor in the Pixel dimensions area of the Image Size dialog box and change the width to 320 pixels. The height will adjust accordingly. Press Ok. Notice the image is smaller. Change the zoom level to 100% by clicking twice on the zoom tool. Photoshop Resizing Images Page 3
Save the File Size guidelines for email and web Choose File, Save for Web. In the Save for Web window, click on the 2-Up tab on the top of the window. File Format: jpg for photo Quality: Choose High for email quality You can click on the quality dropdown to adjust your quality as needed, to make your image larger or smaller. You will see the changed on the bottom of the screen. Press Ok and Save. Photoshop Resizing Images Page 4
How to Resize an Image from the Web for Print? You will find images on the web that you might need to print. Caution: look at copyright data. Images on the web are typically low in resolution and are not set up for print quality. Prior to printing the image, you need to review the image and change its resolution. Remember, when you increase your resolution, your physical image size will get smaller. File, Open, CSU from web.jpg Select Image, Image Size The Image is very small, but it is 4 x 3 We don t want to alter the quality of the image. Instead we want to increase the resolution, so the pixels will be packed more closely went sent to the printer. Deselect the Resample image. Notice the pixel dimension area is locked. Change the resolution from 72 to 150. Notice the width and height adjusted automatically and it s smaller. Bottom line, there is not a whole lot of flexibility when trying to make a web image higher in resolution for print. The physical size of the image will have to decrease in order to get print quality. Photoshop Resizing Images Page 5
How can I make my image a bit larger in size and not resolution? There will be times when you need to increase your image size, slightly, for a particular project. Open the image Open UCA.jpg Choose Image, Image Size. Make sure Resample Image is selected. Under the Resample Image checkbox, we have some options. In CS6, Bicubic Automatic is selected for us and Photoshop will determine what will work best for us based on what we are doing to the image. If you click on the dropdown, you will see some options that you can select to make sure Photoshop does what you want it to do. Change the document size Unit of Measure from Inches to Percent Change the width of document size from 100% to 110%. Note, only increase the image by 10% at a time. Press Ok. Repeat the above procedure as necessary. Note, only use this is if you are in desperate need for a larger image. Quality will not be the best, but if you only increase a couple of times, it might not be too noticeable. Photoshop Resizing Images Page 6