Having a digital lifestyle is unavoidable these days, expecially if when using photographs. You’ve taken some great photos with your phone and now you need them fro your blog, Facebook page, or Twitter feed. For most online publishing images from your phone are good to go as they are. Many social media sites now have algorithms that will process images on the fly for use in their service. But what if that image needs to be used as a print, in a magazine or book? It will need to be resized. Photoshop offers several solutions for resizing images effectively. Here’s how.
First let’s talk about what resizing is. There are two concepts to consider, resizing and resampling. With resizing, we are changing the size of the document without changing the image’s pixel count. When we resample an image, we are changing the pixel count by upsampling, make the file size bigger, or downsampling, making the file size smaller. When the camera captures an image, it will usually use the base resolution of 72ppi. However, its pixel count (megapixel) will define the image’s detail. For example, with my Evo 4G LTE that file will be 3264 x 1840 pixels. The “document’s dimensions” are 45 inches by 25 inches.
In Photoshop, to resize the image, we’ll use the Image Size command, Ctrl-Alt-I PC/Cmd-Opt-I Mac. In the dialog box uncheck Resample. Next, in the Document Size section, change the Resolution. Notice the document size will change, but not the pixel count. The same is true when we change the document size dimensions. When we resize the image, Photoshop changes the instructions for the dimensions of the image only. The original pixel information remains the same.
In Photoshop, when resampling, make sure that all of the checkboxes are checked, and use the default, Bicubic (best for smooth gradients). So, when changing the image data to a smaller resolution and document size we are throwing away data and the file size becomes smaller. This is known as down-sampling. When changing the resolution to be higher than the original and the document size is also made larger we are adding pixel data and making the file size bigger. This is known as up-sampling. Keep in mind that when adding these extra pixels we are not adding any image detail. This extra data is simply keeping the image from appearing pixelated. In fact, if care is not taken when doing this operation the extra data will begin to interfere with the original image data and degrade it. Down-sampling however, while a lower resolution or document size still removes image data too, the quality of the image, like its sharpness and contrast, is not affected visually as much.
One of the best ways to up-sample an image to maintain quality is the 10% Solution. Here’s how it works. When in Image Size dialog, be sure all Scale Styles, Constrain Proportions, and Resample Image are checked. Next, in the Pixel Dimension section, change how Photoshop will process pixel data from pixels to percentage. Then change the percentage from 100% to 110%. By using these small 10% incremental changes, Photoshop changes the original data a little at a time instead a giant one time change. This process help to preserve the quality of the original file.
To make this procedure more time efficient, assign an Action to it. If you are unfamiliar with Actions, check out my article about them here. By making an Action you can simple press a shortcut key multiple time to get to the size image you’ll need.
Check out this Social Media Cheat Sheet over at Digital Photography Review Connect site.for image size requirements of popular social media sites. When you take the time to process your images correctly for output, whether its for print or online, your images to always look great.