What You Need to Know about Image Resolution (Guest Post)
“An image is worth a thousand words” as they say. They might have less to say if the quality or clarity of an image is distracting. Powerful and descriptive images make or break the content you’re presenting. If you want to keep people’s attention, come along with me for a crash course in high-quality visuals.
Pixels: The Building Blocks
Have you ever noticed squares of color in an image like the right side of this orchid? That is pixelization. Pixels are the smallest increment of color information in a photo. The measurement of the number of dots of color in a square inch of an image is resolution.
DPI and PPI
Dots per Inch (dpi) tells a desktop printer how much color information is present in an image. The printer you’re using determines your dpi needs. Images for basic printing are usually a good quality at 300 dpi even if your printer may be capable of 600 dpi. Higher dpi bloats your print job. Do you wonder why printing is slow? Large image sizes could be your issue.
PPI or “pixels per inch” is like dpi. This resolution measure helps you understand digital images. In the 1980’s monitors were only 72 ppi. Monitors and smartphones have improved. The highest ppi some smartphones can handle is 500 ppi. Larger images are unnecessary.
Your takeaway? Don’t go lower than 200 dpi for printing or your image will be blurry. 300 ppi is a good size to aim for most uses. A photo cropped to 3 inches at 200 dpi is 600 total pixels wide and perfect for Mailchimp or most other online needs.
What about Blurry Images?
But what makes an image blurry when you tinker with its size? Keep in mind that dpi is not the same as pixel dimension. Pixel dimension is the number of pixels wide by pixels high in an image. Imagining a mosaic will help for the following three scenarios:
- A 1024×768 image is 1024 pixels wide by 768 pixels high. Imagine each pixel as square mosaic tiles. At 100 dpi, your photo is 10.24 inches wide; at 300 dpi it’s 3.33 inches wide. If you changed your image to a higher resolution, the pixels are more densely spaced…and the quality is good.
- If you increase the image size, the photo will blur. Starting with the 3-inch 300 dpi image and stretching it to 6 inches does not work. Your image still only has 1024 pixels which are now stretched.
- Editing software will allow you “to add pixels” to an image, but I don’t recommend doing this. The color information of a particular image is bound by the number of pixels already there. Converting a 100 dpi image with 1000 pixels to a 300 dpi image with 3000 pixels divides pixels into more pixels. I guarantee your software will do a terrible job choosing what colors to give to these new pixels.
If you post your images on your website, in Mailchimp or in a blog, it’s important to re-size these to keep their quality and to use space wisely. Mailchimp limits image width to 600 pixels. Large photos take up limited space in your media libraries or cause your site to load at a snail’s pace. To resize images, you’ll need the help of editing software.
Photo Editing Software
Adobe Photoshop is a robust application used for editing photos and digital artwork. You could spend a lifetime learning the intricacies of Photoshop. It’s a fantastic program if you need to get into some serious editing.
This application has a cost though. A monthly subscription through Adobe is usually about $10/month, but very worth the investment if you work with images. In that case, subscribe to Photoshop–it’s the industry standard in photo software.
If you only need to do some simple editing or don’t want to deal with the learning curve of Photoshop, consider using a simpler product. These include, but are not limited to, Photoshop Elements, Google Photos, Paint.net, and Gimp. Some of these are free (Yay!). You’ll be able to fix red eyes, straighten a horizon, or adjust the contrast or light levels of your photo.
Changing the Resolution
Search online for help for each of these applications when you’re ready to change resolution. Look for image size in their “Image” menu. In the dialogue box, you’ll see pixel dimension, width, height and resolution (or ppi). Enter the desired resolution in the space provided. Make sure you keep the proportions intact, usually through a check box. (In Photoshop, uncheck “resample” to maintain the same pixel dimension and not add pixels to your image.)
A PDF (or Portable Document Format) is the standard for sending documents to someone for printing.
If your PDF generator allows you to choose resolution when creating your file, I would stick with 300 dpi for reading or for printing. You may see a “press ready PDF” option. This guarantees the look of fonts and colors and is useful for professional print jobs.
Image is everything and the quality of images is essential to clear communication. To avoid blurry photos when resizing:
- never stretch an image, and
- keep the proportions intact.
When needed, decrease file sizes for printing and for online viewing. You will:
- Increase printing speed
- Increase page loading speed
- Avoid filling up your image library
If you do these things wisely, your images and documents will look great. You may even pick up a few compliments. Wouldn’t that be nice?
Guest Post by Mick Haupt
Mick has been on staff with Cru for 27 years. He served with the Campus Ministry for four years, The Jesus Film Project for 11 years and with the Global Leadership Office for the past 12 years.
He is passionate about photography and about the stories his photos tell. But graphic design is how he spends the majority of his time. He’d love to be a food critic but doesn’t have the time. He lives in Orlando with his wife Clarice, and two rambunctious boys.
- Find a more thorough explanation of DPI and PPI on Wikipedia.
- The University of Michigan’s document, How to Change Image Resolution Using Adobe Photoshop, explains the effects of changing resolutions. It’s useful for understanding no matter which software you’re using.
- For more information, eQuipping for eMinistry has several articles on PDF files. Sus recommends MailChimp for reading newsletters by email. It’s time to make the change from those PDF attachments for your prayer letters.