Because of the prevalence of high-DPI screens, marketers need to use retina images to ensure that their emails look crisp and not cheap. However, that doesn’t mean that every image in an email needs to be a retina image.
Marketers should use retina images in their emails only when it creates a significantly better experience in terms of readability or impression. Otherwise, they should avoid them.
We’ll explain exactly why that is and exactly when to use retina images, but first let’s be clear about what we mean by a retina image.
The first high-DPI screens were Retina Displays created by Apple, which is why we refer to images optimized for high-DPI screens as retina images. High-DPI screens have four times as many pixels as the previous generation of screens.
As a result, for an image to display as crisp as possible on a high-DPI screen, marketers need to create images that are twice as wide and twice as high as the size that they want them to be displayed in the email.
For instance, if you want to create a 100-by-100 pixel retina image for an email, you’d create that image at 200-by-200 pixels and then define the width and height in the <img> tag as being equal to 100.
“While retina images look great, they don’t always make the most sense to use across the board,” says Kathryn Alva, Associate Creative Director for Creative Services at Oracle Marketing Cloud Consulting (OMCC). “That’s because they take more time and effort to create and they increase file sizes significantly, which increases email load times.”
Compressing retina image files helps, but only to an extent. For that reason, you want to be judicious in your use of retina images.
We recommend using retina images for:
“Essentially, it’s all the stuff that’s built into your email template,” says Patrick Colalillo, Associate Creative Director at OMCC Creative Services. “Anytime there’s text, a symbol or logo, or another high-contrast element like that in an image you should seriously consider using a retina image to ensure that those elements have crisp edges and look sharp.”
We don’t recommend using retina images for:
“While the increased clarity between non-optimized and optimized image text, logos, and icons is noticeable and has a minimal impact on file weight,” says Alva, “the visual difference between non-optimized and optimized lifestyle images is minimal and has a significant impact on file weight.”
For example, in the image below, the retina version of the image on the right has a file size that’s more than seven times the non-retina version. However, the difference in picture quality is almost unnoticeable.
Admittedly, you may encounter some cases where an image you want to use in an email doesn’t fall nicely into one of those two buckets. Perhaps you have a hero image or some smaller secondary images with a few small high-contrast elements and you’re unsure whether a retina image is appropriate.
In those cases, we recommend doing an A/B test of a retina image versus an non-retina image. If you have a large enough send, you can do a 10-10-80 test where you test the retina image on 10% of your audience and the non-retina on 10%, and then send the winner (based on clicks or, even better, conversions) to the remaining 80%.
Have a small list or don’t have time to do a test? Consider creating a semi-retina image that’s only 1.5 times the original size. That can be a solid compromise between image quality and load time.
4K ultra-high-DPI screens are already found in many TVs on the market, and Sony has introduced a few smartphones with 4K displays—all a part of their Xperia Premium line.
Keep an eye on Samsung and, in particular, Apple. The overall smartphone market won’t truly start to pivot to ultra-high-DPI screens until they introduce smartphones with 4K displays.
That said, even if Apple and Samsung put 4K displays in all of their new phones tomorrow, the trade-off in image clarity probably wouldn’t compensate for how much having 4K-optimized images would slow email load times. Given current network and WiFi speeds, 4K-optimized images in emails simply don’t make sense.
However, 5G networks are already available in some US cities and 5G smartphones are set to debut this year. The higher speeds promised by 5G may eliminate the load-time concerns with retina images, making high-DPI images the status quo for email.
At that point, we’ll need to start having serious conversations about when to use 4K-optimized images in emails. Thankfully, we’re at least a couple of years away from that being a legitimate concern.
Need help with your email creative? Oracle Marketing Cloud Consulting has more than 500 of the leading marketing minds ready to help you to achieve more with the leading marketing cloud, including a Creative Services team that can handle any aspect of email design, coding, testing, and copywriting.
Chad S. White is the Head of Research at Oracle Digital Experience Agency and the author of four editions of Email Marketing Rules and nearly 4,000 posts about digital and email marketing. A former journalist, he’s been featured in more than 100 publications, including The New York Times, The Wall Street Journal, and Advertising Age. Chad was named the ANA's 2018 Email Marketer Thought Leader of the Year. Follow him on LinkedIn, Twitter, and Mastodon.