I often talk about using high resolution images when creating accessible assignments, but have never formally explained what that means, or how they can be created. Today, I will be sharing what I have learned about high resolution images, why they are important, and how to create them. I’ve gathered this information from personal experience, talking to friends in graphic design and art related fields, and from taking graphic design and multimedia courses at my university. I link to related posts on my blog as well as posts from trusted outside sources.
What is a high resolution image?
A high resolution image is defined as having 300 dpi (dots per inch), which is the minimum image resolution for many publications. Low resolution images are considered to have around 72 dpi, which is fine for web use but not so great for print. High resolution images can be enlarged easily without any pixelation or appearing blurry to the eye. High resolution images can also be scaled to different sizes for print or web use.
Common image formats
The most common image formats I have seen for accessible assignments include JPEG, PNG, and GIF. I prefer to use PNG whenever possible because it is great at displaying images with large amounts of uniform color, which is common for assignments, especially in math and science classes. JPEG images are also great though, because they have a smaller file size, but can gradually become lower in quality when edited and saved over time. I tend to shy away from GIF files since they have lower color resolution and are often moving images (though not all are) and I am sensitive to movement and flashing lights.
Why is it important for low vision students?
High resolution images are important for low vision students for many reasons. First, they need to be able to zoom in on images and magnify details as necessary without the image rendering as blurry. Second, the images need to be accessible for different types of devices, including computers, phones, tablets, and in print. Lastly, images need to be scaled for everything from projectors to assignments on paper.
Color vs black and white
Some people believe that black and white images are the most accessible, but that is not the case. Images with color can still be accessible for low vision users, especially those with rich, clear colors. If needed, color can always be added to make parts of an image easier to see- I talk about this in my post on making music accessible here.
It’s important to remember contrast and readability when choosing colors and color schemes for images. Avoid images with very light colors or pencil that may look washed out. Dark backgrounds with light colored features, or light colored backgrounds with dark features are best. Some examples of high contrast color schemes include canary yellow and black (read more about canary yellow on Paths to Literacy here), lime green and black, white and black, canary yellow and cobalt blue, and cherry red and black. Read more about colored backgrounds and the readability of text here.
Searching for images
To find images that are high resolution on Google Images, use search tools to request images that are large in size, or larger than specified dimensions. I recommend showing image sizes when going through images to determine which image sizes are best for your needs. Other image sources with high resolution images include Wikimedia Commons, US government websites, university image libraries, and similar.
Creating images digitally
There are many tools to create high resolution images digitally. On Windows 10, the paint application has many different options for drawing images using a stylus, mouse, or finger, as well as the ability to draw large lines. Users can also save PowerPoint slides as images and add shapes, text, and anything else to the slide to create an accessible image- read more about creating accessible PowerPoints here.
Another great app on the iPad, iPhone, and Android is PicsArt, which allows users to draw on images, create their own images, and increase the size of images. One downside is this app has ads, but this can be solved by using the app in airplane mode or with data turned off. Read more about PicsArt in my list of apps that help students with low vision in the classroom here.
Creating images by hand
When creating accessible images by hand, use high-contrast writing tools such as Sharpie pens and markers. I recommend using cardstock or other thick paper so the colors show up well. Utilize rulers, protractors, and compasses to create uniform shapes and object sizes whenever possible. Alternatively, accessible images can also be created using tactile materials- read more about creating tactile images here.
When scanning images into the computer, opt for the highest resolution available. Make sure the image is clean and wrinkle free, with no artifacting or wrinkles in the paper. Images can also be scanned in using the Microsoft Office Lens app- learn more about it here.
Reverse image search for a higher quality image
If you have a pre-existing image that is low resolution, you can use Google’s reverse image search tool to find the image in different sizes and formats. This does not work for all images, but it’s great to check first and see what you can find. To use reverse image search, visit this link here and upload your photo.
Don’t forget alt text
When creating images to be used in web layouts or other assignments, don’t forget to add alt text. Alt text is read by search engines and screen readers so that way users can figure out what’s in an image. It’s usually a one or two sentence description of text and general image appearance. Do not use the file name as alt text, as this information is not helpful. Read more about alt text in my post on creating accessible Microsoft Word documents here.
Finding and creating high resolution and accessible images is important for creating accessible assignments and supporting students with low vision. With these tips, students, parents, teachers, special education staff, and teachers of the visually impaired can learn more about high resolution images and why they are important.