UHD web guidelines state that photos and graphics that are to be place on UHD web pages should not contain text. What this means is, do not rely on an image, a photograph or a logo to convey your content. This is to comply with the Americans with Disabilities Act (ADA) requirement for images for the web. Relying on a graphic image (jpg, png, pdf) to convey the content means people using screen readers cannot access the content.
ALT tags in the HTML code does help to describe an image. However, there is a limit to the characters that can be used inside the 'alt' tag. If it takes too many characters in the 'alt tag' to fully describe the image, Google search begins to ignore the page, which is detrimental to search results. This is another reason why using images to convey content is discouraged.
It is acceptable if your photograph has text that was captured as part of the image, do not just create a graphic of text to serve as the content to be placed on a webpage (or social media or in an email).
Additional information about photography and images can be found in
UHD Web Style Guide. This guide contains 'Do's and 'Don'ts' for lighting, cropping, color, image quality, icons, QR codes and image size and resolution. Additional guidelines for images are listed on UHD's Web Image Guideline page.
These guidelines are still in effect for 2020-21.