You can specify alt text for each product photo on Shopify, but this method displays it as the image caption on the product detail page of the theme "Dawn". This will help visitors understand the product better, while also having an SEO effect. (There is no problem with using both the alt text and caption of an image from an SEO perspective.)
How to display the alt text set for an image as a caption on the product detail page of the theme "Dawn"
[Settings Step 1] Add the scheme to "main-product.liquid" and the label to "ja.schema.json"
[Settings Step 2] Modify "product-media-gallery.liquid"
[Settings Step 3] Add alt text to product images as needed
