The very first thing you need to do is to login into your Blogger Account, and from the list of your blogs select the one which you would like to disable the image lightbox. Go to Settings ›› Posts and comments ›› Showcase images with Lightbox and from the drop down change "Yes" to "No" (shown in the screenshot below.
We hope this quick tip may have helped you in learning how to disable image lightbox in blogger. Do let us know what are your thoughts about using lighbox in your site. Here at MyBloggerLab, we are not using lightbox and we have also remove hyperlinks from the images to avoid users to click on the images. Share your thoughts, in the comment below.