Caption with Cotent-fill: Contain

Site URL: https://talusandolsek.com/work/outdoors-t2cgl

I was able to add captions to my gallery in light box following another forum, but I want the captions to be aligned to the left of the image. My issue is that the images use Content-fill: contain so the image is dynamically resized so I don't know how to align the caption with the end of the photo and not the padding on the side. Any help with would be appreciated!