It’s about the soul. Vampires don’t cast reflections because they are soulless. Cameras have been criticized for stealing peoples souls. Ergo, a camera would suffer the same fate as the mirror: no soul to capture or reflect.

But I mean it’s just made up lore. That’s admittedly stretched thin.

In Daybreakers the vampire society uses cameras and monitors since they don't show up in mirrors.

Classically, mirrors used silver metal, and black and white photographs used silver halide. So strictly speaking, a digital or even color film camera would work.

I'm pretty sure those sensors use silver, which won't capture the vampire's image.

I asked ChatGPT and this is what it told me:

In traditional vampire lore, the inability for vampires to cast a reflection in mirrors is often attributed to the idea that they lack a soul. This concept has been widely popularized in literature, film, and other media.

Traditional film cameras use a mirror to reflect the image onto the film (in the case of SLRs), while digital SLRs use a mirror to reflect the image onto a digital sensor. If we follow the lore strictly, a vampire wouldn't appear in these photographs.Modern smartphone cameras, as you correctly pointed out, do not use mirrors; they use digital sensors to capture images directly. If the folklore's basis for invisibility in photos is strictly tied to the presence of mirrors, then theoretically, a vampire would appear in a smartphone photograph.

However, the interpretation of vampire lore varies. Some versions might suggest that it's not just mirrors that prevent their appearance but any form of reflection or reproduction. In that case, even smartphone cameras might fail to capture them.

Don't go to the house of mirrors exhibit in Transylvania.