"Correct" way to add texture for a photo print in a scene. Fix "over-exposure" Total beginner to Blender here, so please pardon my general ignorance.

I'm trying to render product shots of some photographic prints for my wife. I've bought an interior scene from evermotion which already had some prints on the wall, and am trying to substitute her photos for those prints.

To do this, I've deleted the meshes for the existing prints (they were using a texture atlas for all of the prints, which seemed like unnecessary additional complexity for now), added in planes for the new prints, and used a simple "image texture" material on them. This approximately works, but the photos look over exposed when I render -- this is the problem I'm trying to solve.

Moreover, I'm a bit confused about what's actually happening: she sent me JPEGs of developed RAW files which had already had exposure, tone-mapping, gamma, etc applied in Lightroom. My understanding of 3D graphics was that you generally wanted to work on linear data and then apply the tone-map and gamma to the final render. So I guess I'm not surprised that it's come out wrong, but I'm at a bit of a loss to understand the best path to making it "right".

Would appreciate any pointers on this! Thanks!
Ok, here's what I ended up doing. Thank you @virgil-sisoe for the pointers.

First up, I may have been overly concerned about gamma correction: it looks like Blender automatically gamma "uncorrects" (wrongs?) texture data when it's loaded, so the output of the texture node can be assumed to be linear.

From there I added a "Separate RGB" node, and added a Multiply node on each of its 3 outputs, followed by a "Combine RGB" node. I set each of the multiply nodes to 0.5, so -1 stop.

(arguably it should have been -1.6 stops, but -1 looked right given the brightness of the rest of the scene).

I added gamma nodes to the input and output, but have the input gamma set to 1 (so no gamma adjustment), and the output a little over 1 to add just a touch of contrast.

The last thing I did was to switch from the principled BSDF shader to the diffuse BSDF shader. I figured that I only want diffuse here, and I don't yet fully understand the principled shader.

This looks ok, and I think it will suffice for my current purposes.

Here's what I ended up with: