This post is intended merely to illustrate the "floating" issue mentioned previously. Image #1 is a downscaled JPG of one of the source NEF (Nikon's RAW) images in #2. I also adjusted the brightness to make it a bit easier to see under the Jeep. Mostly what this image tells me is that I cannot hold the camera level.
You can see that the shadow under the Jeep in #1 is there and everything looks normal. In #2 there are no shadows and the Jeeps appear to be floating above the street. (Please ignore the rough masking around the tires.) The problem is that were I to include the shadows in each Jeep's layer, they would cover part of the Jeep in the layer beneath it.
The only way I can figure out to include the shadows is to make each Jeep's shadows into their own layer and place that layer behind all the Jeep layers and in front of the background. On this image there are few enough Jeeps that it is feasible, but some of these constructions have 20-30 source images resulting in 40-60 layers, and adding shadow layers would result in a total of 60-90 layers. Now we're talking about a whole lot of work that I am too lazy to do.
I suppose someone has made a tool to digitally generate these shadows, but if they did I haven't found it.
Would using an Exposure Layer in the semi-final photo work....rather than each individual photograph?
In you photo it is obvious the Jeep is heading down hill, the building contractors never hear of a Plumb line, and those are a special variety of trees that grow similar to Acer circinatum commonly referred to as Vine Maple.
Ah Andrew, the only way I know of achieving your goal would be to add a mask for each layer and mask in/ot detail as desired.For example, where the shadow overlaps the Jeep on another layer you would have to mask out the shadow.
You could also try changing the blend mode on the layers, but as both Jeep and shadow are dark I don't think this will work.
Hope this helps, you say you have 20-30 source images but there seems to be only 3 or 4 that would need this adjustment.
I'm interested to see what solution you come up with.
I did a Google search and lo, there is a drop-shadow tool in Photoshop that I did not know about. I played with it a bit and it did not really seem to work well for this image, but it's nice to know it exists and may come in handy later.
Perhaps more relevant, Unmesh posted about creating shadows on Piximperfect several months ago, I haven't had time to fool with his technique, but it looks really promising.
https://fb.watch/iRfV_pqWzz/
Yay! That's good news. Look forward to see what you figure out with it.