Most excellent render.  Very nice.

The ants picture features DoF and Atmosphere Volume: focus_Distance 6.68; Depth Cue Start Dist 6, End Dist 24

The Depth Cue settings make the 'fog'.  The Atmosphere settings are found in the Material Room.  I changed the DepthCue_Color from  black to white and used the above start and end distances.  I'm not sure about Volume_Density, Stepsize and Noise, but I can check if you like ...

I used the same Python script I mentioned above to figure the focus_Distance.  I made certain I was 'looking through' the Main Camera, clicked on the leading ant's head, went to Window, Python Script, Render/IO, Calc DoF Focal Distance.  The script provided a factor to Copy and Paste into the Main Camera focus_Distance Parameter.

The script also provides a starting point for figuring where the Depth Cue should start and stop.  As I said above, I also raised the Pixel sampling AND lowered the Min Shading Rate to values higher and lower than anything I normally use.

Saving cameras shouldn't be a problem for you.  As above, use your Dots or save Cameras directly to the Library. 

The Ants file is on another computer, and I will have to look there to see what Density, Stepsize and Noise I used.  Also, having more that bit of trouble typing right now ....