I frequently use SHIFT + COMMAND + 5 to invoke screenshots … usually to Clipboard, but also to Preview, Downloads, or into an Email. (depends on the purpose).
Usually I am happy to get the screenshot without any Shadow.
But sometimes I desire to have a screenshot/s with a Shadow.
An example of when I would desire this option is if I was putting two or more screenshots into an email and because the images are “inline” in the body of the email, I’d like to show a differentiation between adjacent screen shots.
Using SHIFT + COMMAND + 4 + SPACEBAR gives a shadow, but it is the full Window. I want to be able to just do a section of part of the screen (using SHIFT + COMMAND + 5) but with a shadow.
Is it possible?
As far as I know, the built-in macOS screenshot utility doesn’t support drop shadows on arbitrary selections. You would need to edit a screenshot in an image editing program like Affinity, Photoshop, or SnagIt to add a drop shadow, tweaking the parameters to get a look that you like.
You could see if any of the options in the screencapture function in Terminal do what you’re looking for.
For example, screencapture -i -o will allow you to take a screen shot after selecting a region of the screen but—note I haven’t tested this—won’t “capture the shadow of the window”.
If you want to see a list of screencapture options, enter man screencapture into Terminal.
I have no first-hand experience to say that this still works in Tahoe, but I remember using it back in the day.
In a shell
defaults write com.apple.screencapture disable-shadow -bool true
And the relaunch the GUI server with
killall SystemUIServer
@josehill After testing the suggestions from @Halfsmoke and @Simon I agree with your comment that MacOS Screenshot does not support drop shadows on arbitrary selections.
I was able to turn off (or on) the drop shadow of Windows when invoking the ⌘ + SHIFT + 4 + Spacebar via the terminal command posted by Simon.
The man screencapture in Terminal had nothing to offer apart from…
-o In window capture mode, do not capture the shadow of the window.
Thank you everyone for your comments & suggestions. I’ll accept it’s not possible, and move onto more important things. 
Thanks for following up with your findings.
You might consider sending feedback to Apple requesting a shadow feature for arbitrary screenshots. If you do, I suggest specifically mentioning the Screenshots app by name, e.g., Screenshots.app.
Good luck!
I believe the shadows that are included with screenshots of windows or menus (shift-cmd-4 + spacebar) are there because they are the shadows “cast” by those UI objects. It’s not the screenshot process that adds them; they are generated by Aqua/Quartz/WindowServer and the screenshot process merely captures them as part of the window they’re attached to.
Arbitrary selection regions don’t have shadows of their own (though they may include shadows cast by objects in or adjacent to them. Adding them would require the screenshot service to add some graphics magic it doesn’t currently do. (I’m sure it could be done, but it would be, I think, very different from what it currently does.)
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That explanation makes sense Re the Aqua/Quartz/SystemUIServer and shadows.
On the premise of “if you don’t ask you don’t get”, I’ve submitted a feature request to Apple 
Kind of an aside maybe.
Press Command + Option + 4, hover over the desired window, then hold Option while clicking.
Holding Option during the final click removes the drop shadow.
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From an earlier Tidbits discussion:
Discussion here
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Just another vote for Snagit™. Terminal (semi-permanently) or some complicated key-combo is fine, if you can remember all the keys. Snagit can do drop shadows when/if you want it as well as several added adjustments:
(captured a capture the old fashioned way!
)Of course, you may not feel it is worth the price! ~$31/year.
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