NS 958 east of The Plains, Virginia, June 4, 2016; photo by George W. Hamlin
Yes, you have a First Amendment right to self-expression, which includes photography; however, that doesn’t justify being oblivious to others as you do so.
You certainly were aware of our existence and location, since you passed and spoke with us on the way to do your photography …after the vehicle you were in passed the signs indicating that this was private property, without obtaining permission to be there.
Most photographers consider it courteous, when arriving at a location where other photographers are present, to stay out of the way of each other’s shots. Generally, this means that the first arrivals essentially set the location of a photo line, and those coming later either stand with them, or find another, non-interfering location.
The other two people in your party complied, quickly, when advised that they were blocking our shot; why didn’t you? You seemed reasonably ambulatory when you walked up the road; couldn’t you have moved with them?
Selfie-shooters and others: have fun, enjoy what you’re doing, but first, do no harm, especially to people engaging in the same general activity (photography) that you are. You don’t want to be photo-bombed; do your best not to do unto others as you would not like to have done to you.