Jtdcftul

Below are real photographs, I was present when they were shot. The photographs were taken between 12:00 to 14:00 on a slightly overcast day. The photographer may have taken many frames.

What postprocessing was likely done, such that the people stand out in the photographs?

I'd guess it's as simple as selecting the subject in Photoshop - with a tad more care & attention than I've used below, then leeching out the saturation in the background & tonally balancing towards a sepia effect.

As a very quick demo I did the same thing but made it a pretty garish purple instead.

Once you have your mask you can treat inside & outside of it in totally different ways.

The subjects have been left with realistic colouration, which I think is what is providing the majority of the visual separation - that & the physical separation from the ground, which pushes them into the unsharp area of the background. Note how the effect is less emphatic on the small boy, especially lower, where he's connected to the equally sharp ground at that distance.

I don't think the focus has been played with. I think it was shot on a wide enough aperture that the background is blurred by simple distance. The ground underneath them is still reasonably sharp.

I also don't think it would be compulsory to be using flash, so long as enough light was getting in, or set to a high-enough ISO, to use a short exposure.

The light on the people & the trees seems to match - little to no shadow at all, which matches the OP's description & the almost 'white-out' cloud cover in the back of the shot.

Didn't the photographer use flash?

A common practice to make subjects "stand out" is to use flash for proper subject exposure, and to use camera settings to slightly underexposure the background. That is my guess here, instead of post processing.

There area few ways of making such photographs. You could, for instance, use a large aperture to create a shallow depth of field whereby you blur out the background. The human eye doesn't like to look at things that out of focus. By creating a shallow DOF, you will put visual emphasis on your subject.

Another way is by creating contrast between your subject and the background. One way to do this is by having your subject brighter than the background. You could use fill flash or simply place your subject in a scene where they have more light falling onto them than the background.

Combining these two methods would be even better.

What the photographer has done with the images that you've posted is to create a composite. The images are apparently a combination of a background and the people were placed over it. The photographer either took the background image out of focus, or used a blur filter (i.e. Gaussian blur)..