For Blade Runner 2049 movie I saw on YouTube that they made a miniature scale city, but in some shots you can see the life sized actors and the city in the same shot.
I am wondering how are they able to combine these to elements of different scale to make them look like they are the same size?
By compositing
Compositing is the combining of visual elements from separate sources into single images, often to create the illusion that all those elements are parts of the same scene. Live-action shooting for compositing is variously called "chroma key", "blue screen", "green screen" and other names. Today, most, though not all, compositing is achieved through digital image manipulation. Pre-digital compositing techniques, however, go back as far as the trick films of Georges Méliès in the late 19th century, and some are still in use.
This effect is called Miniature effect
A miniature effect is a special effect created for motion pictures and television programs using scale models. Scale models are often combined with high speed photography or matte shots to make gravitational and other effects appear convincing to the viewer.
This technique is still used but largely replaced by CGI.
There is a nice article form vashivisuals.com about it :
Visual Effects – Low Budget Filmmaking Miniatures and Forced Perspective
This article teaches how to achieve this effect without CGI.
But remember some films do use mix of CGI and Miniature effect to get their goal. Below is the behind the scene video for Blade Runner 2049 :
