Here’s how much smaller the sun looks at aphelion
The sun at aphelion appears smaller in our sky, as shown in this composite image. This image consists of two photos, taken just days away from a perihelion (Earth’s closest point to the sun) in January, 2016, and an aphelion (Earth’s farthest point from the sun) in July, 2017. The gray rim around the sun (actually the perihelion photo) illustrates that, as seen in our sky, the sun is about 3.6 percent bigger at perihelion than aphelion. This difference is, of course, too small to detect with the eye.
Although taken 18 months apart, and a few days from the events due to adverse weather conditions, you can see there is an unmistakable size difference of the sun as viewed from Earth when it is closest at perihelion and furthest away at aphelion.
By the way, the moon changes its size in our sky, too, as it moves in its elliptical orbit around Earth. Read more: Close and far moons in 2018
Bottom line: Composite image showing the size of the sun at perihelion and aphelion.