The Influences of other Renaissance Artists
Raphael was the son of Giovanni Santi, a well-connected painter in Urbino. This allowed him to start a career at sixteen with many connections to the artists and patrons of Renaissance Italy. He learned from the styles and practices of these artists, who were some of the most significant artists in history.
Design elements in both The Agony in the Garden and the greater Colonna Altarpiece reveal some of the influences of Leonardo da Vinci.
Da Vinci's focus on creating three-dimensional space and figures is evident in the Colonna Altarpiece. Raphael overlapped the figures of the male and female saints and shaded the faces of the saints to create light and shadows adding to the three-dimensional effect. Raphael used softer painting around the faces of the female saints and used shadows and more definite lines around the male faces to give them the three-dimensional look that they have.
Raphael also made use of one-point perspective, with the throne the Madonna and Jesus are sitting on going backwards into the three-dimensional space.
Similarly, in The Agony in the Garden, Raphael overlapped the figures of the disciples with each other, Jesus, and other environmental elements, placing them in three-dimensional space. He also shaded their clothing and put dark shadows on the disciples, giving the figures their own three-dimensional shape.
Similarly, Raphael's placement and the way he emphasizes figures bears a lot of resemblance to the style of Perugino, whose workshop Raphael originally worked in prior to moving to Florence.
The female figures in the background of the larger Colonna Altarpiece are painted with softer strokes and are less well-defined than the male saint figures in front of them. These male saints have dark shadows and lines on their face which gives them definition and makes them appear more important.
This design style is also present in The Agony in the Garden, as the whole painting is painted with soft brush strokes aside from the most important figure in the painting: Jesus. Jesus' face is painted with hard lines which give it more emphasis as the most well-defined feature of the painting.
Robert Williams notes that this is how Perugino used his composition style, using lines and shading on figures placed in an image to emphasize the most important figures.
References
"Raphael." Benezit Dictionary of Artists. Oxford University Press, 2012, https://doi.org/10.1093/benz/9780199773787.article.B00148927.
Williams, Robert. Raphael and the Redefinition of Art in Renaissance Italy. Cambridge University Press, 2017.