I was recently browsing photos of early Apollo missions and noticed that the plume of the Apollo 4 during launch is significantly bigger than that of Apollo 8. Wondering why is that? 

[![Apollo 8 and 4 plumes during launch][1]][1]


I am not a hoaxer or something like that. I know for sure that people from the planet Earth walked on the Moon six times. The evidence to support that is overwhelming. Just really curious why such a difference. Does it depend on payload mass or different engine modes or something like that?

Photograph sources: 
[Apollo 4](https://www.hq.nasa.gov/office/pao/History/alsj/a410/ap4-67-HC-745HR.jpg) and [Apollo 8](https://www.hq.nasa.gov/office/pao/History/alsj/a410/ap8-KSC-68PC-315.jpg)

  [1]: https://i.sstatic.net/CXJAJ.png