The original image is a JPG file with:

Resolution: 240 px per inch

File size: 1.5MB

Dimensions: 5356×3571

Compressed to a PNG:

Resolution: 72 px per inch

File size: 15.6MB

Dimensions: 5356×3571

Compressed to a GIF:

Resolution: 72 px per inch

File size: 11.5MB

Dimensions: 5356×3571

 

Observations:

Straight away the first observation I made was that the smallest file was JPG even when it held the most pixels per inch 242. But the second biggest file was PNG  holding 72 pixels per inch. This is the same as the GIF resolution but as you can see from above the the GIF file size is the smaller then the PNG. Throughout all the changes the file dimensions never change. Overall you can see that the JPG looks the best having the best resolution and is the smallest size. This is because JPG is a vector consisting of only 1 layer.