We recently created an image service from a mosaic dataset of our 2017 ortho images. We have cached it at all scales (125,000 to 125). At the 125,000 scale there are 4 tiles at a size of 0.15 MB. At the 125 scale there are 1,924,852 tiles as a size of 51.96 GB. We also have has an image service created the same way of our 2015 orthos, however the file size of the 125 scale is only 8.26 GB. the 2017 source images are jpegs, whereas the 2015 source images are ECW, but the file sizes and numbers of the source images are almost identical between the years.
NOTE: 2015 tile format is JPEG (96 DPI) and 2017 tile format are PNG24 (96 DPI)
We are trying to figure out why the 2017 ortho image service is so large compared to the 2015's, and how we can make it smaller. Please let me know if there is any other information required to diagnose this!