[garyctang]

Take a photo of white wall, use ACDsee to crop and rotate the original file. then compare the size of the files.

1. Original photo Jpeg file size ~3M
2. Rotate the original photo a little bit and then crop it, file size reduce to ~900K.
3. Crop 1/2 area of the original photo, file size reduced to ~ 500K
4. Crop 1/2 area again after step 3. file size = 250K

Can someone explain WHY the size of the photos reduced so much after some basic post process?
Does it mean lots of information has been lost in the process?
Why the file size change a lot in step 2 and 3 but not much change in step 4?

THANKS.

[peterhtchan2000]

When you use ACDSee to save JPG, it would use default compression and quality ratio. You can use no compression to have full size photo.