I have a photo of a person (blurred for privacy) and I used the adjustment brush on the eyes to experiment a bit. While switching the adjustment brush on and off I noticed that not only the eyes changed, but the background was noisier when the adjustment brush was on.
I then did a test with the images shown below.
The left most image (
image1) is a JPEG export of the RAW with the adjustment brush turned off, the middle image (
image2) is the same image exported to JPEG with the adjustment brush turned on and the right image is the result of placing
image1 in Photoshop and setting the blending mode to
My expectation would be that only the eyes would show a difference (and they do, there are two black spots where the eyes have been adjusted). However, the backgrounds shows a lot of difference as well. This is unexpected.
Could someone explain to me why this is happening?