Problem using the rectangle tool in Image J

So in image 2 when I measure band B and band C together using the rectangle tool, band C, the lighter band, is normalized to that of Band B or the darkest band that is measured. This causes the absolute intensity values that I get to become skewed. I want to measure bands among different images. In Image 1, band A should certainly produce a much smaller intensity value than band C, just looking at the two pictures visually. However, since band C is normalized to band B, band C produces a smaller intensity value than band A. Is there a way to fix this or is it just that Image J works this way. Any help greatly appreciated.

2 posts were merged into an existing topic: Trouble Using the Rectangle tool to measure Western Blots