Nige's suggestion is the best way forward, and will likely be a solution, but you might also want to run the following macro once (in the link below) in order to find the correct scaling value for your image requirements. Knowing the value from this macro would likely give you a different way to solve the problem, because all you would have to do is re-scale the image to the correct DPI value before using it in a Find Image task. Something like this:
I think you can redefine that shortcut in System Settings.
