Shadow catcher. Why am i getting different shadow density Top image is a shadow catcher turned on with transparent film laying on the #404040 background (default in cycles render). I made this inside a photoshop.
While the bottom image is the shadow catcher turned on without transparent film. 

As you can see the shadows are denser on the top image (transparent). Why is that, and is it possible to fix?
This may be a color management issue. For physically correct results, compositing should be done in a linear color space, like Cycles and the Blender compositor. If you save the image as e.g. a PNG file and then do compositing in Photoshop the result is likely to be wrong.

For external applications you can save images as linear OpenEXR, and/or try to tweak Photoshop settings to work in linear color space.