This is kinda a technique I just made up on the fly looking at your images, but this is what I did and just really relates to grainy images.
1. from filters, "select convert to smart filter" (This allows you to adjust filters after you have applied them )
2. from filters go to "noise" then "reduce noise" you can do this a few times if you want to get a smooth image, don't worry too much about losing detail (you will notice that it adds the filters now as layers due to the smart filter you added).
3. Ok so now we get the detail back, go to the layers panel and turn off the eye symbol next to smart filters to revert your image back to the original, then go to the channels tab next to layers and turn off all but one of the colours, you want the colour with the most contrast to be the only one visible, the image will now look black and white.
4. cmd+click on mac or ctrl+click on pc on the remaining cannel, and you will see that is makes a selection of the darker areas.
5. turn on all the channels again and go back to the layers panel, turn on the smart filter again.
6. you will see in the layers panel a layer called smart filter that has a white box next to it, this is a mask and depending on its colour can act as a block or mask against the denoise filter you added. ALT click on this white box and the screen should turn white, then press making sure your background colour is set to black press ctrl+backspace to fill the selected area with black. you can do this more than once if you wish to, the more you do it the less the de-noiser will affect the blackened area. Alt+click on the layer to get back to the original image.
7. Voila, thats all I did... P.S. creating new adjustment layers from the bottom of the layers panel is always the best option for editing basic properties, always try and work in a non destructive way as in you can alway turn on and off or turn up and down the opacity of your filters or adjustment layers. when making a selection if you press the "Q" button you can toggle quick mask allowing you to paint with black and white brushes, a selection, this is useful, for using a soft brush, creating blended selections.