I need a really simple, fool-proof method to obtain this effect: I want to leave the letterbox colored while make all the surrounding area in a deep dim gray shade, the grade of gray that I see is like the one in the other picture.
Please consider that I'm pretty new in Photoshop and graphic design in general. I tried using paths to delimit the zone but the result was terrible and not sharp.
I would start by selecting the Polygonal Lasso Tool and then outlining the mailbox. Ideally, you would use the Pen Tool for more precise results, but you wanted simple/quick
Then, create a Hue/Saturation Adjustment Layer. Select it from the options, by clicking this icon at the bottom of your Layers Palette:
You will now need to invert your Layer Mask. Do so, by clicking on it, in your Layers Palette to bring up this menu:
After it's inverted, click just to the left of that little chain link icon, to bring up the options for your Hue/Saturation Adjustment Layer and bring the saturation all the way down
As you may see in the image above, I also decided to decrease the contrast a bit, to make the grays more uniform
Create a Brightness/Contrast Adjustment Layer the same way you made the previous one. You can then drag your mask from the first layer to your second, holding down Alt to copy it. Adjust the parameters to your liking
