I am looking for to 'grey out' my image entirely - the main purpose is to be able to have high detailed picture and still allow me to read clearly written contents at the top of the image. The grey out filter/effect I am looking for looks like some web or app components background when a pop-up comes out. I am attaching an image showing you an example. I am a Photoshop user but can use something else if necessary. I have tried many filters but none has this disabled/grey mask effect.
Duplicate the layer going to the menu bar and choosing Layer -> Duplicate Layer.
Go to the menu bar and choose Filter -> Blur -> Gaussian Blur and apply a small setting like 2 to 3 pixels. This will make the text appear to be shown in a shallow depth of field. This step is optional but I find it helps to sell the illusion.
Create an adjustment layer by going into the menu and choosing Layer -> New Adjustment Layer -> Hue/Saturation...
With the adjustment layer selected, adjust the 'saturation' property to something low like -40 or -50. This really depends on how bright and colorful your picture is to start.
You may want to adjust the brightness property as well to achieve the desired effect. In this case, I went with -30.
That should be everything you need. There aren't any filters that come with Photoshop to achieve the results here but this process takes less than five minutes and is easily customized based on the desired effect.