How to control image transparency like photoshop Im my model in the soup there is curry leaf. And i want to make that leaf transparent like photoshop. As if leaf is dip and floating in the soup. How to control the image. Any suggestion or help. Thanks
you can add another "mixshader", connect the output of the current "mixshader" to the new. 

Afterwards you can connect the "transparent shader" to the top of the new "mixshader".

The factor can be a "color ramp" that is dependent on Z of the object (in fact you can use whatever factor here to control another transparency).

Check the printscreen of the proposed node setup: