It’s time to represent now inside the first ellipse another one, setting the layer’s adjustments: Fill 0%.



Select for it Blending Options>Gradient Overlay:

 

 



Represent one smaller ellipse, as it is pictured below:



Select for it Blending Options>Gradient Overlay:

 

 



Blending Options>Stroke:

 



The button is finished. It’s necessary now to represent the camera’s flash effect. Take the Rounded Rectangle Tool (U) and the color #A8AAB to picture the basic element for our flash effect.