The brush will help us to introduce several flares as it is pictured below and the object glass is almost finished.



Try to represent the roundness as the picture indicates it:



Now we should choose the Rounded Rectangle Tool (U) and press Alt button to represent a rectangle coming from the central part of the roundness:



Try to make a shadow, using the Blending Options>Drop Shadow and the objective glass is finished!

 

Start representing the button on our photo camera. It’s necessary to select the Ellipse Tool (U) and draw an ellipse as the picture demonstrates it:



Apply Blending Options>Gradient Overlay:

 

 



Give it volume effect with Blending Options>Stroke: