A perfect frame is that which is composed of members just sufficient to keep it in equilibrium, when loaded, without any change in its shape. 
A perfect frame should satisfy the following expression: 
m = 2j − 3 
where m = Number of members, and j = Number of joints. 
An imperfect frame is one that does not satisfy the above equation (m = 2j − 3). 
If m < 2j − 3 then the frame is called a deficient frame. 
If m > 2j − 3 then the frame is redundant. 
Given: 
m = 5, 
j = 4 
∴ m = 2j − 3, 
5 = 2 × 4 − 3
5 = 5 
Hence, The given frame is perfect frame