The sensitivity of a detection reagent has to be chosen depending on the target protein level in the endogenous sample. 

For proteins of high and medium expression, using ECL with mid picogram detection range, like AgriseraECL Bright, is going to result in a clean blot, with low or no background. 

For proteins of low expression, a more sensitive ECL has to be used, like
AgriseraECL SuperBright, with extreme low femtogram detection range. Please note that when using more sensitive ECL, blocking reagents also have to be used in higher concentrations. 

In the example to the right: 
PsbA is a photosynthetic protein of high abundancy, therefore using high protein load/well and highly sensitive detection reagent will contribute to increased background signal. The conditions can be optimized by using a lower protein load/well as well as a less sensitive ECL reagent, like in this case AgriseraECL Bright with mid picogram detection range. Read more about Agrisera ECL Reagents here.
 Agrisera Chemiluminescent Detection Reagents
 Technical blog

Technical blog