Question: what is the difference between first focal plane and second focal plane?
Answer: A riflescope's reticle is placed in either the first focal plane (FFP) or the second focal plane (SFP). The main difference between them is that an SFP reticle will appear to be the same size regardless of magnification. ... One advantage is that you have a strong and easy-to-see reticle even at the lowest magnification.