Additionally, since the limiting resolution is usually defined as the point at which the MTF is three percent or less, this would also be the maximum resolution of the tube. The MTF is affected by every part of an image intensifier tube's operation and on a complete system is also affected by the quality of the optics involved. Factors that affect the MTF include transition through any fiber plate or glass, at the screen and the photocathode and also through the tube and the microchannel plate itself.