t stop

A T-Stop is the actual measurement of light transmitted through the lens. So, a 100mm lens at f/4 has an aperture opening of 25mm. That same 100mm lens at f/2 has an aperture opening of 50mm. Twice the diameter means four times as much area, so, two stops more light gets in. The focal length and aperture relationship allows a certain overall ... this house don t feel like home