When we buy lenses, we look at how much light a lens can receive. For instance, when we look at pro level lenses that have an aperture value advertised at f /1.4 or f /2.8, you might say say "Wow! This lens is GREAT for low light!" because it can bring in a lot of light into your camera's sensor. You may think to yourself... am I REALLY getting whats advertised?
Yes and no lol. Here's why...
Almost all lens manufacturer's advertise their lenses in F-Stop numbers. Depending on the amount of transmission of light a lens can receive, one f /2.8 lens can actually have a light transmission value of T3.0, meaning the picture will be darker than other f /2.8 lenses. Why is that? F-Stop (Focal Length or Aperture) measures what will be in-focus, whether its only the center or the whole frame. Meanwhile T-Stop (Transmission) measures the amount of light the lens can receive. So are F-Stop and T-Stop the same? No.
T-Stop measurements is a term used in Cinematography. Cinematographers care more about the amount of light that can be transmitted through the lens. As a still photographer, it helps us know if our lens is actually good for low light photography.
To get the T-Stop measurements of your lens, you can head on over to DxOmark.com, search for your desired lens and look at the "Transmission" column to find out.
Drop a comment below and let us know what you think.