Most filmmakers and photographers are familiar with what an f-stop is and how each measurement on your camera affects your images, but how many know about t-stops? Sareesh Sudhakaran of wolfcrow puts it all in terms anyone can understand in the video below, explaining the differences between the two, as well as why it might be more helpful to use t-stops for filmmaking.
F-stops and t-stops both represent a certain value, one that is determined by the focal length of a lens divided by the diameter of the aperture. However, while f-stops are a "theoretical" measurement, t-stops are actual measurements that are tested when the lens is calibrated. This is why lenses that show t-stops tend to be so expensive, like the cinema lenses of Cooke, Zeiss, Angenieux, and Leica, because manufacturers have to put each lens through a lengthy and costly testing process.
So, what's the big deal? "My lenses have f-stops—should I find ones with t-stops? Are my images suffering because of this?" Hold your horses—and no, probably. Chances are you will be able to do your job just fine without the added power of an expertly calibrated lens with t-stops, but Sudhakaran shares three things you should think about now that you know more about f/t-stops.
- For lenses with f-stops, use scopes or the camera meter.
- If using light meters, stick to either f-stops or t-stops.
- T-stops only make sense financially if the time saved makes up for it.
You'll probably find this information on t-stops more useful when you get a job on a big budget feature film or commercial that shoots with lenses that use them, but until then, you can probably just put this in the "trivia" compartment in your brain.