Joe Hemsani Posted July 25, 2006 Share Posted July 25, 2006 Hello, I have a question about T-Stops. Why are there T-Stops in numbers such as T/1.7, T/1.9, T/1.3, T/2.1 if those numbers arent even thirds of a T-Stop. What does this mean?? Thank you! Link to comment Share on other sites More sharing options...
Premium Member Adam Frisch FSF Posted July 25, 2006 Premium Member Share Posted July 25, 2006 You will find that these stops are only there to describe the lowest setting and is a way for manufacturers to inform us about how fast their lens is at the widest aperture. Hence a T1.3 lens is slighly faster than the 'normal' setting of T1.4 and something they want to brag about. Link to comment Share on other sites More sharing options...
Premium Member Stephen Williams Posted July 26, 2006 Premium Member Share Posted July 26, 2006 . Hence a T1.3 lens is slighly faster than the 'normal' setting of T1.4 and something they want to brag about. Hi, That extra 1/3 stop can be useful at times! Stephen Link to comment Share on other sites More sharing options...
Joe Hemsani Posted August 2, 2006 Author Share Posted August 2, 2006 thanks I just wondered why thery did it but now I know!!!111 best regards Link to comment Share on other sites More sharing options...
Premium Member Chris Keth Posted August 2, 2006 Premium Member Share Posted August 2, 2006 A t-stop is just a ratio of the focal length to the iris opening. It doesn't have to be expressed in whole, half, or third stops. Link to comment Share on other sites More sharing options...
Premium Member Stephen Williams Posted August 2, 2006 Premium Member Share Posted August 2, 2006 A t-stop is just a ratio of the focal length to the iris opening. Hi, You are referring to F stops. T stops are corrected for light transmission. Stephen Link to comment Share on other sites More sharing options...
Matt Pacini Posted August 2, 2006 Share Posted August 2, 2006 So this begs the question; why aren't ALL lenses rated as T-stops? It's obviously the only accurate measurement, yet all still photo lenses are in F-stops. Why wouldn't the entire industry switch over? MP Link to comment Share on other sites More sharing options...
Premium Member Stephen Williams Posted August 3, 2006 Premium Member Share Posted August 3, 2006 So this begs the question; why aren't ALL lenses rated as T-stops?It's obviously the only accurate measurement, yet all still photo lenses are in F-stops. Why wouldn't the entire industry switch over? MP Hi, Most SLR still cameras have built in light meters so it does not matter what the F to T stop relationship is. For motion picture work lenses need to match both in color and exposure throughout the set. Stephen Link to comment Share on other sites More sharing options...
Premium Member John Pytlak RIP Posted August 3, 2006 Premium Member Share Posted August 3, 2006 A separate T-Stop calibration becomes more important with lenses that have significant light losses (e.g., complex zoom lenses with many elements, older lenses that had more internal light loss due to flare). A modern prime lens with multicoated elements is unlikely to have much more than a 1/3 stop difference between the f/stop and T-Stop calibration, which is well within the latitude of the film. Link to comment Share on other sites More sharing options...
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