Aperture setting combined with faster glass

Started 5 months ago | Questions thread
MitchAlsup Veteran Member • Posts: 4,963
Re: Aperture setting combined with faster glass

danferrin wrote:

The simple answer is no.

The real answer is almost always no.

F 4.5 is f 4.5. Regardless of the lens, if your camera is set to the same iso and aperture, the shutter speed will remain the same. The advantages the f 2.8 version of the lens might have over the f 4 version at f 4.5, might be in sharpness, distortion, etc., though I haven't looked at any test charts to see if that is the case.

The only difference between the 16-35 F/4 and F/2.8 is the amount of glass between light entering the lens and alight arriving at the sensor. In cinema it is known as T-stop to compensate for slight differences in glass thicknesses and lens transmission values.

F/4.5 tells you the geometry of focus (i.e., amount of blur per distance from focus.)

T/4.5 tells you how much light arrives at the sensor.

In modern lenses, T-stop and F-stop are very closely related with T-stops only being a few decimal digits different than F-stop. In camera metering will compensate for variations between F-stop and T-stop.

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