Sigma Art transmission values

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Eliot Kramer Contributing Member • Posts: 756
Sigma Art transmission values

Hi,

Anyone has guidance/reliable information/education regarding transmission values in general and specifically the Art line.

I am looking at Sigma 50mm and 85mm Art and some sites list the transmission value at 1.7, others at 1.9.

Although the differences are minor, they do mean something. Assuming things like bokeh are not important to me, the this is going to impact the choice of lenses it can be compared to, such as F1.8 and 2.0 options.

For example, if the Sigma T is 1.9 and another F1.8 lens is 2.0 then other considerations start coming into play that are more important (again, assuming one is not specifically after the 1.4 DoF).

Anyone has looked into this?

Although I have done some crude testing myself by just keeping all parameters equal and swapping out lenses it seems the lens communicates to the camera and that results in some additional alterations that the camera applies that I can't seem to pick up on.

Lastly, does anyone know this? Does the T value include vignetting?

So for two lenses with equal aperture and all other settings being equal but with different vignetting, is the T a total measure of all light transmitted, and therefore, the lens with less vignetting has higher T, or is it the maximal brightness obtained in the center and therefore the lens with the brightest possible value has the higher T.

Thank you.

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