Teodorian
Aktiv medlem
Som vanligt finns motstridande resultat:
http://www.btobey.com/nikon/nikon-70-200mm-f4-review.php
"T-STOPS
A t-stop is a measurement of light transmission through the lens. It represents an actual real value instead of an f-stop which is just a specification, focal length / diameter. T-stops are important for determining light sensitivity and typically marked lower than f-stops due to the impedance of light as it traverses through glass.
The 70-200mm f/4 exhibits a bit worse light transmission than the f/2.8 VR II. I could not measure it, but it is a small fraction of an f-stop less light than the 2.8 version provides. When shooting in low light, the 2.8 provides a smidge more light capturing capability."
Om skillnaden i transmission mellan 85/1.4G och 1.8G:
http://blog.mingthein.com/?s=Nikon+85/1.8G
"Perhaps the least obvious, and most surprising side effect is a huge reduction in transmission (read my article on the difference between T stops and f stops for more detail). At any of the wide apertures, the 85/1.8 G transmits between 1/2 and 2/3 stop less light than the 85/1.4 G; this is to say that if both are set to a physical aperture f2, then you’ll find the 85/1.8 G’s required shutter speed for a given exposure to be noticeably lower than the 85/1.4 G. In other words, if you set 1/100s f2 ISO 200 on both lenses, the 85/1.8 G photo will be underexposed by 1/2-2/3 stop. The reason is because a lot of the light entering the lens isn’t making it to the sensor plane, thanks to suboptimal coatings."
