>>4105396>goes on to rant about etherWhat a retard
It's because every single piece of glass steals a bit of light intensity, reflects a little back and scatters it around, no matter how perfect it's meant to be, as does air, and a speck of dust, and colors and contrasts wash out a bit by the time the light makes it through a 50mm "prime" lens designed like this. No piece of glass is perfect. Ever. No coating is perfect. Ever. In the quest to correct the image perfectly so not one micron-thin line gets blurred into oblivion everything gets kind of equally fuzzed out.
When I shoot with my pro zoom at f5.6 and a rough 50mm equivalent I need a longer shutter speed or higher ISO than I do with my older 50mm prime at f5.6... because it has 1/3 as many elements. The light meter is accurately determining that less light is making it through the massive "fast" zoom even if it's equaling the 50mm prime's field of view. If you look straight into any large pro lens you can see light bouncing around and back through all that glass. It's unavoidable. Complex lenses are vampires.