Charlie wrote in post #18353967
FYI, the Fuji 56 1.2 is actually heavier than FE 85 1.8...
The 23 f2 also bigger and heavier than the 35 f2.8
I get that these lens will behave similarly at their maximum aperture as far as DOF is concerned, but the Fuji lenses still let in twice the light.. to it's given sensor.
Charlie wrote in post #18354183
I'm just comparing equivalent amounts of light, considering the sony sensor lets in twice the amount of light compared to the fuji.
lens listed are equivalent FOV, background blur, and total amount of light.
The Sony sensor doesn't let in twice the light. It captures twice the light on the sensor. Another way to think of it is that the FF sensor is twice as good at capturing available photons but doesn't help throughput at all. Your "total amount of light" doesn't help photographic speed.
Charlie wrote in post #18354327
you'd have to compensate the ISO to match.
Fuji + F1.2 + ISO 1600
would need to be matched with
Sony + F1.8 + ISO 3200
Assuming both are the same T stop of course. Both would produce similar amounts of blur and noise.
My original reply was pointed towards corndog, who made the claim that fuji was smaller and that sony provided minimal weight weight/size savings.
sometimes, sometimes not is the answer, and I came up with two popular focal lengths at the top of my head to counter the claim.
now if I start comparing the rest of sony's smaller gear such as the 16-35, 24-70, 28-70, 18, 21, 25, 50, you'll start to see that the fuji size is more similar than not.
The T-stop thing is irrelevant to me because the transmission ratios among similar focal lengths and designs will be um, similar. A faster lens, all other things being equal, will still allow one to shoot with less light. The comparisons you make do have merit though, but the perfect equivalency thing I'm not quite buying for there are other variables. Granted some may favor the FF sensor, some may not. Vignetting and lens complexity come to mind. Harder to build a lens that corrects and illuminates evenly a FF sensor than an APS sensor, while maintaining a compact, light design.
If one does accept your equivalency argument in it's entirety, then you do make a good case for Sony FF. As an aside, the Fuji prime lens offerings are very attractive for their selection. And the moniker Fuji will always be way cooler than Sony